Coaui !/\/a^h Mcthooi^ % A STUDY OF BITUMINOUS COAL WASHING METHODS BY THOMAS FRASER B. S. University of Illinois, 1917 THESIS Submitted in Partial Fulfillment of the Requirements for the Degree of ENGINEER OF MINES IN THE GRADUATE SCHOOL OF THE UNIVERSITY OF ILLINOIS 1921 ' i I U‘ 'i li' ii; ‘U. y Digitized by the Internet Archive in 2016 https://archive.org/details/studyofbituminouOOfras TABLE OF CONTEITTS Page Suimnary. 8 Acknowledgement 11 Chapter I.- Introdnction 12 1. The Objects of Coal Washing 12 2 . Advantages of Producing Clean Coal 13 3. Advantages of Using Clean Coal 16 V/ashed Coal for Coking 17 Washed Coal for Fuel. 19 Cost of Handling Worthless Material 20 Effect of High Ash Content on Thermal Efficiency.. 22 Decrease in Capacity of Plant Equipment 24 Chapter II. - The Composition of Coal as it Affects V»ashing. ... 26 4. Structure of the Coal Bed.... 26 5. Chemical Forms of Impurities in Coal 31 6. Physical Forms of Impurities in Coal 33 Impurities Structurally a Part of the Coal 33 Segregated Impurities... 38 Chapter III. - Fundaimental Principles of Coal Washing 43 7. Effect of Difference in Specific Gravity 43 8. Settling Ratios. 46 9. The Natural Middling Product in Raw Coal 47 1C, Relation of Specific Gravity and Ash Content of Coal, . , 51 11. Relation Between Specific Gravity and Sulfur Content. . . 52 12. Distinction Between Coal and Refuse 54 Chapter IV. - Developmai t of the Practice of Washing Coal, . . . , , 59 13. First Methods of Cleaning Coal With Water 59 14. Early Hand Jigs 61 15. Mechanically Operated Jigs 63 16. Early Development of Coal Washing in America. 68 Chapter V. - Modern Coal 7/ashing Machinery 74 17. Jigs 74 Principles of Jigging 74 Jigs in Present Use.,.,. 78 18. Trough Washers S2 19. Concentrating Tables,.. 84 The Campbell Washer 91 Page 20* Classifier Y/ashers, 94 21* Cleaning Coal ly Oil Flotation 96 Chapter VI. - Methods Used in the Examination of Washers 98 22. Standard Metho ds 98 Chemical Analysis 98 Screening Tests 99 Sink and Float Tests 99 Sampling For Sink and Float Y/ork 112 22. Efficiency Formulae 117 Lincoln’s Formula 117 Delaraater’s Formulae 118 Drakely’s Method 121 24. Methods Used in the Study 124 Chapter VII. - Coal Washing Tests...., 128 25. Outline of the Experimental Work 128 26. Equipment Used in Experimental Work ..128 27. Comparison of the Work of the Experimental Table Y.'ith That of the Commercial Size Table ,137 28. Tests on Herrin Coal. 138 29. Bon Air Coal 145 30. Tests on Clover Run Coal 154 31. Tests on Y/est Virginia Coal. 163 32. Indiana Ho. 3 Coal........ 178 Chapter VIII. - Conclusions, 187 33. Sulfur Reduction 187 34. Ash Reduction. 191 35. Disposal by the V/asher of Particles of Various Specific Gravities 197 36. Efficiencies 203 LIST OS' ILLUSTHATIOIIS Page Pig^ 1. - Rediuction in Heat Values Due to Presence of Ash in Coalt •••*•••*<••••*>*••• 23 I’ig, 2. - Specimen of Illinois No, 6 Coal Showing Banded Structure 27 I’ig, 3. - Specific Gravity Analysis of a Washable and a Non- washable Coal. 49 Fig. 4, - Curves Showing Relation of Specific Gravity to Ash and Sulfur Content 53 Fig. 5, - Yield - Ash Curve, Table V^ashing Test on 0” - Coal , 58 Fig. 6, - Early Step V/asher Used in the Tarand Valley 61 Fig. 7, - Hand Jig Used in France and Germany in 1850 62 Fig. 8, - Luhrig Nut Cos.l Jig. 65 Fig. 9. - Luhrig Fine Coal Jig 67 Fig. 10.- Types of V/ashers in Present Use 81 Fig. 11.- The Laboratory Size Plato Coal V/aehing Table 85 Fig. 12.- Underconstruction of the Plato Table 86 Fig. 13,- The Deis ter-Overs trom Coal Washing Table 87 Fig. 14,- The Campbell Bumping Table as Used in Illinois 92 Fig. 15.- Model Robinson Washer 94 Fig, 16.- The Delamater Standard Sinlc and Float Machine 101 Fig, 17,- The New Sink and Float Machine 105 Fig. 18.- New Simk and Float Ma,chine Dissembled Shov/ing Parts. 104 Fig. 19.- Details of B arrel of New Sink and Float Machine,... 105 Fig. 20.- Curves Showing Variation From the Mean in Duplicate Sink and Float Tests.. 116 Fig. 21.- Coal V/ashing Jigs in the Laboratory of the Mining Department of the University of Illinois 129 Fig. 22.- Hartz Jig Used in the Experimental Work.... 130 Fig, 23.- Coal Washing Tables in the Mining Laboratory 132 Fig. 24,- Coal Washing Table Showing Special Equipment Used... 134 Fig, 24A. - Coal Washing Table Shov/ing Special Equipment Used... 135 Fig, 26.- Specific Gravity Analysis, Herrin Coal 143 Fig, 36.- Theoretical Yield Curves, Herrin Coal 144 Fig. 27,- Theoretical Yi^tLd Curves, Bon Air Coal 148 Fig. 20.- Theoretical Yield Curves, Clover Run Coal 157 Fig, 29.- Yield Curves, West Virginia Coal 0" - 3/®“ Size..... 171 Fig. 30.- Yield Curves, Y/est Virginia Coal l/Q" - Size 173 Fig. 31,- Yield Curves, West Virginia Coal - 3/8” Size 17 5 Fig. 32.- Theoretical Yield Curves, Indiana No. 3 Coal 180 Fig, 33.- Flov/ Sheet Deister-Concentrator Company Testing Plant 182 Fig, 34.- The Distribution Made by the Table of Particles of Various Sizes and Specific Gravities 201 8 A STUDY OF BITUIdlHOUS COAL WASHING liLETHODS SUiCiARY The experimental work reported in this study consisted of the examination of five coals from the Eastern and Central fields to determine their washahility, and the examination of a nxmiher of washeries in the central field to determine the -effective- ness of the methods used. The coals used in the experimental work were from the Illinois No. 6 seam at Herrin, Illinois, the Bon Air seam at Bon Air, Tennessee, the Indiana No. 3 seam at Terre Haute, Seams “C“ and '*D“ in Clearfield County, Pennsylvania., and the Eagle seam of the Kanawha group in Boone County, West Virginia* The direct object in the case of the three coals frora Tennessee, Pennsylvania and West Virginia was the reduction of the sulfur content to produce a coal suitable for coking or for gas manufacture. The other two coals presented problems in the general reduction of impurities to produce a better coal for the market. The general scientific object of the study 7/a.s to deter- mine to what extent coals of the types represented can be cleaned by washing and what are the characteristics of the non-washable coals which cause difficulty. Three of the samples were submitted because they present- ed exceptional difficulty to sulfur reduction. The West Virginia coal contained a large proportion, 40.5 per cent, of its sulfur in the organic form; the Bon Air coal, thou^ low in organic sulfur. ctiiofn r’' .... . ..i \ L '.■ .jk'”- i '\’'*» *>. 'j" Ji’zrr . *t. . . , '. 0;J oii -T* ***e j : « : ; * \t ii YJiA^: " ' O'l ■*• «•' \/l y.s\ ^ t ■.. '-;jt -* i ■' ;J. _■ - ' • ^ < • il V »’ . . 4. I *'; , . Lv' . '-i:'' ' f I' CKi . ?> ^ , • 1 - ' . >... , ,i ~ j > ' .1 ' IJ *.T , .'.• ' '--D ^ 'J-.'i/' fri a*'.' .''/r ? C’C - '•/.I tr\ ■ 'rV.'* ft ' * • t It \ r ‘ ., :t .v-i,a j " :vnio^ '*■ 0 i , ■.. r"*'*"' .'. o ^ Id mXj'.oc. ;‘ti ■'•<' .v.'tv-not'r ni-X ! fjfjs . 1 :'' ’ » .. ♦ > .-lo. •' '.U; 0 *D tIJ • - •" . <»3 f> r': ■ t ?4 -' I . ' l -tj: . •■'jf 'TV'.’ ' -J' Y/*- ^ ■; ‘.;rrc ■' 1. ■r Ui. fTO^rr J- T ' r.l wqI fl^JOfU . , -ii.'; an •i « ;. . 4 'sd 9 contained an exceptionally large part, 37.6 per cent of its sulfur in the form of fine particles of pyrite disseminated throu^ the coal and the Indiana coal was high in "both organic sulfur and fine disseminated pyritic sulfur. The v;ashing tests shov/ed reductions in sulfur content Varying from 12 per cent v/ith the Indiana coal to 63 per cent with the Pennsylvania coal. The results led to the following conclu- sions; sulfur 1. The 0 rganic^content is not reduced by washing. In some cases there is a larger percentage of organic sul- fur in the washed coal than in the original raw coal because of the concentration due to removal of inorganic mineral mat ter in the refuse. 2. The difficulty in removing the sulfur from the coals which were designated as non-washable is due to the presence of a large percentage of organic sulfur or of fine disseminated pyritic sulfur o|*, more commonly, of both. 3. The easily desulfurized coal contains a large proportion of its sulfur in the form of pyrite deposits which break free from the coal and form concentra table high spe- cific gravity particles. 4. The sulfur and ash do not always occur together in coal. A large amount of heavy mineral matter may be taken out and still leave the washed coal high in sulfur. 5. Difficulty in removing the ash from a coal by washing is due either to a large percentage of middling con- sisting of boney coal, carbonaceous shale or mixed particles of shale and coal or to a large proportion of fine inherent ash distributed through all the coal. 6. In washing a ravr coal containing fine material the dust is not cleaned. If the coal contains a large amount of clay this goes into the sludge or fine washed coal so that it may be higher in ash after washing than before. 7. In treating a natural feed of a wide range of sizes including the dust on the concentrating table the loss of good coal in the refuse consists almost entirely of large particles and the refuse in the v/ashed coal consists of small particles, mainly dust, throu^ 100 mesh in size. 8. In all the table washing tests the coarser ma- terial heavier than 1.80 in specific gravity, was almost all IT : t':: . j i f, ijv'U r f j£vv Ota ■I * ^•4.V \ -iJt ■ .-■ mi or^ OCX 10 removed leaving from 0.4 to 0,5 per cent in the washed coal. This percentage appeared to he about the same for all the tests regardless of the proportion of this material in the feed. These results were secured on coals ranging from 7, 5 to 30.0 per cent in ash. As complete a removal of the heavy fraction of a very high ash material such as a picking belt refuse or an Alaskan coal would not be expected, 9, The washed coal generally contained a smaller percentage than the raw coal of middling particles above 1,45 specific gravity, but as a rule the proportion of middling particles of 1,35 to 1.45 was no lower in the washed coal than in the raw coal. This refers to table washing tests in v;hich an attempt was made to secure the cleanest product possible even with considerable sacrifice in yield of v/ashed coal if necessary. 10. In the tests, the concentrating table was found to be a little more effective than the jig in reducing the ash and sulfur content of the coal. This is largely due to the fact that, at the fine size to which coal is crushed for table treatment, the dirt particles are more completely de- tached from the coal particles than in the larger sizes at which coal is jigged. It is probable also that the table makes a closer specific gravity separation than the jig. 11. In preparing coal for coking, where fine size is not objectionable, the ta-ble may be used to advantage. In preparing coal for fuel, the greater reduction in ash and sulfur is more than offset by the disadvantage of fine size. 9 ^ I , ■ K . ' JL' . . • »; - i.--> ;i» ■ j * , f :• • ■ l k. i .t* iwr ■•x:: 1 • v.io ^ I :.A T.' • .r <1 ‘ ; 3 _• ••’ "■ \ .1 i/ L^oo bv'i - . i ;. ' .'j X »f lO *• ' ■c'. . r'XLft ' ; ■• * ‘’X ■..‘■'i'.> or r_ 3 ^1/ ■ ': M flolti . • * f . r 11 00 s rr-*'- <3ltf42'Z4: * ,'. t.lv .,•: •» , • -^ v o^f ■v>.n • 'j ©’■ .■ -J 1' '* y .V ' ‘ J J l^t' ..o f i \ S**:" ^ -■■£ • i •• • •■) . j 1 I i 'f ti ACKN0WLEDGEl'i3)HT Mr. H. F. Yancey, Assistant Chemist, U. S. Bureau of Mines, did the analytical work connected v/ith this study and work- ed with the writer on the experiments conducted in the field and in the laboratory. Professor H. H. Stoek of the Department of Mining Engineering of the University of Illinois, contributed valuable suggestions in the prosecution of the experimental work and the ar- rangement of the ra.anuscript. Mr. E, A, Holbrook, Assistant Direct- or, and Mr. George S. Rice, Chief Mining Engineer of the U. S. Bu- reau of Mines, made many helpful suggestions. To all these grate- ful acknowledgement is made. .> \ V ‘X s \M h f 'v . ' 4 ^ ■ ' A < i. K it . : 'rariiiir oj”.' t \ < J _j J 12 A STUDY OP BITUlkTINOUS COAL WASHING METHODS CHAPTER I INTRODUCTION The Objects of Coal Washing * The practice of washing coal to separate it from the inert mineral matter which is found associated with it when mined,, constitutes an industry which is receiving more and more attention as the necessity for utilizing the deposits of lower grade coal becomes more apparent* Briefly stated the objects accomplished by coal washing are the concentration of the combustible matter by the removal of particles of heavy ash-forming minerals such as shale and slate; and the removal of a part of the sulfur and phosphorus which, are detrimental in the use of the coal for metallurgical coke* These objects are accomplished by taking advantage of the fact that when particles of varying densities are agitated to- gether in water they stratify arranging themselves according to their respective specific gravities with the heaviest particles at the bottom and the lightest at the top* Shale and slate being higher in specific gravity than coal jnay be separated from it in this manner* The equipment used consists largely of machines and appliances developed in the ore mining industry for the separation of ores from the barren rock mined with them* Ore concentration and coal washing depend upon the same principles and are similar Jti' h r M rv. .i ro n. V 4" t I HSTlAHt) * *:5> #1.- , ^.r 1 '" » T ■. -:. . >zS^V ItS^ '.^I'/L c T .: -.ol-' v.^.-.r l./.r.tL Ji^ni «rti •at':'*. Ji r,’ ' v4? : ■ . :.;■- '. z\r' ■''X .u:- aiv*.; :J~r.<. , , ;l« ; '■' 4' . , :i i?r i* ■,.• i, :ija i :;i . -'a ir bi. >.* rtoi.c •^: (^lOC 'V .. •■ ...: iviy,<'l t jT'. -L, •» •':* ', '. l'».^r ' iJ- w ■'*: . ' ‘li/ uCxJ :;? .i00ii^3 a'i< r’l.i M rj. .i.t.; aji .r'/£i ai '.t 'i, , ;7^n(Iitr:L“- .i^ ’to 4i r^',; ^ i ' f. jiu; 'll* 'h. et'J *io ;q “5r, _i,jsy! •. ; 1 Xo:cr' To «r': ^ *r^7i)jx V ’’ .'''Sriiicjino'o . 3*i . ^ -? 6^ •• iwic.-Jc-Vi V,- ■‘i'3 1 . :;i>'iv, +i ‘ / .^*. .. /' '■.. i '•*: ; t.v iyr;vXc*u':.-j.. ■ ;,:;t?:..i::'--'; 4 \-'4 1 nl tUltfJf':; -■--T: .: =. • riitv l oi ilx>aqv ^ oc-jiCT tC ■ V .* I '. 7>. i 'r£i ',1 ■ ir;ii,\ o'rt: orf« c^i S\qoXsv >^ ■.•j;;,'jjiii > L J I. ’ • •' I •• - ;-t.. i? iU_iv x r '*it sq'io 'to 6liS dx><.i-J ;- t»qt^ V !j,.’ X ri;; i:(" 4jl ' 15 ■ operations with the exception that whereas in ore dressing the val- uable concentrate usually constitutes the heaviest and least bulky product, in coal washing it is the lighter and bulkier material which is saved and the heavy concentrate is the refuse discarded. The development of the coal washing industry in America has been very largely in the hands of the iron and steel manufac- turing companies, who have acquired coal lands and mined and wash- ed the coal in order to assure themselves of a supply of low sul- fur coal suitable for the manufacture of metallurgical coke. Some of the coal mining companies, which produce coal for the market, have followed this lead and installed washeries in order to pro- duce a more marketable coal. 2. Advan tages of Pro ducing Clean Coal . The sole purpose of the coal mine operator being to make a profit by his operations, and the amount of this profit depending as it does very largely up- on his output and the price which he receives for his coal, it is obvious that any method of preparation which will give him a de- cided advantage in a competitive market or which will enable him to sell his product at a premium should be of great value. By op- erating a washery both of these advantages may be acquired. A cleaner, better looking, more salable coal will be produced, which may make possible the operation of the mine when others in the same field may be idle for lack of orders. Small unwashed coal, the market for which is practically limited to the operators of large power plants equipped with chain grate stokers, becomes, after washing, readily salable as domestic, coking or steam coal. At one mine in the Williamson County field where a washery is operated^ practically all the production of three z -.sae -ir- M.- •- -W- 't .liSsrs*' >7!ic- *'y T -4 ' r ' ■ •■•* ^!u.'!. J i’jf J h. , >: .: >0510^ -J ■ •'■" ‘t-’^ .. • ' -^il U/'J cjj Jti ;{f 3 , :- j if : 0 n o ^ '.'' *-• u C‘ r»tJw rtiv^ ..r .t^ric- .• \.Vr.« : Jb;- ^CT-. .:;! .-r -'ri.'c-, A :.i V-:: - r'. rw X ■- IJ- io ^ ^ ailT • V • r *1 ' » ^ f. o. J :c 0 'J X \.icv n»»(f e.*; sr •■•.■.1 '«r:lK ...« Hi r I<-9 'ni ; ;u .oo at»R . | t; Iv :■ ■- „,- .J. ,, , o.* *. yo : i, : .-(j t . . ^-^ «... 1 X- - o _,"• '< ^ r::3X,r J L :. f. It r^:lv X^w:} Ik *! oj T . * • '■ ■ 1 1..< j.-.J >caeX iK,r- .■-l-' oil-' .' f . t ®v:j.K |i ri ol 'x^Tf 5?‘r,c.- c r;:.. ■ S( ft #ntrr(, .' ; ris,. ■1.,.;^ :.,,i x . ■. «.v la ii !i ^ ' ' - , %» A i. ^ VI' X ^ X I iX. f ^ ^ '■CO r. Xci 'r I ;t <• ■' x^cirl'f o&X‘A<} 0,' J o .' / 1 vJ ..•<,' .f' wo '.‘X n-^- i* • X.'; £>’••: .' I'lrv — -xrj "Xo ':'oj,{v,» ' ii'! v^rrj, ♦■..tj r-.roJ. r-i" <*. ..ar r.Xrtr J; r--s.r -»vj- ' IX ■ f.i;00 '.c .'■.;- -.- -X -.;v6... -j V. .jur. v J ■>. 0 . !i;cf" .-uins-;;: .- J= :-J- i-, oX f* * ' '■** V-" '"».:J Ijp i • J * - - ‘v.T'T D. 7 __r.'i'r X«oo ? JW/.. . :.".n'../ ,• '.t-lOvX io.tv'«'' , :j v.r.o !| ni ■' i Xo ■; .• e.. }• aon Uy ^'o: * 'irj'xo lo 'XOi X - o r .-^ai • •f 0 iiq ^o.i -xol i,r* '.r-oo fa- fw; -.i;; XXn:?C ►. y< ,y [o •■Cj> fa*v - K'Juu.tq o;.*TjcX ::-roic'i?);qc"?rx^ cX i) ' i l£ I I * t ' ' C: ' 1 ■ «« X. , .ti^ti.'.-v tvX'-! ; , ... . ” ' • ■^i'' ■.'• ci O.-.Xf'i Oi.o w^/. . irc-'j-'x' 10 ' i.>fC'0 X, .^- iu /i. 90X IX 1 •••iscro 4I „■ ^ * ^ .i* 14 inch screenings with the exception of the No, 5 washed coal, size, is sold for other purposes than steeun raising. The number 1 nut is sold as domestic coal, the larger part of it being used for heating Chicago apartment houses. The No. 2^ , 3 and 4 sizes are used for by-product coking, cement burning and for domes- tic coal. In some cases the use of a coal washer makes possible the profitable operation of a mine in coal which without some method of cleaning could not be marketed. This is the case in some of the isolated districts in the west where the hi^ transportation charge on outside coal gives the local operator a sufficient margin to cov- er the cost of a quite elaborate system of preparation. The coals of Montana and Washington are largely of the type which must be treated by some cleaning process before they can be used. Tiie Alaskan coals also occur interbedded with shale and slate in such a manner that the coal as a rule cannot be mined clean enou^ to use in the raw state. While as a rule contracts covering the sale of coal on specification provide for the payment of a premium, often two cents per ton, for each unit of reduction in the percentages of ash below the amount specified as allowable, this premium is generally not sufficient to make washing profitable. At present the possibility of securing a higher price for coal after washing depends very largely upon finding a market for it in those industries, such as steel manufacture, by-product coking, gas making and the ceramic ^In Illinois the following sizes for washed coal have been generally adopted as standard: No. 1, 2"-3”; No. 2, l'‘-2” ; No. 3, i«-l«; No. 4, No. 5, I. \ ^ I .. I-'-'. . ..v.^::'+ uq':;,-'; •I'jriJo 10" ';■ A ^•.■..:.^'-J .‘i ?0 '■.-.''.-aI ®.,J’ , ;c*’ oij,'.'. tcN .'-i bJ.OA - * :. ) J j.; t ^ ^ . . ' .1 . ' ' c' . . X '1 . ;q>. I :ff.> vr'iv • -t _ brp;; T‘i :• L . Jn ' .’ V o J o : jOZ ■ - ' b *. s»i ::i5f;oc/ t^aataa tiOAi*Air Xijjn •> . -^^^0 oi J > tux^ z.ot< •:■ ?:'0C ft* •. , ;•.; -nt . 'to • :.t. 1 J 01 o^ilr^q i. f»:'r lo or.*:*) rvi '.r^*o s.-., .- : -i.lf.'” . , ♦» ■: r: !?.• .‘cu cluoo srlftr.eXD T.ir'' r: . I ■' ..: O. ^ \\^ j -rr .Z; o;*! 00’ 1“ *'i ’^‘1. ' :.'tj aJ *t X *X^qi' r.r;iL •;{! unVlJj i. >C0 OifX'jJi.'C .'lH ' wi ’.'. . ■, •* ’ • io riT-:»j' - rJ«i\ jo’-atf- 0 'X^,. I. ’■o .‘t- - •^;:^r •*,1;) ort);} vc 1 ?aw .::lf/ X “li'j .jJt tL':;:fC oniA . co \ <*"■< oj "'liL: AC' A / •jL t "/* 5 »*. X •' - ■ r s : : ■r'J *X r. n; . • ** 9tii hi I nc Xaoo 'r : -Z»e '^rt^h\'oo 8. • ■ -aXv'i jj . .t ^ n*)j V- , - '• ‘ ^ -j ■ V. ; ' tJ^i* 'f x * a : -^ r ■ .‘j vclc- ;.;j iO (.►C'|jai.':ori»q ni lai-pT *to w^irt-j Knxi* ':•.* , I ••-C-' -i . ;jLnvfjir/i n£ J ./c-.-x dd. *::t f ' --- - ' :^nocr<£_ .ir^;: . a $.X..- 03 ^s,^lxit'tiun \1-3V V 'V 'i j'i. I^’T.Xd Li X 'lo ■ ' ■ £i.i jfoxTf^ , ? -.v,* f^;. ^ - 2 ■ *: bl- i. ;;ni .2 £ ^-.c ■. >i'n . ':mo s.', ja;., :' i jji.;-' C5 a>*;^ ,^q}>Jar' Jyi'.ci ~v- ^ ,xj- C'.-'ti.f'tn* .'.'•''.is * li' : j; ^ • ,o5! ; 'v:-»' ^ -■. l«rAf ”?iC''i’I I [•■'■ ; '_ . , ■ 7 ■ ‘ ' '/h ■ ' ' I. X . , . . - 4 j. . t < < * • • { f" T. H -!i 15 • industries which require a low sulfur and low ash coal* That these industries will, in the future, have to draw part of their supply from fields outside the present restricted areas of production of low sulfur coal in West Virginia, Kentucky and Pennsylvania is becoming obvious. While our reserves of coal, which like that from the Connelsville district, can be made into good metallurgical coke without washing are by no means nearing ex- haustion, the big consumers of low sulfur coal cannot provide for their future needs by extending their holdings of coal land in ' these fields. Furthermore, their rate of production has about reached the peak, and cannot be expected to keep pace with the in- creased consumption of low sulfur coal in the metallurgical indus- tries. The deficiency will have to be made up by the use of wash- ed coal from other districts where inferior coal is produced. The rapid growth of the by-pro due t^ coking industry, as distinct from the iron and steel business, for the production of coal gas and fuel coke for the market furnishes an entirely new market for washed coal from the desirable coal/ seams of poorer quality. For this purpose a coal is not generally subject to as strict requirements with regard to sulfur and ash content as a coal to be used for metallurgical coke. The limit for sulfur is common- ly placed at one and one-half to two per cent. That the production and use of cleaner coal for all pur- poses would result in a great saving to the industries of the na- tion goes without saying, but the coal mine operator cannot be ex- ^In 1920, for the first time, the production of by-pro- duct coke in the United States exceeded the production of bee-hive coke. f « % '•m ”i M } x'ir f I t. r. ^i .. 4 . ,.i t/o'''*" **• . . ■ ,. , -"- > • -.i? 4 >;|r f»' ar?i !' f- ' * I ' SiLfb ‘r .1 '* -'; j ^ ^ ■ Cj •■V. • -J '.'.i t\- ' ' • i • ' j \i j . c » ; ;:t.:iiOO . •.: 'io ;•- • !*'C t.:o i 1 r^^uJiVc •;^-i ♦ Bft©** l 7 Cfc fc''" -•-J.: ; *• ■ 1 ; ■ .' - J l'-. :o 0 ©rf? '• i.-'i*'. i&r: . • ^ . ' r ■ ■ •< • -‘■’‘■J . . V"’ .' ^rfE*'-" ^- - <■ . • •/• f 1 J ^ ^ ‘ ' ' +^ '’X>'r..C: X;:i ^ tonrr^n .: r. ^.-:-;r t..X ^ ^ ^ _ | ^ ‘'■•■■f. £. :c. : iTjr.tio^ ^-:>•^ | ; ryb, ms'.r nci.-.utic'zrr : :- ^ -.n ^ '! “ ■ ' ,t V ' • ri - - .--T' 00 /- :• o I 0 ^ y??v:oc ^9 Jofui^b e*: ~ t 8 ‘ bc.'oy.e’i f; r ■ •X-i;H !,<:• , ,i T:^aj :jX , i-jix«dira 04.0 j! •'“' ‘ '^'' • •■•' ^''•- ' XX i"’/ . • o :»v.l . x'l . .I'l^ . ' -•. -i Axco -rr^-^Vt* ;-ri:%,vv xXox-Ui,xi, 0 i : -i , X>.,,a ;jo , -. . o.-io.njo '<•'■ -/ o -{^vEr.*x-_ oioo :• or^r ■r lo . K o . . cxq o. .’ 'X. , ifriiii^oi !*<•>,> e';io iim i - --rt ^ T j :! ^ L ^,,4 j ^-,. ;j.; ^ '-X? ■ ,ol 3 ,o'ii jj J CiCl't IroTv b^i'.D^ icl * OA^^.;'n - XD 9 ;,:},.'; \Lt - '.i^ j :ri a: I. i-o - o'ioo t.fr . ^j-iX /i/i' : ^5 X:-._suc hr.^ TJmua c o- o*: ; *, f.J irr rJoa ' ‘ ■ " ‘**'*^f ■•'•' «.j . ■•?«•'■ ^ i, ttjre,-T ‘tv* ,.*:i :>0 , f «. r ; •''« ‘ ~ ■-< ;>tio Jo ■ ' i 9 ^JsrXo 't^ - ■■ .., . nc/joj.ff)oi -4 ^ ,j >•• ^,-j I* - oJ r^roir^a Xlooe-: Mxfg- ;.p^ j . X J.;rx30 ./lo^h'icoi- ;io ixioc .©/fX 4.-V . i -/ :. j u(. :j - : e^OT. • boi J ■{ • * - -O'U.*. - 1 -: n 4 ;iJ.>;H.o • ■ - . ■ 0 * 1 ; .. , i.‘ .7 ,nj 'io'i , 'xr'Pf rri'X **•■ X ooLoaov© -iJ ri ^ t • • . i* • .•7 .. M. .Jipllr'z 16 pected to supply washed coal to the market unless it commands a sufficiently higher price to pay the additional cost of the washing operation. A demand from the users of coal for a cleaner product and a willingness to pay for the increased value received will make possible the washing of coal for fuel. The two chief advantages to the operator of producing washed coal are a wider and more dependable market for his coal and a higher selling price. These two advantages are being accentuated as the users of coal realize more fully the advantages of using clean coal and the great losses due to handling the worthless dirt in raw coal thru the cycle of production, transportation and utili- zation. 3. Advan tages of Using Clean Coal . The importance of this subject of clean coal will vary more or less with the widely different uses to which it is put. In certain manufacturing pro- cesses where the coal or some of the products derived from it enter into the composition of materials, which would be damaged by the ad- dition of sulfur or phosphorus, the use of clean coal is mandatory. The principal industries which require low sulfur coal are iron and steel manufacture, gas manufacture, the ceramic industries, the smelting of ores and the heat treatment of metals. On the other hand, to the great majority of consumers who use coal for fuel, the advantage of the use of washed coal is sim- ply a matter of dollars and cents. It is impossible to discuss fully the application of the problem of dirt in all the varied uses to which coal is put, but two typical cases representative of the two classes outlined above will show in a general way the extent of the economic losses which are directly chargeable to excessive im- I 1 ' * r 4 • Si \S ' jl|' ! . 'i, : •Diil'r’iu* ; • * V X 9 t* 0 ■t Ciic.'ji.iij: I’iv br. * ' W |^4 f! . '.«i .»0 31 ci. • 'I'M u:i: V.: 1 c 30 C ; 0 Jo r ‘I c"* J. .0 > : t>' -;C iJj "'.•’■i r'^r •; . • '-^qI - ' . ' '.t; V ■; X •? ,> U’i-tJr*; *. .. * ' _r>--jivjaev^i; ioiiu- cc^ 9 ^ bn I-;c:.: i- ■ •' /t. , f ;?*rc. - - ^.T• - .V- .. - -..sr : . iflifSli.i.. ■ .• = --^<”- - ' / :>rcu t>:;i.Xi*^v j < T«. ^ • q. * '’.••■ ■ “ ' ' *. •- ■ • ■• ■‘- oj ■.■.>i .* -T,^ fr*J j-0 o^ri.r ."j.iAi _ - ,:>:*ji;. -X,. io re'-*>^ r.. i :- ; . ■ , t-*- q-'i V ' , 2 X- Xl‘ i ... ft . r Ji*r “i . o : ,. i ..y J.ilw i:.oo.'r', .jroi " . i-: o ;*! ni ;.X i rto-r ' ovj'iob .. w L- “ t. < 4 ?ii 'T j Xoou >». c-'is*. ''.oci-r £fc> I }' -J •• A . •. , j. .- 1*1 0 : H„fT ic :t iJ 3 .. .. :c 0 . o. IJ ; j r. j « If 1 -r, ' • ^ soo nsoS, 0 to fti -X J- , ■'. > "i rvrtc^ to f. •> f s >.;.' .T(-r. '> 1 : '■ ■CO •:•'■;,- -cl o-xiio o-: ^-. r^/{T s li ^i/'i > :j . -. 4 . t ^ , ..^Xoalx; - , 'i:;- • ,- I; r, e ” - • • ‘ .. ‘ 3 (% 9 ft-: ri-Ll * ^ J ^ .' -. • a *’ » ■' w 4 • . 1.. 1--V .. ^ <..w«««.a • . fillet ... J .,;-r »r-j «. , , ' /» - ’. j: I«oi» i)srie/iv -Vo aajj.an’. .:v - . < vo.^ sr'-^ -iwl 8-'/ f ^ ■jMSJi^aX: Oi ;»J yianC-pTi el J ; j./: . a'SAUo»> :: ^ i .;!? o -Iq I iOf:/. joi-X.^iV 1 .! • -i J^lb lo C 5 ^^ul 4 •4 1r. XK-f^-Xio; : 4 , - J fa 1 - '».n 'Io ovi.^r.jj— .' 'f.v''-: i.r.B..0 lx:* Cro- ■ oj c J • -* • X T 'uto;-, -j :ii wo.'lB .Cii - Jbo.T. ■ ' y /-■ > r 4 , o c.' ftl 44 !>x*X 3 rio ftXi .‘■'rXd-i' ; :.i.-'^o.:o.' 3 a o^ilvS 3 17 purities in coal, V/ASHED COAL FOR COKING For the manufacture of metallurgical coke, particularly if it is used in iron and steel making, a low sulfur coal producing a coke of about 1. 10 per cent sulfur or less is required. Some of the Eastern coking coals, such as the Connels- ville and the Elkhorn, come well below this limit in the raw state, but with many other coals which posses good coking qualities v^ash- ing is necessary in order to reduce the sulfur content to this figure. In the southern and western fields most of the coal used for coking, though low enough in sulfur, must be washed because of excessive ash. In regard to the use of washed coal for coking Wagner^ says, “It is an unquestionable fact that coal washing will greatly assist in producing a high grade coke, as even a comparatively low ash coal will occasionally run high in ash and possibly sulfur, due to careless mining or to the irregularity of the coal seam, the washing insuring a more uniform quality of coke”. An example from actual practice will best show the relative advantages of washed coal and raw coal for making metallurgical coke. The following figures are taken from a report^ on results secured at the plant of the Nova Scotia Steel Company. ^Coal and coke p, 104. ^W. H. Graham Trans. Canadian Min. Inst. 1918 - 231. 18 TABLE I Coke From Raw and Washed Coals, Nova Scotia Steel Company }^aw slack Coke from raw slack Washed slack Coke from washed slack Coke yield per cent 64. 5 62.0 Volatile per cent 35.0 38.0 Fixed carbon per cent 53.0 81. 5 58.0 93.0 Ash per cent 12.0 18. 5 4.0 6.6 Sulfur per cent 2.0 1.2 Since the heating value of coke varies with the carbon content, this shows an increase of 14 per cent in calorific value of coke from washed coal as compared with coke made from the un- washed coal. The washed coal also contains 8.5 per cent more vola- tile than the raw coal and will therefore produce an 8.5 per cent larger volume of gas, neglecting the amount of gas occluded in the coke. The washed coal de-ashed to the extent shown above produced 4 per cent less coke. These advantages lead to a further advan- tage in increased oven capacity, in weight of actual coal coked, volume of gas produced, and effective carbon in the coke produced. The decreased capacity of equipment and the increased cost of handling throughout the cycle of operations due to the use of coal containing an excessive amount of worthless ash forming minerals is apparent to all, and the losses accruing in actual op- eration are usually greater than the theoretical calculations in- dicate. In the blast furnace a ton of coke from v/ashed coal gives 230 pounds more available carbon and 24 pounds less ash to be slagged than a ton^ of coke from unwashed coal. Thus a smaller a- mount of fuel is needed to maintciin tl'.e required temperature and a smfiller amount of Ime is needed to slag off the impurities in the • Ir I ■ i ■ . ‘ ■ ■ •< J 1 .V I 4 . *) L h ' ' ■ '.L ■j.. :•> .7 - . -i^q i> t' - ' • . ■■ . f t ■ .. t ■t ■ ') ) ) l'J < 5 #-> ' ) V I ■• ’ ; j > i r» X A. X J :.f . TJ:-" / :; .. -L' .'I ■:> f i ■' rc-'^ oi ■( r I r ■ j ) .. o ■1 o:^ ’.'I r * j 1 .. •; >-■ J 19 coal. For this reason a much larger amount of ore can he charged. Perhaps the greatest value of the washing process as ap- plied to coking coals lies in the production of a coke of more uniform ash and sulfur content. It is possible to produce good pig iron from high sulfur coke if the ri^it conditions can be main- tained in the furnace, but temperature control, always a difficult thing in blast furnace operation, is impossible with coke of irreg- ular composition. For instance if the charge is calculated on the basis of 1.20 per cent sulfur and 5,00 per cent ash in the coke and a batch of coke containing 1,60 per cent sulfur and 10.0 per cent ash goes in, as soon as this coke of lower calorific value reaches the re- duction zone of the furnace, the chemice.1 reactions are arrested, the silicon goes down, slagging of the sulfur is arrested and a __ cold furnace producing high sulfur white iron is the result. On the other hand if Uie charge is figured for coke of 1.6 per cent sulfur and 10 per cent ash with the ri^t proportion of lime to flux and absorb these impurities, and a charge of good coke goes in, the furnace gets too hot, the chemical reactions are intensified and an iron too high in silicon for the basic process is produced. These dif ficulities cause a great reduction in ca- pacity of the furnaces and a bad slag as well as impure iron. Grfihem in discussing the effect of hi^ ash in the coke says, •’In a furnace producing No. 1 basic iron, the loss of iron in the slag increases from 1.0 per cent to 8 or 10 per cent in a cold furnace**. WASHED COAL FOR FUEL Primarily, of course, the increase in fuel value of a coal due to washing consists in the increased proportion of valuable .•o^j ri-ju.XL » iir ; ?90 ..>ox-T t > ^ ri/^ - ■»•■•..' *>* 17 : S(!l ! :>•■.. >0 rj o^o^ . ic t'lv.ro'' . i. usil aX^Lor t ' <>111 b ;oj^ nr.'f'' tvK )Xii?coq j ' , -xir'i* . . . ,n . •, iriollni' ;rt ;!-0 — ^T Li ojLdo A . - . ac-xl^^lfr 1 ,^^^• i : r .'M 1 , ■.. 1 4; ^ .^-rA o jnij/l %'^A Hi ror*’ ■: -.'.Ti ?: • '3 v-v <^X ' i <>60^113 1 , vw"* lO;^© 7' ij J .llxi? ^ . lllooi^oa 1>X« L-': f , _■ :-' 4 c' nc : ■" " 0 1 •■‘X •♦3‘If '‘C 'B. t 1 1 'r L loil b. w , -x ' • ; ; 0 0 ' “‘V* .y-.,- •cajj'j;, jb:;j ir»f'CS.I la >a 'i . •'-7 iC.'H » * i‘.tl '.laoa d^Pd.'xc • b'-aioOV •■• .’I •V •. i r j •t X l>f» 'XO vol 1'.. '»!!■! i;y iJ s*v bv oe , *»1 * i / i • ' i 1. >Xr' | 4 > If^ /•• '• 'oiLz ^0 esos m>iJot/b ; :•! a ai'i A -.t 'Ui'i U; :- -N ’ j -■ 'to gni r '’oo». iWdi ‘ 1 J 9X1 ai no'ii •:u"i 1 8 ri^Xrf ^asaxr.a iXOw ■> “ ■-• ■ . . j '■* *•. 1 ^ : a. 0 a ■ u >n: .'l 1 .:io i'.'J' !iO: I iTci^ i (i-Xj-C ’ J.' ..- •.* .-'.‘ir ‘iQ-, .fn90 i^q jX ^-.v.i- Jaso liOGj.' :r ':.. -in - ;•,.. , ' . '.^ i iicoi fri X^ri j ?::,'C'l 7tiUI 'ic i ::. oX 'o :.«*r ' -jl rro-^fri e^^il ,7 0rt coj -ictp a:; .ii'iir'i 5'i ,‘A oeo‘^ :jXuo -■ '*^ -•.i-.'«-:c-r: ::1;;.;,J g,/4 .JQ-J n .'IXliJ rtl ooi aTi j.-a 5)Cr^^i;' .^lai 1 '} - -o ;<1 xxjjs^i" lib a-a. ? .^.'^ouaO'iq s^i f! • J ■ T t; . 'Tx. -a/j*: .1 , ? L’Xow a- ilr> 3 tirt« a ■'Ofixiifi ‘jAZ ,y,i Jto^jq 1} ... ■ ' ' , -3rsi3 c. -. 0 '. <-"(. i '^.,iA io 9 dt -.i.-) >iX ii iiloTO jj • '.) .-.i ;:o-X' ■•■5 aooX •■•;.; , -oil oic.:.. X .b.: ^.r.i'': w'x'i 'bJSaaJ'T a '1 ly Z bXOO JB .;.i.’'^..a3 lOCr OX "T. <. .< oi 1 iff -C ,L . ' . '■ ’0‘15^'i 7^', -»■• I /-■.•, T/ ■ r\ r--r- ri ■ ' . .- ' ■ . I.' • LI ^rf».- t* .>.*-*^••01 11 Jr. -.j r.i,i i,-i5f!aLf DHu i.y; ic'i I-.o::; - -j o.‘ ■ «« o.T ( nfr> j ; ^ ^.-XT.aw . ^■.i 1 *^' Civ.ii"!‘.i .' ' ' -T rrf.'xl *,i'’ i ■ * r*'*’’ ,, r i ,.1 i , . ... ^ .i l-i-'?..,.'. C,inow to >««0 e , ■ ratrfo e; ■-■ •-' on. ;c i- .ni- ... f .u,-,- .j., ...93 t..,, :■ X. J ,, : t ■ 1 :j .t aoa»(|^cd ariif toroo .1 Bfcnf! ”' * ■ “■* • - V... r: .••<’':> , *Xt:i . ( v.jIT .'tv'i-Tjf;) tj Vw ’' /.r .,'.1 Tjt. .rjv 3 ^• ti 'T^VtSrL ‘ «a n£d 3 r U 4 .I'? * J JT .f ; 4 X,. ;^nxi}i •: 7 oT: ii • ** UT 'Xiic.'y Oi 9 .,’,';:; Oftt . - , X.ost'>X ,» X ‘ 7 ‘j , .1 '^c t-' j :iaa T 3 V Tovis . ' ; V «ut't at) jisn TO avow : j o . V, I X . t ai on i X r r '1 . i! i. 4 . .'. '■C'L~' s^‘.;.'.) ’X*!., '• . ’‘'J *■. t: Ou: v.-;.rrnn 3 ;. , \t 90 i , _ j, bit^ . , I .OX 1o . I; , :! .J . ‘ ■•^■» 't {*•■:: Cx i' ■. rt..^- -jXt'uV'oaH: „:'(i io 69 ji ;! - T.'-.- i'jii .w ’'^jo ^- . :o ^ ' r,?r!oo 'je'il 1 , I .'■■-•■ : - 00 . 'f.* r?f .>. « ‘'^ .xo-ct ni ?'u ;x c- 0 • ■ itoXJix»£)J# aX ha ,i , -. '..O'i vj I 'las'T.'i I-..UO ’xol *'T“: ,'..;?©*i.:ifriV' 0 (t 'rojx L dua. '.'lani. ' ''“'r Xt,oo “ii A*%«n -; «»;•. r'.t.'a |>j>pv;';3i^9ni ,^nitlq *> §.« ■■ . ‘ '•■-/■^Jab b'TUiu.di^XKii X.ic ■ baa, • , ' !!• •J i l-.:oo 'Ort ,-7 ;- ,*,( ^ c.:.’ X'rV.' •; .^a:s?'j„Xa 5 ‘ x.-^Lfis r," ’. . .j.J.; ^ [.sa:; \i for useful work. 16 18 2 ! f^eductfon in deaf values due to presence of Ash in coat. {j\ -sigto zV^\ f ^ V^ Vfiorvtv'^l^ ' 1 i W\ zZi^l Awid i [. \u*t^2u 'vi^ V ^*5ir ■ * V-'^ (c: : J>_. ■'“i'*«^ H’^'7 ft ’' ' Z*av)\ r>n!:,-ifl 0 j 0 *'ts 9 >. . r''^;:r 7 uJ J 7 '* r-ii:;! , ’'V.;. I . :•> oj :.»L‘ -iaqo . jrjuTf .-. • ,, XT .-Cl ‘W C. * 5 :“ w-b-.i^‘JO A i'.i i r\lAiZ o: ; f'> i :ti . : :; i gCo to i s , w ■ o G .C/roo Lli* 92 C'l’txiorf XOW ? • BOIa ^ ■*, ■-. > T /;i r V -v;!/ *' n-r 0 ocJ .’>., ,-f Xboo e:-i wner /iliO t.-'..': »'» ' (:« ;';u i.3r.' V'X rc -■-a ft'i '-j '"^“:;:*!i" •-! ■ 0^ 2,33 /is i . 't .- ', 1 a Cf rfr>U.'5 G£ .'.•xlJ- »3ir ‘ b- tr.«lX : r.' li- . j 'V: 1 j 'L, u'! J *' i , — <0-33 oitXx-«q3 OV* SO Off? ■ ’ '- ■ ft !>: J. f' ■ .-■ ‘‘'J.Ci w j -C-’Q*' 0 lo ^azj i>ni -x.^ Jc nr^J Isco ’t b "•Gt'i.'-'joi •:. 3 'jT •/ ^ oi..* •;?. . . ^ • *i • •■'J' :.'',--I.'*iO Xliv oiloo fi <1 h A to 3 ■ ' J'£,.:(TO-l , c3TX ;.. .30 3ii .Ori ; - . i i'-' i ti«r '. c. C ; 00 't 0 II ' ; hIl' ’ 'I-V'lJ . ^ ‘3C '"f^S £?'l'. 'V'i .' 3 V.'; : .rl 1 li ;! *1 Xa M 'C-X •..n;i -.1 0 Q,'.'i 3 .;t_ -.1 liiQO .'to J- %yq c- * : 1 ‘JiVliHi 'Vi -...ul-v -jiyJ oJ «»:‘.i . i;t3G.:^T • - - ■ o jJr. ‘i.:niul.d x^.^ ■ 5 X 07 t‘‘‘ua *j v;'i ^ J""; w c-v ti ,o.tt ■■ 1 *• if‘n*)r'7^oo Ov iii *i .'‘k ii-.w r: o'tl X^ioo wjri ©'■ ] 'lo yro^f^-, 'Tot ;■> .'>4 3 r,:!iJ S^otjo to -I'.-GOiTXO 'j.’JT -ret '£CJ3'£OCJO a.u - ^ Vx rTo3i3 Yl-X'.rtC'. ...‘tivo'r;] ,«-)■; {/!«»'? o:ij- l.l ')^..>a;.OJ io-^bOj£ orir ' • > , /. ‘ . GX 99 SJ i‘ 26 CHAPTER II THE COMPOSITION OP COAL AS IT EPFECTS WASHING 4. Structure of the Coal Bed* Generally epealcing a bed of coal is laid domi in more or less distinct and separate horizon- tal layers or benches, adjacent benches being separated by the nat- ural bedding planes, which probably represent a temporary interrup- tion in the deposition of the vegetable matter which formed the coal. Sometimes a layer of mineral matter is deposited between benches of coal in the bed* Such a sheet of foreign matter may be only a thin coating of clay which was deposited on top of the lower bench before the layer of coal above was laid down or it may be of sufficient thickness to separate the coal deposit into two beds which must be mined separately* Between the well defined bedding planes which separate the deposit into benches the coal appears to be made up of hori- zontal layers of material of somewhat different structures appear- ing on a vertical section as alternating bands of bright shiny jet black coal and dull coal. These layers vary in thickness from a small fraction of an inch up to several inches* This banded struc- ture is shown in Pig. 2, a photograph of a lump of coal from the No. 6 bed near Benton, Illinois* These alternating layers of bright coal and dull coal are designated respectively as anthraxylon and debris by Thiessen^, who has shown by microscopic examination that they are entirely differ- ent in structure. ^Structure in Paleozoic Bitimiinous Coals; Bureau of Mines Bulletin 117. . > ... . - iriincAW \ ’, ,;• ::C't; l«f;iT . - ’ • - J V ■ f • \;il:Ls^ . Tor^O A’l »‘ oId ca S I u..- Ou i>f’ • 0 . 3l* v: 0 *5D0 ti '' e -X ■ Di j.'X V‘X ^'.r ’'z.\‘i^H. " .•i ,> ..' ■’o ''o,... j' ,X ( 0 •''. 0 • . 3 ^ X V - ^ .L "5 - ; ,. 'X‘J ■'X Til ■'"S,:*>'o- ' r'"* 3 J-r 5 '■• .'Dr;.- f*i " Z r:o ;pj- 4, . , .--tv.. ■J. X '£ r .';> i, ' roJ -' ■' ' i ''■' n l.‘ ‘lo .tox.U iOqob D 'i '"— -i ;;fC ¥’ no-- i t • ^.' ? . fi 1^ J ^ :.' : h ,3 ^ :.' t ' ax r.ioo 'ro '3 or(a r:"-j ■" or O-i* *> 0 -.;c X iTO :; Ji -f .T b * 1, • %(*>• -J w - ' ■“ -' io ■uviid’.i'oy (ti tj yJ[i-o? I t, » i* dJ •' '.aw v'ucTn'X' a&oi jvr.r cj -.i 'id 'X;; <. U ‘ DC'* 0'S O'! erf rfoi:i>M |j ■ Off* orfai iqoj .cj jI ilirr -\*, -Ji/’ 5CJ_X fj ''.:ai?rf J r;,''.* f '•: :i -05 rf* 03 .. .1 -r i^ov ' aoc .t \* .. Oi< 'i : .f. X'^Uv* 'Jn’v o^ai j/fe .' o X »»X .K y w ;oJ I iO & 'C DC: .[7 : J J'X;.'J Oa-'TJU ;; X 'I; •i.rfJ 1v. r:> .iX j\;: r .^J‘•l';D7 C *i ..poia o .--- T oiX'tr)'/ .-j '^Dx »■ xi ;iOx l/'!io;-;.f^,.l; Ir dx \'£ v 3X';.'c X onoff, . co j.:,;:,) ^;:v: S.^00 | -Q ■)c 5 J. "r ZOiJl 0 * 3,!x :.- iu .ioxjd ’i‘X Il.'iJ::?; r '< j IV':.- /-c:^ X.^oo Xu, <^'L ^4 *> j rfcjjr o oriu ■ , . .oJt'i- /;? a-=,:;;.o oi , r I,- ' . , ■-OX-^o j. T.. jj: ‘i ' I. ior» livh ,jbn‘: Ij .0 Xil^xT'f to *nxax'’X .• ./i : .S'. 7 0*7 o fir c. '.VJ ';a‘£ S: .:■ f;Xj.'*X4‘trrX ;: 5 . •.: J 'K j v"A J .v30 S/. j-iir- j rf 1 : -D;-'l’.: :• ■' oxj ^»nj X. aX .ao j e „aiir'..r^& oxcoo?.: o'y-jira ^ ”• -,V ■• ■*- .,T,^ • •• . . ' ‘ ■■ S . ■■„.?■■»■ D;/'iXn .. i Xns «< I c«':x’' 'lo t/ssx . e • ;Ix*or> c;.;oai-3ff.;ri . -oOfiX t.’: 3X. / n<' -rX® X [ f ■ .S ' -.r <'S-r 26 "The bright coal bands represent parts of definite compo- nents of the woody parts of plants; that is, parts once logs ofy' stems, branches, twigs, and roots, but now much compressed." The dull coal layers are composed of very thin discontinuous strips of bright coal imbedded in a ground mass of finely divided material, the atritus resulting from the disintegration of vegetable matter in tlie formation of the coal deposit. This banded structure has been recorded and discussed by various investigators since the time of Witham^ who was the first to study coal in thin sections. Very thin layers of charcoal, highly carbonized woody matter, are found on the cleavage surfaces parallel to the bedding planes of the coal. Ordinarily these are so thin as to be hardly discernible in the vertical section, but occasionally charcoal lay- ers of appreciable thickness up to several inches, are found. These appear on the vertical face of the coal as, charcoal or moth- er of coal bands. In addition to the division of the coal beds into hori- zontal layers most beds show one or more series of parallel verti- cal planes of cleavage which determine in a general way the direc- tion in which the coal face breaks in mining. Subsidiary to this major system of vertical cleavage planes or fissures in the coal, which is often characteristic and continuous throughout a given seam, the coal in place is traversed locally by a more or less uni- form network of planes of weakness generally referred to as joint cracks or joint planes, ^«hich determine to a certain extent the size and shape of the particles which the coal naturally breaks ^Report of First and Second Meetings British Assoc, for Advancement of Science 1831 and 1832. * • ■ s:c -.'..‘i . ntrr«!r; to a." CX »?J'r , i> 1 \, •* I y’^ocir v..: t . < '• - '• -r ; no r^Utrr^* -rci: ^ ; . ' . O'X v , i':- , , ,.:ol i •' •i*r;5 : .•-‘"’f'" .*t;^ vii'' ,;rv/ ’to ->3 '^.o rnioo oi : r : -, v',r*i Xj c? IX. • * ' . . 0;b:-. ,1:; Xl'lo ’>.1- : '>rtUOnr^ ' : ’ nl^/iObOo-igiu.^ X,-- 00 • • ''V/ 1 ,:t ::oi j -X J .. -x.* '-.t .* ’^■- - m ' * 'rr ... . . i;:T « .• Uocr>.o £>ioo 1c r>ot. * •. ru -I-:* * .i ' • . b> bri j /. ..oei no ■ ■ , . t .Ut *X I/OO X'»X'.’S oi J.ItI : r.'- .; ,.r I ' ■-• ^'‘7- ■- ' , . v"?'i .Jo. 1 V vi-r::,..-.: aiJx- 'c-reV ' ■ ' '^'*1 ' ■' ' -r;. ‘.V ;ji 2 .i>xU ,.o b aot ot ■ ,^o*.r ■•• '.'■' - Vi'- V ViO--;? / I.-.4C01 *' ‘ >'r •'i**-- •' .6;-. ...J -K ^3;LsXq f: ! • . r « O'.'i ';, : ■ icno JJ , iciJ;v; >i X*- o t^ToV o. * ' .-.i’ •. : Jx/tiojni b , r‘^0i3.L I .'t’r*:*v3 ->.• oi/ t»X i. -r nd^tijiqfe ic a x 3 < *• ^ i •' ■•'' 1 Xi*oi^‘ir>r r*'.-* na i > ua-jn'r r* I 1’o -■'">•■: r r,30,/ I^co 10 ..'Oftfivtfc '.. .: hi tt,t ,a -i-J-: - 1‘^rx .^oriu' evr.:. - o -r,-:- 3 ; . ; xi Uincs •,; .tr I J-T • ir^3 lU ” J v;» lo I.r-o i n,.Xr c* y*i Xb. «<:-■. nl ';.,.:e 7 ; •': I - oo oH3 i.oi > r:I noi^ ' ' * '■ ■'*‘•'23-1 ‘ raotj 1o ■:^:f! 3 \;a ’-''''■. '■ U.jC'%;.f XiV.'j or.ix OiJ«i*r3**Oo'l.w':o »;?' tioltih ,f . xo ' , ^TT j ' • X ^ ~ ''W»> » A '-/ ' i .. M ^ ki/ ' ■ X>->-' iO'J ~ oj 90 i iT’ -'ll <>r> .*:' j « 3 .', -. j. J. Vi r./.-c-.v?/.*! .f -^3 «'olrtw-oo.:i>J:iio<;* =»*-. to ©.;• .n ti.;« oxifl -.f yXI-.iObX btven9V;rt« .. •• f-o.::!- ri-X-..o OsL -HI ■ ;^i.©;., I O ar,/; i q 1o -Jt UTOl . ' I i 1 ^ ttT:, i ■*> *' . b . c».rr: « oi'u. r.i ':I'I ,1c ♦in-^ ,. - ..! X ^ w* X ^ -> ■ ^ V ^ d 29 into ^en crushed. This sometimes has considerable significance in the washing of the coal, particularly if the impurities consist chiefly of mineral deposits in the various types of fissures de- scribed, of if the cleat is such that the coal and the interbedded impurities break into particles of different sizes and different shapes. In some coals this tendency is sufficiently developed to make possible a measure of separation between clea.n coal and dirt- ier coal by screening out certain sizes. An example of this is shov/n in the following table giving the percentages of ash in vari- ous sizes of coal screened out of a sample of raw coal at an Eng- lish washery. 1 TABLE 2 Raw Coal Screen Analysis Size inches Per cent ash Size inches Per cent ash - 2i 16.01 1 “ i 10.03 2i - 2 16.42 i - T 15.41 2 - 1|- 11.97 t “ i 16.89 If - It 15.83 * i - 1/10 16.67 It - It 13.16 1/10 - 0 20.85 It 1 1 8.75 The structure of the coal bed and particularly the way in which the impurities are incorporated into the coal deposit has an important bearing on the washability of the coal. Most of the coarse, removable p#irticles of refuse in a raw coal, as crushed and prepared for washing, are the broken fragnents of interbedded or subsequently deposited sheets or veins of mineral matter, shale, limpurities in raw coal and their removal, - Drakeley, Coal Age, July 24, 1919. •a I It- • o.e... :l -ell :o/t«r o:fr? i '’82 ’ j iJ at p ij ' * * : . ’ . ’ • -J.t •?. JO Pin"' ■*■ 'oiJ': 5 -‘oo or ' ‘ -.. oi"r.:v ?rf.* •. i c)^iso'.a*r, oXJiaaoi y L. r:i ;i.t 1 -i’ t'ti^.|: -> V .X -A -i ic ' n 1 '.i ;=. '.t*!' > _• t 't . L' x<^’* ■• '*00 'i -» . :’:otoq :} -li' •. -. iol *rl' .i-- J,: I.’i-o "' •: 10 nf 'T^i; ' X.,‘.i'"'0 ’to ' ':;/c o t nlf! X.-f-A .‘-''■'rnH . -1 Td.iiJC ric* C-C'. ^ r ~ xV r _ J.o r* _ j I - X l-il ' ^ ’1-^'^ " . ’ C .t ;r;;i X.i'Ov v '■', * 'Tc 1117 Oiil* ,-^u ' ' ' '* ‘ - *-rr ‘ 4| • h.“. ' X i . X-100 90J “'J’rii i>(> j i-n j: '-yi-. r* ■? 1 ♦ .'loiiiv :i'-j .cuiJ ;o J.i.fa 'Ttv :iu ■ 7 iUttotrrf^ o .If . . 'j r. V a/uTC ■! . Xc aelot^i:^ yrlMTa^ . .oirxr .'o I).*':; •-'.X ,' ;v ; r.OiiO'Sd e . , iXtIli.v io*! . Uy. ■:x'- ..i I. i/fliov ;ro fto.; >tiO(js6 ^ | 30 1 slate or py]^te^^^ccurring in some of the above described crack's or fissures of the coal bed. general the impurities break irregularly into pieces of variouls sizes and shapes. The coal, while forming also many ir- regular particles of- all sizes down to the finest dust, has more of a tendency ^to separate along^ [^finite cleavage planes forming a larger proportion of cubes and prisms than the shale and slate with, as a rule, fewer flat pieces. ^ The first breaking up of the coal bed occurs during min- ing, primarily by separation along the principal bedding planes in- to horizontal benches'^ which at the same time break up into blocks or lumps by parting at the well defined vertical cleavage faces. This is', of course, accompanied by the formation of more or less dust and irregular broken sizes of coal. Then, in ©rushing preparatory to washing there is a cer- tain tendency , more pronounced in some coals than others, to separate along the minor bedding planes, the boundaries between the dull coal and the bri^t coal layers, and at the joint cracks perpendic- ular to the bedding. This Is not intended to advance the idea that coal breaks only along these definite lines, but there is a decided tendency, as described, and consequently the detail structure of the coal determines, in a measure, how the coal breaks and what is more important, whether the coal and the dirt break free from each 0 ther. If the impurities in the coal consist mainly of mineral deposits in these various cracks or fissures along vdiich the coal tends to separate, they will generally be exposed when .the coal is crushed, and the chances of a large proportion of the dirt parti- • i a • ■ ^ fi'iU'-M;- "iQ eaio« a. « &' -- ■TL '31 f . 10 Jn: XlT 'A -j-kJ 2 iJ 1*1 tfr j £a^p.T>:^- fll- . .: *^V 05< 4; fiiir'", . . 0 . .^rfiL^/x;Q ^dsjcb *lo .* ' 1 * w ..<*» i Ip- i i ipl y 1 J ' 1 ~ "7 't^Iu" 3 *. *, -i :' > r: M.2l ^ 0 j .^i* -) '/A .ir. I i'..; 2 et :■ _> lo.-f'j:' :. tioi^ioijol .r is^'! •> ■- ‘ *• - » ' - .: J .a*> -xc-r k . -n 4 : " 30 D ‘ : i ICO • . v' • r< ^ •'-'•»/ - ■*• 3ii: * * 4 Ox »> 0 ^ G •■ .Icj' 0 :,: , ; C'l) { :. tt z* r:e^ ak.j ,i-' t Xnonilo- cf » .'■ ■*.' - ^ f > :? .■'!.:o j 'lOY i C.M /fn - * Z>'.' •1„ :’0;j v:.? v/i : 5i ri.»;i;.3o:. o x^' , ■iuc/'o 'io , t ,•'. .*JT • .f ^00 -'aO nc*“"oi . x-.v'.-iniii t.L-w Xuj'vM. -*• ' • 'i ,1 n t A^’ - A ^ . ^ 4 . *» .’J , .tj.ii .... -.^ , i: -’o '.’••'i' ro.'>'”:o> ■•. • j •; cb.'iiyc-J a.\ , • • iCiiiifS e.w ;gnoI:?. 3 --^o i-' :-. 5 ioi, .^rii Ja a J)iu. Isou ■ •■•;-.>-■ i :i.‘J Vi'. P.T -i So; kI a;.ui' * .i.>i>wS oS z Uu , 'T . ■ r;i ‘rxD;'j :' , ' 5 . 5 1 £; ileij shsJ^ \;I;ro S3t«=^sii iv-oo !'.5 t*i , b e-i JK? ,: :»t> -Jigir' ':*.v b.i 9 ai.’.^zd ..u'O? 'mow , ■'ziia^z'ir li «i , Xapo \5. -- r.;e'xl ar-i‘i ?L:0-: ^ r'i - -b t- cj i»ns I/;oo o/j le 9t0fSi •» • ... A ' . ••■»J.p • ■ 'i 55 • ■'"-■•/ : ic- vl.'iiisi? ~rL‘ :;j. 3 rJtr iiiiqxtd btIS '-I ^ i<»0'2 Ti? rroir^t^ •’•..'ol ^©‘rv'ijsi'^ 'rn Cl/oil-.v iU " i>‘n; OfTX5 ‘of '/.f Xni'i.isi-i xxi;v? x^rif , j -rx • 7- -s ds < ^ 31 ■becoming cles^detached from the coal are favora'ble* In many cases the natu- ral cleavage is "between the coal and the dirt so that they break a- part easily and cleanly. On the other hand the coal and the dirt may stick fast together so that it is easier to make the fracture in the coal or in the dirt part than at the contact. This results in particles part clean coal and part dirt. Fortunately the latter condition is not as common as the former. A coal in which the im- purities generally stick fast to the coal in this manner is thereby rendered very difficult to wash. A coal,v^ich is principally debris or in which the laninae are very thin, is somewhat more difficult to wash than one containing a large proportion of bright coal. The dull coal breaks more irregularly and more finely than the bri^it coal, vsihich forms a comparatively large proportion of approximate cubes. In general the higher ash parts of the coal break into smaller particles than the cleaner coal. For this reason and be- cause of the large proportion of slirae formed from the clayey im- purities, the hipest percentage of ash is found in the fine coal or slime where it is the most difficult to remove. This is illus- trated in Table 2 , which shows that in the particular coal examined the material which passed through a l/lO inch screen contained twice as much ash as some of the coarser fractions, 5 * Chem i cal Forms of Impurities in Coal. As already pointed out in the introduction, the chief concern in washing a coal is in the removal of the sulfur and the ash forming minerals. The sulfur in coal occurs in three chemical forms, namely, in chemical combination with iron as the bisulfide, marcasite or pyrite (FeS2); as a calcium and sulfur compound gypsum ( caS04. 2H2Q) ; and as an organic compound in combination with the carbon of the -11? , ' B jr.r 'I 'C*Uvn . Ja'xov. \ n*is £Bt • zLli jl<;;'i* l>' ...^.ixi \;onr ijAt !,...• X.i;oo q 4^‘ .'tiSKwO^ a* : /■ - *>*■!•• • ■■■■;'- ^ r ',' *I ^ »■■'•.• li’ ?' ni *l ,- , J C-? ‘t‘:'u*C~OJ ii."'! HDi^a \*ff || w ■ " i' V-J.t/IOT ... . . > ,:^-w'J n-'r +.. r>^, .r .^o 341 ’,u^' ./ t£>." .*- .L 1 ^ r.L' '.Xov .''.i;j-i c'i ^ - J ’I -:.j ■ ;^.ipiii tsoo r-;iix& *?Taq i>i r . "XO' af fto -^0 0 ;cn ei .;oi.?ir>“" -> '• ^ ^ J - 'o* ■?«=•: • tain, -ac^ruroa ~..U I. .,v ... >^- \x ^rr ^ ^ '' ,£ '^5 3 A . "S^ it* UOl'i. ii.; i> UTC .';Dr!l.’ '.I ?5 .V-ifOX'* ..iliiiJ 9.H,-a.-I :. ‘ :"j /OXf^ r! -XO ■ *• -.‘■‘ti*--* ■• - qcX^*: Tciq •'■: '.-‘J • a ; .irrix v!:c'. »oo .-uBr(* r'r , •- * ^ ^ •■• ; ’•• V. ' tl TS ii.i.'; 9101ft fTr ■ •;- I.-ioo. .C‘>-A * •'■ * 5 AO iu:::..’_r-i ....•- 4 Bsr'Icl . :.v?' ,,u;oo Xj?cc :j .-i.? iu, _ i i/j t:., ad^ ,. A-r'nt;;-. /, ' ' ,??eo'iio n<-n«ei ■ rnJ t; ■ •• . * 0 *. ^-:.0 iiu.’ ix .-; -inxi j ^ t,.A ii A dfit Ji:ox^ L - - •::-ir*, i .) ..oi.f tr^c-v * . a;*!::! 9r:s to ^ttu^ * :-u: t».:i i . nix, , j .:. „^iri c,;r . - *;i:x Ai 3i,:^ */ 3. itXuo.i. t . Jj j 2 iii 9 , .’ gj olor ?rxiX» ‘i (C *''-^-’•. 7 :^ I :o:. -i .. 'lO.* nt .t .. • * , e^-orfu ito r • . -9.!:X£T ..i ■•■ -. . .’rc'O r.'j^'ton ^ oi'ii C'l\l a ^ofieA3g lirv^, ' , ■’oi. ' 'r V laDiiJOy fiii* '* ■ \::o€i h^'‘' ■' rJoi/aft.n:. ooi^-^ ' ^' '' ^ *A -’ -'A Ix£ ' ;^ x_0 £ H i.;-x:’-ae- -re 'l^irto lo ,X*T'. ;■ " :■ • *.3 r. r ^ i ■ .-■ f -L - :'l r-ri vx;.. r,,(,o •£;'XI‘./.n />nT . ^ *'' *• -,J. 5^ .».x:3-r3i:r , *XIyfl2rf 'c-fi «u-a. .♦Xvt KoijA’,.,io/i..o X/.ol.v.^rio ai t - * ^ iOxp.7;;c,o •xr.xX...’A; - : ’i.'loX^^o . .^ i) Zi X-X'^fT » - t"’ o; - tc r'.t..i\^.’j -z^.j ^ x?r noX^isi"?, Jcco «£ bnssciiaoo uiu»S7v- qb ' * «« » i i *> i iii XiSl 32 coal* In addition to these forms some coals may contain minute quantities of free sulfur, but this is exceptional* The pyrite and gypsum also contribute to the formation of the ash remaining after the coal is burned* The greater part of the ash, however, is derived from the earthy minerals, clay, shale, or slate, which were deposited as mud or silt in the swamp with the vegetable matter which formed the coal. These vary in composition in different seams and different localities in the seam* The soft fire-clay deposits are usually a comparatively pure clay, consist- ing of Kaolin ( AI2O3. 2Si02* 2H2O) and a little fine quartz sand* The shales and slates are similar, but with varying amounts of other substances such as the oxides of iron, manganese, calcium and magnesium intermixed. The layers of shale or slate occurring as partings between benches of the coal generally, thou^ not always, contain some carbon which gives them a dark color* The black shales, which contain a large proportion of carbon, are commonly called carbonaceous shales* The other ash forming constitutes of coal are the resid- ual mineral matter or ash from the original plants which formed tine coal; and calcite, the carbonate of calcium (caCOs). Some other impurities which are not of direct interest in connection with coal washing are moisture, oxygen, phosphorus, and in some coals, small percentages of alkaline salts. The moisture in coal is of course increased rather than decreased by the washing process* The phosphorus content may be reduced somewhat as it is ordinarily associated in some way with the mineral matter or at least it remains with the ash after burning* The phosphorus con- tent of a coal is a serious consideration if it is to be used for T* 1 f ‘ :(• 1 '0 ^ H -y. ■ . «.,v. ih fioiitv' • 2 'v; ~v. u o . } - li ■5, X 'f;'. ."^wi .1 >'rf i . , U . M ) ■c: - . C.'KIli , O' 'i- •:u nji? ■,:; LCT ' ■ \ .■ . :) ®aior ..i «1 J. „ ., ‘J . f ^ 35 metallurgical coke. Where soluble alkaline salts occur they may he removed in part hy washing. Salty coals are evidently not common in America, as no mention of salts in coal has been met with in the American literature on the subject. This must be a common impurity in English coals, however, W. A. Bone says on this subject, "Some coals, besides containing insoluble mineral matter, are impregnated with minute quantities of soluble salts, principally the chlorides of sodium potassium and magnesium and are thus called salty coals". Physica l Forms of Impurities in Coal. In the problem of efficiently cleaning a coal the physical form in which the im- purity occurs has a much more important bearing than its chemical composition. As has already been pointed out the extent to which a coal can be improved by washing depends very largely upon the structure of the coal .'uid the way in vdiich the impurities are incor- porated into the coal deposit. For practical purposes in a study of coal washing methods, the impurities in coal may be classified as regards physical form, into two groups. First, finely divided impurities structurally a part of the coal and inseparably mixed with it; and second, coarser segregated impurities, which may be separated from the coal by | mechanical means . ^ IMPURITIES STRUCTURALLY A PART OF THE COAL Impurities of this type are not separated by washing from the coal substance with which they are intimately mixed. The ad- “? vantages of a knowledge of these constituents of a coal are all negative. The chief value of their quantitative determination is that they fix a minimum ash and sulfur content of the cleanest por- tion of the raw coal, which is generally called the true, fixed, o'j Jo-- \;I'v^adbrvv> •- ..' 'i 1 *',’ * 0 ’. Li- :'. i :. i vj-i'' fv'i i'.osrjsLvo *#aj-**; e:.i 1 3 ii;rc'’ , '31 Tv:' *tv sv. 5 «J :s.iie 1.-V ::ci/ m .■:ijp, ■oti^ f:‘j n-£ i/;. ,;>.':lrTi 4 * 4 flOO , c£i;o; - o:i .-■r/X- j . • • -. 1:1 Inuii/p .•'!•. vlfn. r^v .1 • .' 7 ; S« 9 i - L.: '.rO* X ■ J. , UOl- )r; • . ..‘ 1 . 1 1 : 1 ^ ‘/SCI*. 3 j. 1 • 0 • * k . ;r\ . , ', ■ ■ Lai-t, : ; ’ :. : •^ ...: r.i)/oi': :■ ^0 ^ oL#:l 7 .’l •' ■ ’ . 0 .:' *.• ■’ . w ; . • ... r*ivoi 4 '”' * vli*i,';: r-.i '''^T ' : J 7 . j z.'* :. .. •* *.'i on li_ : . V.-O i 'J ' 'll A . c?iKOv :■' "j rc-n; V C . 7 . V'l :> . ..-J-If):* '.-*' .'■> o\ V -i ^l^J: . (.'.o X.Jou ' i or.’. -« i . emit ■ ./'jj.-TT .rl \' ,.v 5 * iv X ioi ’’ ./■lb , - v~., - ’ i ii V- 0 ^ j.'.;, oltil *:.... I ‘ t * , . : i :£fi ▼ leOc 'so x,'^u.' .. 1 - . 0 i J’' o ' r: .’7 : o 't V-‘. io f: .. . 0 .^ -u r *!:• ft f 1^:42 f ir^r^ riX ‘ T" jn:i . >r ■x:.~»r.L"x.-^a .tiiri-. 'i^xcii i-- i « '£X ^ . t ^ : - i'-i ' i’o-im '-.eiU Jbft:* er« 'to V’ ^ L--: J 3-ssriiik og \i' Jb , c \ J:j liu^rL-z Jvj i joijxo'rfooi’: JA.00 ai: 7 10 T^iAT A VXiivXUT’JlJH? : -ii!lTXH J'C4£l » A , . : : V' xi br ; • -■' ■ -i XX li " I ,; 0 0 « 1 j fipji , . X .? '-• i (1 ? ?: ' ..«' ctrf('?.';io:. 'ti.l.lb, - i '' j ■ ., I '"O V 1 ... -j X ? r;, •; uiiO? '0 ajl'; *■’•' r •' r'- j Aiiluv .1X7 OOf?. oasrfl; '!<' 9 r-- -. •**OilK *;V-lT ?;rr--v 'l:>l-.'^'o ♦ ' M ♦ ,i,KA TTf-r-^t ■ .r :-ri'i: !i ri'j.’ . , v.'-*.c ftjfi. to r - i Vi 34 normal or inherent ash and sulfur of the coal. In the washing pro- cess for reducing the percentage of impurity these values for in- herent ash and sulfur may he approached as a limiting minimum. fine disseminated grains of pyrite, finely divided clay, and the mineral matter of the original plants. An approxiroate determina- tion of the inherent impurities is often made hy crushing the coal to one-half inch or one quarter inch size and immersing it in a heavy solution which will float the coal hut allow the heavier min- erals to sink. Analysis of the fLcat product then give an indica- tion of the percentages of inseparable ash and sulfur in the coal. Some writers have erroneously designated the sulfur determined in this way as the organic sulfur content. Powell and Parrl have de- veloped accurate methods for determining quantitatively the differ- ent forms of sulfur in coal and their work has made it possible to determine the percentage of organic sulfur. This is of great value in examining a coal to determine its washahility as a careful sam- pling and analysis suffices to determine the natural limit of sul- fur reduction which cannot possibly be exceeded by a practicable method of mechanical separation. It is conceivable that this mi^t save costly mistakes in the design and erection of plants for wash- ing non-washable coal# It appears that the organic sulfur is united with two different types of coal constituent, and is classified as humus or- ‘ r ■ ganic sulfur perhaps more properly merely asf Phenol The common impurities of this group are organic sulfur soluble sulfur. ^University of Illinois Eng. Exp. Sta. Bull. Ill . . A ■ ^ *'■' * -- hr . , ^ r I I.i ^•.. X»wat#a ■*. t ‘ioj. xS L’’i.iq:'\^. ’Iv {^,*j .i'.."^o':v ? !il^ NiTiy. %ii»o , c. .. lar..-; ^'’Tcfq o- *• > • V , , ,.. .M o.‘ y. 7 ; £in>; t ’.■ o ’. ,1 6ft^ ' ; , Sk yii"? > y,.i > • ^ ^ ^ 3 -iv '!• *: - i 'rr.t;:! .Xir J -■ Cf^ : ; • fji , -.71 Oii^' .. Ic' ;7 le.ro v:'X • -i.'-i 'C ' ■ •.. .;oJ‘io Hi o I'z. l Xr:j S'i 'fo nox.t .:/. J. 7 )£ti •'>,, 1 ..': : I, . ;; • '(--x *i‘J ., ;;, •>;.'> ',7., .no.'ti ‘Hxia-.>Ai'7 . i. • .1 jc .r c'o -V .iT^XCi- ' .’iuiilv ^irjsy- •*y .-' :■ .i' X v.* '. •.. , £#i:r\ ■> .♦..'xo R^rYr^*V , oj. ."5T.:r,' . i. J- rl T.ull'' hi.' tc-k- ; I; ir yo-’^i-TJ-noc'T'j .. j.;? *>0 ltd.? % * >iZ • j t ri ■ ' V ,. :3’-J .'".1 ,j . .'o^ •yj-x •'’ t, \zt.: i'V^ nmoS • •.' 'f -*:••:’>. v; . j.j, . 7 ' .J ' . £>* :oy, -i»ij r. t.'i ;ji. 7 ,j. - i j., r •-ei.il!> v'.rvl^* . ,^-.f \ ; i flrrj . •' ’lo a -'id J.i*» ■-■- •' -■- •• •, i.r JuaTio j » j ,-57Mr> I,j''v': •••. :■; C-'. \ yji ',.'rt 1 1 ■-! I :jo 1 . j.i: j ,: .'.^y £il - d wj;..l7 : .*£.i..- j.-,r > .i.rxe'Vw.'f OJ i7r3 -;\;L*i.x. , J.i?; 'M“7r-yl:fo i-r? r- a>' ;c>;.:! 'rj .roifiV xxoi.?oi/o\r , -y anco -iX JC3 : . .. f . 7 * • ’ ^ *" ' • - r;-7 \u.'^.'ior vl’X jqo'i T s’locx a*i.a'*ioq 'I o i' " • c . . -■ .p- . . . yXoX'Ico . r ( p Knit ► j..' X i o '■'* f ^»*t -"'V -I. nL’-^ 35 The microscopic pyrite^ in coal consists of minute parti- cles rou^ly globular in shape varying in diameter from a few microns to a hundred microns. The proportion of the total sulfur that is in organic combination varies widely in different coals^ althou^ in any given coal the organic sulfur is much more uniformly distributed through the coal substance than is the pyritic sulfur. ^ The organic sulfur of some coals is sufficiently hi^ to limit seriously the extent to which these coals can be cleaned of sulfur by washing. As a result no doubt of the deposition of fine sediinent in the coal forming swamps, contemporaenously with the accumulation of vegetable matter, coal contains more or less fine clayey mater- ial distributed all throu^ it. Dr, Reinhardt Thiessen^, micro- scopist of the Bureau of Mines, says that microscopic examination shows all bituminous coal to contain very fine ash particles proba- bly colloidal in size. Plant accumulations deposited in still clear water would presumably form coal containing none of the in- grained clayey ash, but only the mineral matter of the plants them- selves. Other layers of the bed, however, which may have been de- posited during a period when conditions in the swamp were different and slimy mud became mixed with the organic raa,tter, contain varying proportions of clay. ^Theissen; Occurrence and origin of finely disseminated sulfur compounds in coal A I M E Bull, 153, Sept. 1919, Iwasaki; A Fundamental Study of Japanese Coals, Technical Report No, 2, Tohoku Imperial University, ^Dis tribution of the forms of Sulfur in the coal bed, Yancy & Fraser, ^Personal communication. - V ..i ; I- :,x ^ r>iQOOQc-C', { r; .>ftt /* ; wi I-*', . i : IxTir-. t*..: ' •'H'xii-i. ol;r, e.ol' , od .' , • fa'i 'J ■ ..'u: * ic r.ci Ji c- r.-iT ' . J rvri% :u f .*■ : i':? ni j ^ -.QL'ot i)--’ i/Ji- . '-iZ'Uci.tJ r : e.:; :' 0 i t 5 »i oi'/iij: ' 5 UTftOo 'ii;':Ik;o '• ' . ''If' ai^* Itv- .• .,* •;•; rr.ifiS fr. v. i^GO c4 J . ; " "/. r<-z!i^Lf,c , zr.x ‘ i' : t.! o£a : i. ; . . 'rlflA. ’•■ I'-'' 1 -ia '.■’fi.jftra O'^ vf«»o ai • .•*■ . -lol/tw f ■•• t' -|J io J-QiJO > ; r j 'jha : L: MO ' :■ OrJ Twii ' jJL>i .-.i .X. d3 ■ ' A ■<- ' V ^ ^ » ^ . c- ' ‘ ~ .:i’l s* . J r.^L iJi. , ’’.i \. r. i .1 o'-ri "‘.U-'oauo*: Xlx:. q\ ' ‘ , if.-: v^S* ij 1- : J I'i. - v'.; '■ wl .O ’CU UJ 1 .00 XI vj. * • k-# ^ ‘ ^ ^ I . ' 0 W jS .'i — % - j >.:; I.; ^.*:oA . I 'Jiv,:. cacl •';I i..r X. ^-XiSXX Oo V -i- »- j j! '.(T X'XOl. v I'-'O C> 7r 'Id-.ili/ »{ • ' ' *W i| . ; 1 •)I:‘ I. '1: ; 'J "> . <; M ' ^ ; O '. "I'-v I vow V , .►A • JCS.U X> 9 nJtiiT:: _|fj -.to ■ 'TOi'.rO ,ct>vXoa'^S I ,'j ' It?-';'':';! ' i^r*. r. vaJ.iJi L.;;oii a- ‘.' xao ..•a;'-- O'OA'.f'q c ^;;:X'i;if: IjiiJ’-.u vC i •,;! V -;i;c^^ao^' ■: 0 ^ c.'f^ .U It: ©uijt-oori •^r-I T Lj 1 . aaox j“ip{jc*t : I'}it<’ i;...; a •• lai/^oO ;.:©jfccufO X r:'-. * r; ( ..'‘tiuk ic ■• X. • :n'i ?,fOli/sixiari t“5^ .XT '*. 11;; • •>.'^1 .'>r*.yc :' , 5 , - - . rrJ:' b 8 .tl9-v ’, 'i V rt\. 3"neo'xr^' 3f . : i.^xtos « riT]' Y ^sjt ' »\ • '!.- 't* .*n>' .: ■;. :)X.- •: .. \.a* .; » * , , i: ..: ~X ' -ao^ ■) ' * .♦^‘■•■'X ' £aac *>jt . O'j ;v.-elo r ■?, 02•x^^ , . X .) . ' V . ‘ •XjX joo "c*' V i ^ cX ci / . v . t uv - '1 on ." . ' J V - . ^ G.,ej[ ' '1-^0 • 'Jo *m< ■. *iX Lie, ■ ,1 i ■• '■'.ij. • X-jOw . ' c II- ' VI; 3 4 9.r j-iv-,... ,; to ; ^ *';£ .'O/jsj 'X 0- ' c>_~i \ O'- ^ --i */yi— A «; jL 1 00 a 'wiiw ^ • ** k J G 0 X t i : v.i ^ ’ Xi ';'• v'l U..-T I . 0 X 1 r::2.i\' r.l vrix *.■ X . 3->cU . 1^0 0 < ^ ' a ■ x: ‘ic ;s:*2 .; -iai ooJlr*Qq-:^ d~-' f/ysD. ^ b‘44v Ol i C i Cj .*T i.-:.f 0 01 IX. xic'iX ■ GaoT’-' XT... ill •e;:.; > '<• r * .- » ' «► s»v* ^ * 1* . — r .j-s;a© v Sjug" ‘iJ u ax, Xi h: ■ > , .* = 1 >-■ ;; X -10 ototi'-'- vss'iX:-s cnco nc . Cit j;ri' .', o,J- jof I ■: G o-v X cuk’xK' a- rfp^i/fe saX- • ->-3^ - * ii: p-ol.ifiiii- yi: o.^ dv,v cio'JiH ooi rXx.XncG •.'•'pi:f'y Rni .vs .'t X .\i \^oIg i . 0,'L .... svaulG.. rtoi,' , '.is, ijf 1 1 •...•; ■ »itX«y r .i bO-o oa ol on - • it i«V<5jj,U 1 o ori.' ciuo':.. '.'.oax o . . * . .1 j-nX"! aioifil'i xo :.. ~ 37 natural dividing line between dull coal and bone coal or between bone coal and carbonaceous shale. Probably the most satisfactory arbitrary classification would be to designate coal of the debris structure, which is clean enou^ to include in the first class sal- able coal, say up to 12 per cent ash, as dull coal. Coal, which is too hi^ in ash to include in the regular marketed grade of coal and yet too good to throw away, mi^t be classed as bone coal, and that which is dirty enou^ to be discarded without question may be designated as carbonaceous shale. The all important characteristic of this series of impurities is that the ash is very finely divided and inseparably mixed with the combustible material. This is well shown by the results of some cleaning tests made on the Pond Creek coal mentioned above using the Trent process of oil coagulation. This process consists essentially in grinding the coal in water to about 200 mesh size and then agitating y/ith half as much by weight of crude oil as coal until the oil and coal coagulate in a semi- solid mass rejecting the water, yihich carries in suspension the free detached earthy particles of the coal. Tests on the Pond Creek coal, which was of the boney type, gave almost completely negative results, the water which separated out on several washings of the same sample carrying altogether less than one per cent of the total ash in the coal. This would indi- cate that even when almost all the coal is crushed to minus 200 mesh size the ash particles are still included in or attaclied to particles of coal. The other important source of inherent ash in coal is the mineral matter in the original plants. Wood in its normal state contains on an average about one per cent ash; but since the plant - P. ;?■ - -I J\-. :\ ;•»- .' ♦ vO;:jD;5.n . v.’o blu^ '‘i - .' ^noii ^ , St ::;. .:- •- .■.• ‘^o I:iCO 9- ^i^.^ la : I-j -.i ’ ” < *•:.•. I c:i Ciu: - , ~-0 . ' a , .-■ •r~'' , . ; a. -■ilt ill a^I^Loat qS lf^*=r> f.I ’^1'; \ •■•-r .. i , r. . v:b\r!.) OJ .cjO*J ^o3 ‘ • \ av , x i j - i*' bfib vJ c^'.J . zrj^.} LIji OtC. . ir'^'^iiciojynad'ij-o */ / . oy.Ti.ri:-> r ,/i -*'■<- ui :fr ; ^ r- .> .i'j.y. i 1o 9l'>! i ■■ 'yr. il'-r r'x .:;i?':'. . i.>'} Xiv a.'1#r:p: > of)xii.i v.::>a •q.'i'r.l : ':-.j ,:t/- ;p:\ CijOO 1l i? *'^ * tIj u :jT' ;oo £i c ic.*»o')o-> TtV 9 : i><:i j ••v ir-, Jboccoi.’rtyy: |,.c At r;j: i’.o ' -‘ 3.:':.'>;ii^ ni v:i ,£> a^elano.". ■ 33*»ootq oii.ij >ji 'J t'i’. .T i!- • -c A ^.J , i ,. .. .^ VJ '■ IX a>. . : 1 . : ■ .if;-?. ..s:is rqT ri v'yi -f/Cu. .'.-'.ru/ bn- XJfc.-: JLi : ^ ^ .X. t bi/ID iC ...J ltd :ri c j.i i'L j ;{>.j.l . , • -i.j’ f ;-v. j , • -:'b3*i ®s*.>u bilv*;. . . yr> or:^ e'.AC i* ri.-:; v. J* ,^cr ■ -V..’ *!.-• «._.v / , ' ro‘; 3-* '•. :> u?'*?'? ,.' u- , . ;c>r»a xoJs?.- ©i,.. t - yrirqjyc v. tjJ y.r, ; '•. o -.'’V:';, •;3al ■: ?•'-■ fl., o.i qtr ■ n a- vra ri:".> » uo Jjo -■ '-•■• axf^" . soo a:I.J rti xlei* XrJw-‘ '».:j ;; X.ijp .}';o rt/AvX ,-f CCS a'';:Js3 i*S'iPti;3:o «i i o. ocii .tnt/'iXs nc--. -' n.'VT jjjuj. ao •: -.• . 1 . .r. 3ti ji oin: I ! i ^ - jy . ■: C : 3 i ..* 12L i\€\S‘. J • -9. It i s Jf’jyis , oo lo a' riiXxc.q fl.'b X i- iU:.> .' y 0 r ‘J 0 1: ♦C- T ''.rf '-.: ..X.. .li. boo^ 1.3 X AX’!.! 'J X v'vi ; :>. x.vi'X s^iTo 38 remains, in the process of coalif ication, are subject to great loss- es of organic matter, without a proportionate loss in the mineral part, the ash from this source in the coal may amount to a much larger percentage than in the original vegetable matter. The total inherent ash, of all these forms, varies widely in different coals. The Pond Creek coal, already cited containing 34 per cent ash, is probably a sample of about the maximum which would be designated commercially as coal. Some of the eastern coals probably contain as low as 2 ^ per cent of inherent ash, and small fractions which contained less than this have been separated out of coal samples by floating on solutions of 1,20 or 1,25 spe- cific gravity^, SEGREGATED IMPURITIES This group will be considered as including all bodies of impurity which are physically distinct and separate from the coal substance. Carbonaceous shale deposits belong to this category, but because of its relation to the other substances, dull coal and bone coal in the series of clay-coal mixtures, it was described with them, A particle of carbonaceous shale may be considered in its entirety as an impurity since it has no fuel value and is es- sentially a shale, containing, incidentally as an impurity, some carbon. The principal impurities which occur in coal as separate, distinct bodies are shale, clay, pyrite or marcasite, calcite and gypsum. Broadly speaking, they occur in the raw coal in one of ^The Distribution of Mineral Matter in Goal,- R, Lessing, Colliery Guardian, Jan, 28, 1921, }^ »< , • V. 1 ' . i .i/iaciT i ' .i ii; aooX o:^ ;.;d u^-io :! ■I'l ^ :c^-* , ‘Jii-; .>ir.‘'.af . o c ■ . ikOiK ^ c:' rri. -'-• . X300 .:i ^o'.u-o : * :'t ria< o. ..* , f . . " % j J 'viT •-•* i ; 3 g V ' ' ' X r, . . J :. ] t * '• '' ■ , - • • • :>o ^•’.'' ; .V. • . J. j _ _ ‘'>'1’. , q' t C- - J.'O'iii io eli; “c. & ;Xc'rq 8 , Ififci v>f. 18 'I , j : •*.' . rt'V*' nw ■,.:'i'^ . > *cw±#^-?K' ••T.u *,nX3jtfS_ : v,X f-'rfn ^ 'i? . J’:?c .CtiOO a:i \;J i .•.•'t- i biuo^ ■ 3T *.*:f'f! iiC: ar wcl Ui. r ii^.i v.' I -■- o^lii'lU-i-wX 'jaLTAC;«:’XL<"3 ^ S Lb 5 oii n.j t •>'- st. •’ oo £ ' ILin *Wi.-TC-> ^irfi' * - ?)f:^ /cni; "•iw vI.' -jc T"*! t ♦ XoO ;■; •:»'i..'';»' i3 i. jr. : ''£> mXa ?;■ ;; v : •:• .,:o JnC . J r ii ! 3 f - ' • ' :vv Lltj') , .. 1 . i • •, ■•riJ 03 »3X ,-.Bw«aod t.U'^ bv •"'i': . io: ' » -a*? , - v'l.--' ? ? Jt^ .’. ‘lo g. J ;:i Xi;C»a onJb ■ ■' "■ /I o ‘ J«0804»nuuifi0 Iv gIo^iJ*rr^. a ‘ ’ ..I . •. : ;s L- v j'l c. c.i^J -^3 i't ifq.it i **-i j; ’i3or*i..';i0 e ;.. , ‘ • L .:: :i \ vi.C i^naX ^ g:_ : , «iir.i.<3;. ,Gi^r(g rj ■ - . - ' ,. . -gr ,1 ■.'■ ••' " •••> i 'C'/ n; 7Uipr .'-.i X6q!?nl*r' ' ." ■' ■ -i >•; ni. liioo •■’ij'-:. '>o3 qi i»/g.oc vp^:’ ■ ci^i . Jtjiri;; ,H - 1 : 3 .- 1.-: . ■ 11 . ; ' .toi 3 •— ^ rs*.\. , g^•rTr.r{^ 39 three physical forms, namely, as layers deposited "between the tench- es of coal in the "bed, as infiltrations deposited in crevices in the bed subsequent to its formation, or as extraneous impurities, usually from the roof or floor, introduced during mining. Shale generally occurs as layers interbedded with the coal. Pyrite also occurs in this form. In the Illinois No. 6 coal a continuous sheet of mineral matter called the blue band is usual- ly shale; but in some places it is pyrite, and in other places shale and pyrite mixed. These layers appear in a vertical face of coal in the mine as continuous horizontal bands and for this rea- son they are called shale or pyrite bands. Those which separate easily from the coal are called partings and those which stick fast to the coal are usually called binders althou^ the two terms are often used indiscriminately. The bands vary in thickness from al- most nothing up to a sufficient thickness to divide the coal into two separate beds. Those which are as much as half an inch in thickness are partially removed by the miner if they are firm enough to withstand shattering during mining. The thinner bands and small fragments of the larger bands are mixed too thoroughly throu^ the broken coal to be removed by hand. The washability of the coal depends in a large measure on the physical characteris- tics of the shale bands. Where most of the ash of the coal is in the form of numerous thin and friable layers of shale washing is difficult# Some of the shales occurring interbedded with coal have the property of disintegrating rapidly in water to form a soft mud. This also causes great difficulty. The infiltrations are usually pyrite, calcite or gypsum. This is the typical form for the latter two m.inerals and probably v -* : .‘sout 1 fc aco*'- Ciioy.^-f * , ' I , ' ■ z. t , I nr .'1 i-iti" ir;. 4-b onoi".t oiw XiTn ? ■; , jcJ ni^i-oo ;> t’c ^ Si-, -nx'.;?-.-.:, ^ 9c"r , tuX^v.*io i'jo*: ■ •'. xlX/ti;*!; yr r.iyouv vXX:*,i5ev'i elfixifo . . rXitv’ ;ti a__;:oo o~r- -'iitv. . ‘ iV 5:*0 : ■ t* ~ UiT A ^ _ X ' ■ .t i> I 'Ik/ Ua >.. c: -> 0 -I'J . .. (T '. •'.'i'53 i -‘(.M ;oXi»ii;i \;X X -i ix-? - • '-.i " >?u.^K «-^Env-5i , ■ J -:!r, z^My,y^q bn-j oI*;ris ' :iAk.-»rf *ii.i ‘t..': j. X w* "f i*Ti X.oo j ^ no a if a. ■X ■■'i c oi i v OK If .X *.r-r* V io - ' J N. Xr.^ci ?'C -• '’ ; . •' ' i .:-w enoi"' . .') . ; ' 1 ■; : r » 0 X’ XiilOO [i c.Ti't,*',.: .■ •' s If r.t ■ 9 IX • \Z.l. •;'»j ■'’•••' ,•■■: / «l '.^j;' ariT ^ nOw'l' Mw"*'!' r ■.■!'• 0 '’j c,J ■ fli ;■'.■■•.') i ! iiOi Ol t"t 'v3 ,* c;; •’:' Xoc.;' 'i i-’‘-JiTi •• lf.^rf • ;'Crjii ,r. m;a,. :l-Xi'1i' S30?fr'' -.-j:?,.: ' ii..qD« it-' i‘ 1 mjI-' 'U r.'r.Xu e*.'J I'lntix. X 'ir'y •> -x.^ sr.rtoX . .‘i i.A' t>it£^6d^i ' oj V‘Ti5- o.iJ CO.; /jsxiri t m 1 . t> rW lo t>:^ ".: r.rr;: •.;.: i f. X X-^vi^i-'W yS 'itJVOai'T t»J Oi Xi*0;j .'i'XAO'Xj ''oHX i^uc'znt ~ TZ-.J-oj':.- jc X30ii:y4,7 ^r-’J no dtu’?jt: 03*. ftc'rt=X •' aX a >ne:i ’ ' X..co onJ i.u :. I X ■•;•:, "lo risa *ds X-, ioc.'yj ::‘i.Oi 'V aln.,. yA: lo 80iX 5nX^jS£-' ::X ::fj ’Xo -. c “•;.*£ X)iXr3 r:X-TX XjoO'i-' is,4a- lo art j”: I j.i 7,ii.i.-ii'v/.voo a^X^.sia on.oe. ,,X^'oiTti^ ' a Jjjtt ; ’'to -:X-. ;. ' Xv .■‘‘•iX o*V..l * ■ • -■ ' . X, -'• . •j'voXi ti^) nji^D oalo •': -‘C -X ’ , 5'i‘£v;cr •^II jsjx.'rxj 91.8, ■'inoi J I i’ini o/fT /^v' XJ . . .*z,^ ..i; ; -lA 'C ' I' a^v T"I I'Cr- : r. .‘,: /.;X si ^‘i'-rn *! [I 40 the commonest method of occurrence of pyrite. The calcite and gypsum occur in the form of thin flakes in the Joint cracks and on the minor "bedding faces of the coal and in very thin veinlets which sometimes give a lump of coal a crosshatched appearance. These flakes and veinlets are very noticeable because of their white col- or. Since they occur in very thin brittle sheets they break up very finely and are for that reason rather difficult to wash out. Pyrite also occurs as similar thin flakes or even thinner than the calcite, as it sometimes occurs as a mere film like a coat of paint on a natural cleavage surface of the coal. This form of pyrite is often referred to as flake sulfur or float sulfur. It is very common in the Niiinber 6 coal in Southern Illinois, and for that reason the hi^ sulfur coal from this seam is considered an espe- cially difficult coal to wash. It should be pointed out, however, that a very small percentage of sulfur in this form gives the ap- pearance of a. large quantity. Bodies of pyrite in a great variety of shapes^ are found deposited in coal beds, or in the rcof or floor. The principal forms with their common names are: 1. Rounded masses called nodules or balls. These vary in size from a fraction of an inch up to several feet in diameter. The larger balls are usually in the roof pro- truding down into the coal. The smaller ones called nodules may be completely imbedded in the coal or in clay or shale partings in the bed. 2. Lenses, round or oval in plan and lenticular in section varying in size up to tv/o or three feet thick and several hundred feet in greatest lateral dimension. The com- monest size in Illinois coals is probably about one and a half or two inches thick by a foot across. They are some- ^Distribution of the Porms of Sulfur in the Coal Bed, - Yancey and Fraser. ■ '.' '■ -• !>»;•.. :■? C' •' jinoh ?rj I'l, {f'joo .,i- S:u' f ,’1, N’t: 'i- ' .•.:■?■?->••'>. i,ni' : ...iX.TacL* 1 '■ ■:w\_..-'oo‘': ' r- I? oo ho (fnu/I y tX’' l; * 3 !’/ ’’-:o 02 I'Ou '^.=. .> .92 i 7 n't \X'^OV f' -'a .. fj.T' . ;7 yv*N». ., -J: . •: ■ '. 'lov ni *: fDoo <“"*1.. , . .. . r t -.j,- y vlfl, S .T' \ ti 't'J iliiU i r -• y.i'jOv ;.. . ■ o* I'T*.'’! . . j-uyp ^ ’-Ji 'i^ Tlrft . * * O ^ X. r ♦ •rc'l • ■ y 9 TVQDC Jl ^ ..J , ACoi* ■ ■ ; ;-/->^3Xv' - n;:' tV V . j(j. 1. , * OJ t©tf9'le*i u--;i5o r. i f' Hi I qS i .Cv. 'if-'Ji'jtrTI *uJ /u fio/.taoo ^i'^■’V ji AL .'JC .’ ’' + y . •v.l - s. J ^cv ^ 1 '1 -• M rc' ft i X lr::i i:.:? 1*; oj x,.j. tir> . 7 i:7'0",C LL.',t&& 1 - X » <1 .». i , 1 -* i - ^ ■ CO- 0 0 i.-;-, ‘^edo'JU^e i L ;*^v ‘ . :i‘:^q Ic- *»f, .tJ03 la;//.. 0 , * ■* . • 'I :ooi t> . y ill It ( • ' Xac; ni X>oJi©o',, ■- ao.; a 01 ;.“.Q'.;' nio^r.i a'J i , c '^'ro • - • - « ■ -^yJ 10 «3 si nib on .05 U ■■ * ’• '(£, ' y ■ ' ■ . . -; ■ TT , - , , * W ■; 11 rf • i . -i '' ..'uiJoa'ii ,*. all ^IJ ”* '.'1 '1. L 'l -r'.J ni 1^1 1 ./m n 3‘£ ' ■ f 'r‘.)>i/C'l' £.'" on o ■ ' I.:d""co. "» - > »a ^ f ■ T ' • ♦ vJss. ; ■ ** - oiif ni HI. .li tiBff «• * / n i}o^a y _ 'j’i Isa'^vsf^ V - *.Ws- *. . 'J 4. U PkK^ i * ' H- ; 'o ur{;!t ‘ . •■ .^r .uo •''; i x >.; Si ?o oirua ,; -«* ^ .-.»r -.‘ 1 c.Q'j.J.i ill \i-.Sc: 3 .’J v.iij^vo' 3 ;>ony' yX *io ^::iX 9 V 0 rCj «ruI - : ;. *> ' • . "r ' ■-- • ., *._' • ‘‘00 -niS . o;': .>..* cal j o't 5 -jt’oo'i J&rt-. » C-gac ' '“•.e 3.9. v - ; ..:.;co o .: oiri. inti a /.:e/ 0 i 3 ...i ^/T /V;; .>*1 dftt :01c XnO: .I-'-o.-! _'. r:jf>., .v 3 G/i.-^ , ‘J.uat / ,. '':oi’* j ;;i \^Ze'jx 4 mxir. r oozii'ja «..>x -r j 7- ®r-'::' X. b.fi.CB .‘X,oX%'^vo “TiTc :5 -;.>Xli lo tOO*I -, G xil - , . :. ^ <*»; ..■f.ottf jca .tJOoi) '■' ’ r.oooiq j.T '. :,nX*n:rXc;' ooj - i;.i8 ai, uoi.rftr , <3-:. ip. '< j.XoT qtr X>.r Jr . •t'-jo-.i aX..,r:.# * ' ••co Cifi ' o5ni t> :S 'jS O’! ,;!? O'.tx’R . :o v£L'!if;.’’j t j oJ - ’■ ■- ' 'rj. Scdox . ,0 » ■+ 4U / 00 vi.: f^.,-' 0 o.?! • . « / -',. X ;j j :it.' 0 'i Z-’,t >0 jrUt i k, \Xixjui;' oO * 00*0X01 V.'; '.j^ J/jO'C,- ..X . ,..i» u Jo*i ;o -X> '.oi.l ai S'lib uX^^rtiiiriX o cJ p...? -i.Tt late*'! iO ‘j- T'C'Ct X*‘Xo fJIT J .^rij aoXor. ^/iiiOOflf' ,-ooX'i orf> X--ol’'':'ij .“a 4.;. a o.Xj 'io ,r.-,v >a.i :: X S'. 4. on On-,. fL- xw; ',*j^Xo r-nXlRVOuX: oi iir: ,« V J 9*/ om»>',£ 0 J i S 'luq.zL vO-0T 43 CHAPTER III FUNDAMENTAL PRINCIPLES OF COAL WASHING 7. Effec t of Differences in Specific Gravity * It has al- ready been pointed out in the introduction that the commonly used methods of washing coal separate the coal and the dirt by taking advantage of their difference in specific gravity. The simplest operation which illustrates the underlying principle of the process is the fall of particles through still v/ater. If a number of par- ticles of the same size and shape, but different specific gravities, are dropped together into a vessel of still water the heavier par- ticles vfill be accelerated more rapidly and attain a hi^er limit- ing velocity than the lighter particles. Therefore, the material, v;hen it comes to rest on the bottom of the vessel, will be strati- fied according to specific gravity, the lieavier particles being in a layer on the bottom with layers of successively lighter particles above. One of the early washers invented by M. J. B. Marsaut^ for cleaning coal at the Besseges Colliery in France makes use of this simple principle of a free fall throu^ a great depth of still water by dropping a charge of raw coal into a tank of water twenty- four feet in depth and removing separately the layers of coal and refuse deposited on a cage at the bottom of the tank. The rate at v^hich a particle will fall through still water depends upon its specific gravity, its size and its shape. Air bubbles attached to the particle may also affect its rate of fall. Other conditions being equal a large particle falls faster ^Etude sur le lavage de la homille aut mines de Besseges. - Bull. Societe Industrie Minerals, Vol. VIII, p. 387. • . . > '• , .4 ■ - . 'j.T. . ■ I . •' ■ r.j r ' *• *' : , ■ ■ "li) oCql; .. ■ ’ ■• :• ■ ..cl:.', I'n I . ■•■: '.S . o \ I ^... ■ . u .. . : -■ ;.: . ^ ‘ ‘ ^ J V ■ ■ ' t " , , • J* ' V Srt ’ ) ,i i. ' 4 '. ' ■ ^ 4 ^ ‘ ’ _ * ■ ' ••, * 154 * “ o’»e'^V ., . -^V' ■ = •• ■'• ■ ’•* • • •• : V / ^ J. . . ^ 0 '' 1 O r> i . 'I / /i • j . ■ I I 1 - J ct • - •■> V .. :-1 < i . j .i 44 than a small particle; a particle of high specific gravity falls faster than one of low specific gravity and of particles which Just pass through the same screen, the round grains fall faster than the long narrow grains and these fall faster than thin flat grains. Density and size also affect the rate of acceleration of the parti- cles while they are attaining their final velocities. Of two par- ticles, which ultimately attain the same limiting velocity, the small heavy particle reaches its full velocity more quickly than a larger particle of lower specific gravity. Several text hooks on ore dressing give the derivation of mathematical expressions for the laws which govern the fall of par- ticles in water. Herr Bergrath von Rittinger, the earliest author- ity on this subject, gives the formula: (1) V « C^D (S-1) lIThere D is the diameter of the particle S is its specific gravity C is a constant This expression is derived from the fundamental formula of physics V by substituting for "h" the value of D (s-l), Rittinger Justifies this on the assumption that the velocity of fall of a unit cube is equal to the velocity due to a head of v^rater of unit cross section v/hich will support the cube. The hei^t of such a head of vfater is equal to the specific gravity (s) of the cube, or when the cube is falling in water this becomes S-l and for a cube of width "D«, D(S-l) V ss j/sgh then becomes V =s yfegD (S-l) Richards^ says that Rittinger* s constant in Equation ^Text Book of Ore Dressing, p. 264. . t.: L i.Vj.s'i;- ,,. 09 '*. T|. ■ . ' ■' ' •;. ; X’iS.'^ .v cii ’Jl ox^ioaqa ,c o:zq ■. 'ifv r* -*' '■j:,i'^. r.i *-; hriinn •' , 0‘ * ^ o:iJ f u.’t.CT *' f 4 ' ' .11 "'x: , J‘ V.J11: MiiiW n 1 ix-j 'i.jx , Li’o'riBu t-u I ■ ■'lii:!." jj'^ ' .L* : ••]; or'ij I * ‘ al L^: ' i \l c .. .-. 'ix j li • Jo rts . i-oi o J- J j : u £xi1 nSl, jsdOijfil >X»; , ' i ■ ‘ ^ ,, VKi:,; 13W»A '' 5l0i*T''-7 ... '0 5 X 0 f.. ‘ Xv'.'l'! v^T... S^' ''* t> tmjti •■•r.o’ , X_..0X.J'3CtDdv' , : - f C. •-» t J ^ 7 •.t ■' ... •'O'* i'.* n:;,-!,* ■{ ■■.'i' : . J '-«rt‘x o"' U' • . ' £-• ) ''ti- QOUj.’ ' 'i, ...ir -. 4 '. .vv >, V;M V l;.. --iS , C ..Jr nnv • !''rl J?.r 7*1' :■• ‘i tfOiaxi T7 H ••' ■i j": ' ' ‘ c^^^ VJ -hl^^zr. I f ■■■^:r(a '..fi V .i ‘>w ...» t •.' > .w' •: :i.' ,*u;.ia..a o.^'J :: i;.I -i.Xii «li,. ■' ' '-■ ■ ■ iou.Cir* " ." >..• .r-.:*8pr ■ 9 i4*jol. M '■•■^ '.' I ^ .h? > * . ;-3^yE'tc' .O' V'.} v^J. ." T'. ai'L ori* :•.; .i it'' £:>-*■ •••7 lU V- ■ :■, -’.I ''..''i *' ^ \ - 7 '.. r:or r ^ f • . ' t* \ ; ■■. • . •= >1 I . -w J ■ ..j :rro;' •: ; ' -j 1 r\ : >'jL.,..ir>i f*' '^jx' ; CK.O'j^c'j A0o-‘ * 45 ( l) seems to be made up of f 2g where is a factor due to fric- tion. For large particles falling rapidly this fomula is checked approximately by experimental results. In the fall of very small particles the effect of resistance, due to the viscosity of the liq- uid, assumes greater importance than the specific gravity of the particle and the rate of fall follows another law known as the law of viscous resistance. The formula as derived by Sir G. G. Stokes^ is (2) V =: K (S-1)I)2 This formula, however, applies only in the case of very small particles. Richards^ gives the critical sizes for quartz and galena as 0.20 millimeters and 0.13 millimeters, respectively. Rossbach^ determined experimentally the falling velocity of samples of an Illinois coal and of shale from the same mine re- cording in every case velocities lower than the velocities calcu- lated by Rittenger’s formula for average particles, but the general relation of velocity to size of particles was approximately the same in the experimental results as in the calculated results, that is, when velocity of fall was plotted against size of particles the experimental curve and the curve of calculated values were parallel, but the experimental curve sho7;ed consistently lower velocities. Richards^ secured similar results in experiments with anthracite, Mathematical and Physical Papers, 1901, Yol. III. ^Text Book of Ore Dressing, p. 264. 3v/ashing of Illinois Coals, 1912 Thesis, University of Illinois. ^Development of Hindered Settling Apparatus, Trans. Amer. Inst, Min, Eng., Yol. 41, p, 396. I I - oJ ox;'; to:: r> 'it *<•. »' . ...• 0 1*‘ -■/•i 'i ' r, ,•;{.' • •-. '..:■} { t, • i ► -7 i.- '', 10 ,: iii V T' . t T '•* 73 .1X X *. < ■ “^ 01*. • • ' ‘ 1 r. .; ♦ T 0 1 . Xl-.T, to ', i •'• O.fJ •* •1 X.’ivCdraJT' .Xxoio.r V ' 1 c ^ • - , ■■' nriu? t ? : 'v: ': 0 : u r.'^le er(u e*'*.oiJ-i V . , . * 1 vv X.- v.-i. jiHoSjlj O.iv** 1'. ■ 1 < ■ ■ ’ r. ' t , i Ji :i^: :X. ) 7 • soyuj^n.^ , ■* .a'J . ■; . V. ,: lOi'j ecu m iZo't Sl >^1 >0 .. iXf. v.d" '! 5 HI • flOki O .-fl’ . ; •; 3t/oi/r>«i V -••3; ••; ^u; Vv'-'V . . •;. •- r.l > ** S , ^'.:.r< ' , .■ ^ r. ■ ■-'■^ . d ’ij.H,-- 'tio't , ao . i. . , ■ t • : / . V - . .-’ C r, >*i :;.1 J ,, •■: : r* ' .. - 'T c-n.it'r -'tr : i. .* noi'l - sX^ri. :g *- " ■ ■ '-0 - ■■; J- :: -jj;'iV „ U ;- ,' •CfiWtil ; iiLiifl . iXiidflC . I'fxn 310- ',>*,0 a i an»I. - - .» • j ^ ai r 5 ^rf— ; fj o>i -:’ pic.'tiXli '15 ‘ic^ noLqct/- ;5 P X w ! 0 1 : r •■• ** r / j r i j ; nXI> i - ''■■ • ' * . ' ‘ r i-x p^-iev- 'io’: x-X 'o J’iiXjjnZ-t ':< ii!.' ;i 9> quXxJG^'i fil 6:;Xi.'; -C i.V':- ’ir- 'io X>< X ' ■ 'v-X J V aexlw. , o/s*/ ■ : (Si-l) V 2 = K\jr> (S 2 -I) kVDi( Si-1) = k\Ij>z{ S 2 - 1 ) Di(Si-l) = D8(S2-1) (3) = S2-1 D 2 Si-1 This equa.tion gives the ratio of sizes of particles of specific gravities Si and S 2 which will settle at the same rate in ^Specific Gravity Studies of Illinois Coals, Merle L. Nebel, Eng. Exp. Sta. Bull. 89. 47 still water. This is called their free settling ratio. Consider- ing coal of 1.25 specific gravity and shale 2.70 specific gravity this ratio is 2. 70 - 1 _ 6.8 1.25 - 1 “ The ratio of sizes of equal settling particles of coal and shale secured experimentally by Rossback check the formula closely. These experiments were on coal of 1.21 specific gravity and shale of 2.58 specific gravity. The settling ratio determined by experiment and the ratio by calculation are as follows; Experimental average for particles above .03'* diameter 7.0 Calculated ratio 7. 5 This indicates that, theoretically, with a raw coal in which the largest piece of clean coal is not more than seven times as large as the smallest particle of shale a cleaji separation can be effected, but if this ratio is exceeded the fine shale will re- main with the clean coal. The Natural Middling Product in Raw Coal. The parti- cles in raw coal which are to be separated are clean coal on the one hand and shale, pyrite, calcite and gypsum on the other. The fact that these four impurities are all much heavier than the clean coal makes the removal of particles of pure refuse comparatively simple unless they are very small, but the separation is always rendered more or less incomplete, because of the presence of mixed particles, part coal and part refuse, which are not broken apart in crushing. Such particles, of course, are intermediate in density between clean coal and clean dirt. A third class of raw coal par- ticles which give great trouble in washing consists of broken frag- ments of bands of bone coal or light carbonaceous shale. These particles also are intermediate in density between clean coal and > r' 4 . ■^ 3 .' : ..0 - .;: I t I 1 ■ ‘ M • - . - ■■ Ij -O'j f - ■ ^ 1 'i. ' ■ <\ / f 3 >, ' - ■ ^ I J" ■•• .. '■ :,.t i i ! f ■i ft jO^ r- . . . ► ■j t fii. S': ■/».: r:* i j e . .u:) •v. -i ■ « <■ > v/ (. C I. O ^ 'Tlf t 0 :. ■ W. ['z ■' . Q . ./.T . ' ..;: • : L J :;■ /r ’ ' C - : . -S/ 5*X - li ’ ^ ... "I i • J, . O \) ' C-. I ^ J 48 clean refuse. The mixed particles and the hone coal and carbona- ceous shale particles form the hulk of the middling or secondary product at the washeries. This product is either crushed to finer size and rewashed or used around the plant for fuel. If there is a considerable proportion of this kind of material in a raw coal it is very troublesome for two reasons. In the first place, such par- ticles are very difficult to separate from the clean coal and in the second place, if they are removed, it results in a large reduc- tion in the amount of coal produced for a comparatively small im- provement in ash and sulfur content. This constitutes what is probably the greatest difficulty which is met with in washing coal. It is particularly serious in many central district coals which con- tain, when crushed to the size at which coal is commonly washed, a relatively large proportion of such material. It would seem that the mixed particles might be eliminated by crushing fine enou^ to break the coal and the shale apart, but the practical value of this expedient is problematical. The effect of finer crushing in the operation of washing depends upon two opposing tendencies. First, the more finely a raw coal is crushed, the more completely will the particles of impurity be detached from the particles of clean coal. Second, the finer a coal is crushed, the more difficult it becomes to separate all of the detached particles of clean refuse from the particles of clean coal. The bone and carbonaceous shale cannot be cleaned, as the fine ash is inextricably mixed with the coal and cannot be separated even by fine crushing. It is, however, possible to remove such par- ticles entirely and discard the coal as well as the ash. Specific gravity analyses of two coals are shown graphically in Fig. 3. ■' r'a bf.n:x!c Oil? r.’isU *0 T i: xi ,■ i' iir T.1.J 'ic w/'J’ rr:-. ; . i)i _ > j>£iL : ■> i V/Zi-. > .10' * *• ' •' “ ’ ' 1 -- -i Oil!) O'tr-i 'V z' . .* . Jvuiiozz- T ’ " * * * A*;! q or^* Jini-'OTiJi {^0it J Tfo ■ ),,. j.vyr w -itcO . -'I r! ni Xi. i •>-!'* /L~ »■- i r j * ’i u*i ■:;j pf . ,*£ ^ « ' =*X t l •) „ :;I . jitOiC.'.’iVi: o-’’v ' ot; i.^ ; \jfu o*i»l V'lav -V- •• ■• -n «■ . t.; fmlol. , VnZ ’ 01. coot; - * J , ■'■ .n ^ r-rkf- J t .. f* r ^ I* ^ , * I ..J. ^ 1 ‘ -iC- 5 J:.-V L i X , • Ui P . -lo'i ^ PO AvC nl.r'^ > - * j t . A , Jt in ii‘> :.. b Xx'rX.:i? -.•• xn. '« T) ' ,‘ r ^-r. ^ •ii J-riO£Pii;V 0 f '4 \f.::' iffoie ^ r \£:x >■- - ::i 5>ia • - J-.-^ .o' ii oi’J. v' : •■ *3.. 'tv .lO .C'**: •.V.v l'vj5} ., ■ '■ ; c‘; or’i .£ I'l | '^c i . ii . r .."r o v - DP*.-. .! j .' 3 i '’ '• p' :;‘ Xoiv'i ■..< o;.* :a-u it 9 J.'I. •• I ; r: :b^ . 'x..^ J- •‘■r;p'Xr,wO :>. .^ >L'>s»'x j o-b nx -,;;x '-O.;/ : >c wOr, i.o o: - * 1 - 0 IJ , uei a o-i v.l ■••■•.. -I t'- , xono-..: c v::..oo.i(^o xiot'" iiirKOqj'O vr 1- 6 q ."i: / v/o^ 0 :■;. LuV’ p-x^- • ;j ,* ';j.-'-:o fix I ;oo V.UH /j \Z^ni\ ^to:n • ' i x-:c:- .; Dio lo ooXoi.l'i ov.'v" .;00'i ■ bo "'or’w g .' v" trD^’oi J”i-''’P fi| ^ 1 .'! - G.o.: :• : ft'tosn Pt. , '»i-fG'-tD :-;i Xhod Jt; 'lOitxl 5 ;J- ,*>r.ooo.:r i .... •' ■ .0... a:o'^ :in:;co'i :\ vIg '.p oo‘oib'1. ,. b :>b pd:? “io xi^ n3 ^■zz»q(^ o3 I . '’ >0 y To O.-J :.. . .:..’‘j.^y dX b Oil.MiP,. eijv i„. : -00 n-j .;'i. ■ , oo' .?OXT -Til /.-■CO Grr.f •f -» ;::''y'. ; olZi :yc)iu G'’'«>vy/ oi.Txooq: *• r.u £i'g.’ •'■ • I -oa p. « • t * A. ir r ; .. Gii-I.j ,'rr, /'^.vorfc o'r.')-. i »■■ i - ■ . - . - 2f ''xa.;:.. -,1 r XI .1 50 These show the percentages o f material of different densities in raw coal crushed and prepared for washing. The lengths of the horizon- tal lines show the relative proportions of the increments of the specific gravities indicated. Those included in the bracket make up the natural middling product which gives difficulty in washing. It will be noted that the coal designated as non-washable contains a much larger percentage of this material than tlie washable coal. This difference in percentage of natural middling explains in a large measure their difference in washability, . These graphs show plainly that raw coal consists of a mix- ture of particles of all specific gravities between that of clean coal and that of clean refuse and that no definite natural line of division exists between the coal and the refuse on the basis of spe- cific gravity. The zone of separation in actual coal washing prac- tice corresponds approximately to the middling zone marked out by the brackets, or perhaps a little narrower, say from 1.35 to 1.60 in specific gravity, but shifting up and down somewhat, depending upon the grade of washed coal being produced. The ash and sulfur per- centages in the various fractions of different densities in these coals are shown in Table 3. t 't;. ?;r-o;u ‘I :.,.i r,:{J , : . .J.J ■-t.' ■M'^n.rriifc :•• .’rt l'fv r. x. 'lu^eri -^^W' rfj* \ '^- — ■ A'l rini'v.T •• 0 , • V I ' J. X" C : X' ci/ij ’ '■'■'■ .•■.;.■■ i y,I. L?!;! " ‘.‘ -J Xr J • A- ', • , . ,r v * i ^ ^ I ’ c pi*“? \ ;X iri ii ■’ il :; T j ;>n'; iAi J - 't'} ’^"‘... f XX i . ''. , l^ui 1* ,■/. ... 'iC^U:,- . ■ ■" V ■ ri e>c. , ■t': :1it5 /.'AiC-ai T 'X k.a ’ *‘i I* ii ’ •*■■ ■- K ' '►V • . - 4 , V 'X.iq 1rc( c;x4w' '-J J; .' vX h -'i_’> i»ft/'' . .•' 'i*: ■:»*’•* <5c,/ .4'r'v.i « »= i , : •’ r n ” '"i : r:: ‘i .. . f»'» ^ :■ i . ■ •< i .5 •rroTT ;p' .l!*a i :oo ^ j :> t\X ,*r J a ■• X fM. . :. ,:M ax' fi;, '.,v f!.'r nl h i ,i c/ * n a t (TA-Or*..' I:IjS 3 5 51 TABLE 3 Specific Gravity Analyses of a Washable and of a Non-washable Coal Washable Coal Non-washable Coal Specific Gravity Per Cent Ash Sulfur Per Cent Ash Sulfur of Total Per Per of Total Per Per Sample Cent Cent Sample Cent Cent 1.30 73.35 4.64 1.72 55.9 10.1 2.91 1.30 to 1.35 8.74 11.27 2.14 20. 5 13.3 3.35 1.35 to 1.40 4.93 17.78 2, 39 11.8 15.4 3. 45 1.40 to 1.45 1.82 20.32 2. 52 3.8 19. 1 4.39 1.45 to 1. 50 0.39 24.60 2. 62 1.8 22. 5 6.18 1.50 to 1.60 1. 12 29.90 2.80 2.1 27.6 9.29 1.60 to 1.80 2. 13 49. 53 3.43 1. 1 42.7 13.30 1. 80— 7.52 84.04 13.63 3.0 60. 5 34. 12 10. Relation of Specific Gravity and Ash Content PJl Co^l. This table giving the ash content of fractions of the same specific gravity in different products from the same coal she that a defi- nite relation exists between the specific gravity of raw coal par- ticles and their ash content. It will be noted that in a given coal fractions of the same specific gravity have practically the same ash content. The coal samples were divided into these various pa.rts by immersing in a zinc chloride solution of 1.25 specific gravity and pouring off the float then immersing the sink in a ser- ies of heavier solutions varying in specific gravity up to 1.80 and analyzing each float product separately. In 1893 E. B, Coxe, in an address before the New England Cotton Manufacturers* Association, stated that there is without doubt a close relation between the specific gravity of coal and its percentage of ash. A great number of specific gravity determina- tions and analyses made at his laboratory at Drlfton, Pennsylvania, 52 led to the conclusion that for a given size of coal from a given mine, a specific gravity determination on an average sample will give very nearly as accurate an indication of the ash content as will incineration, althou^ the relation between ash and specific gravity may not be the same for different coals or different sizes of coal. Nebel^ gives the figures for ash content and specific gravity of a number of bri^t coal and dull coal samples from Illi- nois mines showing that the dull coal in every case was higher in ash content and hi^er in specific gravity than the bri^t coal. The curves in Fig. 4 show the relation between ash and sulfur content and specific gravity for a number of coals which were examined as to washability. The ash specific gravity curves are all practically strai^t lines showing a fairly uniform increase in ash content with increased density. Since the calorific value varies quite uniformly with the ash content, the relation between B. t. u. and specific gravity will also be fairly constant. 11. Relation Between Specific Gravity and Sulfur Content . The percentage of sulfur in fractions of a given range in specific gravity in a coal shows considerably more variation than the ash, yet the approximate checks were secured in the coals examined and the curve, Fig. 4, shows a comparatively uniform increase in sulfur content with increasing specific gravity. This will usually be true of high sulfur coals containing much pyrite. Low sulfur, hi^ ash coals on the other hand, may be very erratic in this respect because the increased wei^it of the heavy particles may be all due to ash. Cases have been observed where the heavier raaterial con- ^Specific Gravity Studies of Illinois Coals, Eng. Exp. Sta. Bull. 69. , TCf.t t ’■rfj lA ^ ^ V ' jv-.r; ,.i - ~ * ! J i:4> f; . ,; * '.' i.r * ' - • ‘ - ' : i. -jfJ.; ; • 1 Xi'XM^: v*£9t t'.r ' • .. .' ' ■ .' ,TOi^.«rA •■' :o V ; -cc ^ ir ‘i-'lli -ic'c :i;.->u, r .. • V- . i - , i. ^ • \ ■ ;ur -ii • •■ •• ■ .* ?ftri ' j;-> •VO ■ il(..' ■ XdOo .* , I't iC I- . ^ LOT’. ic ’i--’ •: r • -''rik/i ■ lii r '* .t ' J-. ... ** .-J .-r •v‘ .,:xv -X- '..;■* ' . ,; ;•: wpc:. ' -.Jrrbo * ?;*' iioir :. . J . , : >; J. 1 •r ^■ ip; p:£T ■‘tioaqn Z; iiji V ■':.& aM- ;v - *'r^-ob .-a:;*! i^psm '■ ir. * '^ i .' ■ - ■;. ‘ or.i;.. . --'1^ oi'ii.r. '.-... .•• .r: ' •' ' ^'•- o- 'X* 1 .. *4'. ■: ;', ; o I * • ■ ‘ i'l.’ ■•'■'■:' ■ ' L'. «i,.' : ‘ v. , ai ly ■' ' rUo^rlQ .,.' I ' -:qq& ® . • .^VT'/C *1 ’ - • * ‘ * .* - * ■* w 1/ . nr.--' nci:,?, :. -i-;' ^ aoi-r.. r :> '. .h '1 1 •r ... . f3,: J ■ ] .• V'i*:*/ ■■ — i-v - 1 .• J '•; '■'I rf » «• ♦ »,^- ;■ ’i.P, J’l ; / -k ■■ )TD :,i 54 tained less sulfur than the raw coal and the washed coal contained more, because the sulfur being mostly in the organic form and com- bined with the coal was slightly concentrated by the removal of heavy shale and slate which contained no sulfur. Such occurrences, however, are exceptional. 12. Distinction Between Coal and Refuse. Theoretically a perfect coal washing process should enable the operator to make the separation between the clean coal and the refuse product at any desired specific gravity and, as the graphs of Fig. 3. show the raw coal to contain material of every degree of specific gravity rang- ing from a little less than 1.25 to over 1.80 and of every degree of impurity between the minimum in the lightest product and the maximum in the heaviest product, accurate definitions of the terms “coal^ and "refuse" are essential. To formulate an abstract scientific definition of coal as distinct from refuse would be a difficult task, and would probably be of little value in the actual adjustment of a washer. It might be defined as the moisture, ash, and sulfur free combustible matter of the coal or limited to the material derived from the original vegetable material laid down to form the bed, excluding interbedded or subsequently deposited mineral matter, but neither of these defi- nitions would be practicable for determining the standard of purity for the washed coal. The distinction between coal and refuse as it applies to practical washery operation is purely a problem in economics which must be worked out separately for each individual operation or each new set of conditions as they are met. One of the most important considerations is the use to which the washed coal is to be put. CO TOv ^ i fii ; ifd^ VXi^J •: r.l N'C^oo:.;. : f n:;:io • - 'i .;* jooo ‘..j / ^ .1 :. (3 ., - cjt: ; :'j • • ♦ ,.w - *•.., ■ •'■ .i ' ■■'• oJcl€ ftl.'i'fii 't£vco.'. ¥ -• ' ' '. :r.. ■ •: 7 r u; :’oA' .. . ' ■'1'Xtrt- •■> '-.-.'•j ■/ •• 0 afii- ■ * ' ■ r.olJ . f < • ’ '. ‘"'w' ^ ••' . ■ 'i.v J y’’ -. t; bti^Xr^:': •■7, .. • -.►.■■ C- -j . ,:oo 04 Tcwi: 0 '- ■ 0 ; • . ; X . ’It V C oi ^ f, 0 * >- ;V - ,I :i I..:)! i - •' *;i Ta/a^ai *. V *;4 i-tEwiicii. to . . ■ ,,f ft'r: ; -1 i.l ttirniuV^ ' t 3 . . " •ih'z'ix** ■■ *'S. ,K. '• r ' 1. ' -■■ ■ u . • , '^ i i'Q /C j j ‘ ■•rc-J oT- Jb:i , '• . * V (. V ^ X ' 7 ' ' - j t,!Q' ■ •, ‘-C\ J'-: •: .♦■•:- 4f ' ;■. . .: oi f2oI ' ■/ Z. i, : r - J rt u ,>^^i .«ab '■' : :Trz i :■ :)• lM"r'7,r.r 0 ♦ -j ^ j ts^u' -T. Ici.oo - ' yVv^-* ■, ■ l-tulox , -OiJ rrto)’ • j a. nil.'vJ.’iJJ ; 'i "*■ ' i '■» ■ , .^/ •': : ::cJ ' .7. -0 • ’ »; ’■ :iO(f .i • I J • - *.• 01 • - ^ i -»•'.* '5. • ^■‘ ;o \yxf^ ' ' 'i, “is ■ -i** ' • ■ ■''. ■ .t . .■-. i 1,(00 J 0^ S 55 On this basis coal washeries may be separated broadly into two groups in which the conditions are altogether different^ first, washeries for coking coal, and second, washeries for fuel coal. A washed coal which is to be made into coke for metallurgical use must meet certain hard and fast requirements in regard to ash and sulfur content and if it can be made to meet these requirements it will have a much greater unit value than if it has to be used for fuel. For these reasons, as a rule, a larger proportion of the raw coal must be, and can profitably be, discarded as refuse in washing coal for coking than in washing coal for fuel. For instance in washing either of the coals represented by the graphs of Fig. 3. If the washed coal is to be used for coking, an attempt will be made, in order to produce a good coke from these high sulfur coals, to make the separation between coal and refuse at as low a specific gravity as possible, say between 1.30 and 1.45, althou^ some of the material discarded as refuse will, as shown in Table 3, contain only about 17 per cent ash. On the other hand if the washed coal is to be marketed as fuel the principal object of washing is to im- prove the appearance by removing the more conspicuous particles of pure shale and pyrite and the separation should be made at a much higher specific gravity, removing probably only the material heavier tlian 1.80. The increased market value added to a fuel coal by wash- ing is not sufficient to enable the operator, without financial loss, to throw away as washery refuse any large percentage of his raw coal. This is the condition which normally exists at Illinois washeries preparing coal for the market. The economic limit on their refuse would be zero v/ere it not for the fact that at times washing makes possible the sale of more coal or the sale of sizes If '^1 o,*.,; V ..0 cT-:' •''d , (?) •; v_dfi ■ ■’*j, .j-; ,Xvv ’.00 tfl f -.iz'd’ -hO jj ■‘• - a:, - ad? a ■ -*. bKj rfoi ' ; .— ■ 'O' 0 /1 *fw r ? . • ..:• • ,I«oo : . .a .. . ^ ' 1 ? v.u'. a-D v/'.’i • a* '. / ’'jiriw liico ‘J* ?/ .' ■ ;V art* 3 -ilt/j.O'i d. 3 -;. d 3 *n»’ fCi" •' . '' ■ 3 d - 0 ^ ‘i r... C- Vi'- 'Ijt .? odi'.oo V u " ■a * -x .5 ' a '*• t \ » 1 i- ^ , «% a , - *-;' 10H . >.1/'^ A •' ■' ■ •' ' « •/'■■■* X.'< ’ dTl -i ; .1 -.• 1 ' , v.^•iL^?. t'ic.-) -' X'.i .1.,.. V .ti ■ :f y_;ii.^oo «*v_ 8 n 'j ■jr'j vcf O''/ *• -T^xt'ax .: 4 . >'' ■ “ i V ^ V ' 5 •* ' * J[ ' 1 ' i T ? • •• *ji , t ■I' vj»(fJ ; . H M ■} -';,£■ V -V..- .. 1C I. .“> ■» •; oJ • i t. t 1 •'*' ■■■ •..! X-'oX .1 , aj- k ; d ;'i -■ ? ? / a:D*,tT c.t vfi).v.rrv,j ^ nii. ',,dAr«'r' •' ■' t,.r '*'r •j'jlii .Tft 4 'I?di< 5 ;B Or‘' ■ 1‘7 '■ . ^ *4 i. .-: /.I. a ?:jk .if.'/- •. o f od :i: '/vufiiBX Vvi >.j‘ ■’I ■*. •C'j 0 !d '".'Oil . Oiid n&i-.-'r' «>';j:i'a' fiX'iJC , ’ ■ ^ 'X'. C-i'a 'JBf 'C r . ■ • ’*»**' ^ i *, » » -*■»- - - : : d. ;cr^d. : 0 'X 3 ’.T "?• - ^ c • X ©.is ’a i .u.“j t/ .j n.': j od'ilL:;.,.. d (Ci! '.1 \,nr. ':r>r\ ,-r \y' ,'V^ y : \y-’Vy V\'r:- 'd - , . .. nOiJis'j'tOO . .'5j v lii.* . 'iO * a a*i V Sy:C:) .i iixc.f.'vcv^ id d . d.i.'s’ . r; t . ov .: o ; ra^-'o-v , 0 a.: . T 1 ’ d a ^ad -ci r.b‘r’ - ^'Ticrt tJ ’.i.. : > rt ■' ■ ;T-'iv li r ^'vi^Qu. *. o,t^ 1SVC-i.:-i 0^^fv.« vi JiSGOfT c ' O',' o'Z ovri :"'r,.:V . : o’la l)?7.-'s r»rl?f ■•■ :,*'•' -. 1 ^ ir\ • c';; .’j ':I ’ >•: • i. \.n:arl‘:'V' 'o** r.Ta.-r- -^ 1 ' cdlftillr* ■^■* > .• I> >» -. • . •• '*- • ,, -,.. .. ■ . i-.... ■ Vw * ,-•'.■ j #• i*; 0 ( 3 >r: * L • ^ 1 . i- - * ■ ' »% f . V ^ ? .. - 1 ^ ' . _ * ‘ • .-• ,,i J •'. j'l'.M.T IJ ' - ' ’ •■*“■ X>^cr) - 3 ^;:’." , . * ' ’i*? ’iifu; ri"- 5 *xi.-ii Ciiiii; ?i bcii ril i J • ■. 1 J A ;> 9X1^ 0« .( 'r-o itiiJ., 3i.O «» iJ - '• •o-' .' -Tr ■ V- 7 *x ; • r:--:* a -lii;!* '•* ' ." •- ■• -I ’ >icuv ' j ir-'i i • 4*1 oiJ’ c] ■'■0/ ■. ; ni.,-. pn „ ' ' -‘-i •'■ 'i . -j- ^’rarr njox I ' . I Mr- •■ I’ .ii TABLE 4 57 Recoveries and Ash Contents of Washed Coal Prom a Sample of Indiana No* 3 Coal Product Number Per cent of Feed Per cent Ash Cumulative Per cent of Feed Cumulative Per cent Ash 1 4. 8 5.03 4.8 5. 03 2 5.2 5. 14 10.0 5.09 3 4.1 5.32 14. 1 5. 15 4 2.9 5.64 17.0 5. 23 5 5. 5 5.77 22. 5 5. 36 6 5.2 6. 13 27.7 5. 50 7 6.1 6,45 33.8 5,70 8 4.8 6.97 38.6 5.84 9 6. 6 6.60 45.2 5.95 10 7.8 8.20 53.0 6.30 11 11.6 10.20 64.6 7,00 12 12.2 10.85 76.8 7. 50 13 8.9 18. 57 85.7 8.70 14 7.8 45.05 93. 5 11,70 15 4.6 78.00 98, 1 14. 80 16 2.0 58.92 100.0 15.70 In Pig. 5 per cent recovery is plotted against per cent ash in the washed coal. These figures show the possible range of adjustment of the zone of separation for this coal, giving on the one extreme a maximum recovery of 100 per cent with no washing and on the other extreme a recovery of 10 per cent of the rav/ coal in a washed coal product of 5.10 per cent ash. In any case the separation desired is the one that will give tlie largest possible recovery of clean coal which will be suf- ficiently pure to satisfy the requirements. This is the condition which will result in the greatest return from a given tonnage of raw coal treated. ,N t 4 ^ is r ‘ V -’Z ■'**-. i f.'- 4 . M 1 j percent yie/c/ /o 20 20 40 \ySO \ ,60 i I 70 \80~ Po /oo / Z 3 .Percd\ftt Peh 5 > M // }2 /3 U /6 /6 / Z 3 4 2 e 2 8 ^ h N /Z t3 h4 ^6 6<6 : Percent A^h \ | : Fig, 5 — yield Peh C^rve^ fable V^a^blng ^b'st on 0 — Coal., _i f 59 CHAPTER IV DEVELOPIJOUNT OP THE PRACTICE OF WASHING COAL 13. First Metho ds of Cleaning; Coal V /i th Water . The ear- liest reports of the use of wet methods for cleaning coal show that from the beginning the processes and machines used for improving the quality of coal have been developed in connection with the met- allurgical industries and have been brought a,bout by the demands for better coke. Crude methods of v/ashing coal, by drenching it with water, were in use in Germany, France and Belgium in the first part of the Nineteenth Century. The first results recorded concern the experi- ments of M. Marsilly^ with coals from the Valenciennes district. The apparatus used was called a gailleterie, and consisted of strong sieves* upon which a stream of v;ater fell. '’The largest pieces, called gailletes, about two inches in size were retained in the first sieve. The gailletins, or second size, were composed of pieces of about one-third of a cubic inch and in the third, or tails sieve, a.ll the friable earthy and pyritious impurities accumulated." The first product 7/as further cleaned by hand picking to remove coarse shale. This produced a. good coke carrying 6 to 7 per cent ash* The second product yielded a poorer quality of coke of 7 to 11 per cent ash. In a similar process used at Comiaentry Colliery the crushed raw coal was flushed with water down a sli^tly inclined trou^, with gratings placed across at intervals to retain the coarse pieces and permit the fine coal end earthy material to be %ussprattte Chemical Dictionary, p. 94. o T.‘) .) • .y. ' 1 . . \'j c'‘ori ' ? ^., ; :• * \.r , *.' ■ l ^ • '1 , ni ■> . ■ ‘t < 'it:; 60 washed on out of the trou^, A method of removing the cla,y or shale dust from coal by drenching it while on the screens or on the car before shipment, with a stream of water was not uncommonly used in the early days of the coal business in America, In the anthracite field especially this process was sometimes referred to as coal washing and has been confused with the specific gravity separation now designated as coal washing. These were merely wet screening processes which, due to the fact that the refuse and the dirtier parts of the coal are usu- ally more friable than the clean coal, makes a rou^ separation be- tv/e'en the best coal and the dirty coal. An improved form of trou^ washer similar to that used at Commentry, but with low dams or rif- fles placed across the trou^ at intervals to arrest the flow of the heavy impurities and cause them to collect where they can be shoveled out, was commonly used until comparatively recently in the British coal fields. This was the first kind of washer in which a separation was made between coal and refuse by virtue of their dif- ference in specific gravity. As far back as 1826^ a washer of this kind, then called a step washer, was used in the valley of the Tarand near Dresden Sgjcony for cleaning slack coal for coking. "A continuous stream of v/ater from a superior reservoir is directed upon a flat chest, the bottom of which is formed of two steps inclined 1.5 inches per foot against the stream. The second step is lower than the first and is succeeded by a table of wickerwork or a perforated metallic sheet upon v/hich the washed coal is drained. A low flat board across the ^Coal V/ashing, Arthur Beckwith; Van No strands Mag, , April, 1870 : ■ ■■ * 'Ijr V . r..' ’>*' v r "fcr.'aHOorir ‘ 'Jr;' .< r«v 2 .r: V . n: .•jt;:'-' > ;JL (nt j v.'i . .:0 I • ;.■■'■ •: T'US'^; V- . • N " lid -c n ua J ^ T j -I ■ ■ % ^ /: i. '’'M't i. :• 31 ' •.• \ C '.»*■- s 5 T« ■ iJ- top rteO'Jv< 3^4 das ''• ... . i :'h 'r»‘'Oi‘- ■ .r. '> 4 " •> . v: . : .ii .( 3 o'; •• . f * n ■* ’ ■ •« i. 3 *t 3 } ;^.D 11.:' 13 a.'^' . i'X". Ttv . \- I:’ •?c fi £<)^Q0 I :'ro • * x» ; • c? 3 f 'iw nil' .ir 'b ':o ■. ■: n: : i ^ y > , - 1 1 'I i ' V -1 rui i i i '.i' Hi oj" :c.. '• -V -rv:_ 3 ' " '* . 13 m. ■T L ..i 'tnrfn,* ■ ? .c?' «.’4i : li. ' -.' • • i-' ’t 'll- IP r*‘-: / J . I C-.. .:••;• •,•?- \ r,!.|lG&,,''..vr u : . r.l fvi ’•''T ^’r 1 .ic., , 'O lid ..y .;i ’‘‘ "t.j \ ’■■>-. ■, ->•; 7 . 't;oX ...V O-'v *J jOG7 y. . ^ U r,i : 'j’l .’t’ * ..Oi} '.■)■:•' f'- ; .‘'r(.)i:‘ ••..’■ ,d. .[-..Cv-ri n.;.>Ja C'..’^" I 4 30 •.'■pii.C ; ■: ., 1 - o T«>' ‘..,-- 0 *:, '- ^ 7 i C' Vi 9 € •: i '10 /. 'i .=? If Wfl t -'\ ■'r 7 aOv 3 '.? ',l[; ;j & c ,■'*.> Cf . ji j S'? o.vj -f .': A . o ’/ n '■ '0.* n„ f ., • r J ,CC.'i/*'r '-oi oio'lidti • ■: -'lOT-idAuiv ‘fA- o.- / 0 . 'i .f^ 5 »no '■ ot r 1 ' I*:” 11 r • r ^ ’*f xb i:i I^C/V i -‘0 » * .-tX 3 V. :'i*bOJi , ^ » .f #•. *1 »l' • r/ i # • I f I '. J« ' V* •**% A *4 4<4 *»| ^ • 4 mU -^'* 61 upper end of each step serves as a dam to arrest the slate, stones and denser bodies. V/hen these have accumulated sufficiently upon the steps the washing operation is stopped for a short time and they are shoveled out.” Fig. 6, Early Step Washer used in the Tarand Valley. 14. Early Hand Jigs . The first machine which made use of an intermittent rising current of water to make the separation be- tween coal and refuse was the hand jig, a machine which was origi- nally developed for separating metalliferous ores from their gangue rock. Agricola^ describes a crude form of jig which was used in the Sixteenth Century. This was a round sieve bottomed basket v;ith han- dles on the sides which was filled with ore and jerked up and down in a tub of v;ater. After jigging for a sufficient length of time to stratify the particles, the lighter waste rock was skimmed off the top and discarded leaving a layer of heavy concentrate in the bottom ^De Re Metallica, 1556; translation by Herbert Hoover. , lie ' r*J- TTrf' o'*w :»o.> V »t . •■•. ' ’• • ■ r:-’.c ? A'i'i'.'io ?. >. '•7' 'c.qsf*. ■ :>:1 -JVOjfei M irt “v i . » T^f i f'r ■' ^ - 1 - •l.t”' - ■'^•j J.i * .♦ . - «»..•*• oV- • ; o.? •r.^j.. V ■•■ ef.trX'Ii'r' : .’ i '.. ■• I -• • , jr;. ©{(# *r-s''^ • •_ .: ;/->so;i frt :vri.< :s; *xc- v . - ^ . ' i '’ X . I ‘‘ ' J. J 9 •* 'J zi .i'‘;-n/^‘Oi -bv^i. 1.2 i ■ u. ■i ; . >•: . b'lf'XlT oii' . i '.V .'. :o -''vriri' /. i. Jz, . ►•:’Vw/ 5 ^:r .’l ■ .. , o -t./.: u>:’.v -.tv. ’•••* -■I'jJ.' -IX 9iff' ', J'f '. ^ • r . , , . . » t '**. » - r ^ % *• . ■ • . I • . 7: ^ LV.i JL - - ^> 1 . iiA-^ * ’ :ici.-'»C 2 .r : *.: ., > .v'i oo 62 of the basket. Q,uoting from Musspratt’s Chemical Dictionary refer- red to above, "In the pyritious coal localities of the Vosges, this process has been practised for a considerable period; but it was not adopted in other collieries till about 1840 v;hen it was intro- duced into the coal districts of St. Etienne Rive de Gier and at Mens and Valenciennes". Beckwith^ gives the ds.te of the beginning of hand-jigging operations at St. Etienne as 1637. The first Jigs used for coal v/ashing were similar in action to that described by Agricola, but the basket was made larger and it was moved up and down in the water by means of a hand lever. Another type of hand Jig which is nearly as old as the movable sieve Jig is shown in cross section in Fig. 7. This Jig was in use in Germany and France prior to 1850^. Fig. 7 - Hand Jig used in France and Gomany in 1850. ^Loc. cit. ^From an unpublished manuscript by S. Stutz, owned by PrO“ _fessor H. H. Stoek. V . t , t ' 'X 3 M'- f oa‘i ' o ' * ,'w'X o-t V’l .^-. v*» 01. 3X x :i- :'oo -X ■^iqo*..-. j‘ 'ioli ?5 f'vi.l :• . oi.'* . •' Is6d ••’ .-* •'■•’ ' - • kvl^ Jt»3(0f/ . ‘•r- •>{ii;!->i>n3lsV bru. . -'’'f ti,h . I rr: ^ .-xofio *^ . X:-": i i . I * ,.,: i:j' . 'i ' ) i '■ ' ■* .' C ?; •'. .'/V X -30 0 *l>iX />'■«; j i - o.ij , 'ooi'X ' .. . ■•.-•••' ’ V ■'■•''•* .:i’ _ .T>*'o,-, W.r.i •■' '>'[ 1 * ’-JOXjV V ^ fl 4* .:yJ*J9ti irwoi. v I, •'/..jXm « • ■ i.f'' V. % * A t ■ A j nc , /. 63 The raw coal to he washed was placed on the sieve in the front compartment of the box and the piston in the back compartment was jerked up and down by means of the hand lever, imparting a puls- ing motion to the water which jigs the coal above the screen and caused it to stratify with the refuse in a layer immediately above the screen. The bars shown above the screen in the washing compart- ment were to guide the shovel in skiitmaing off the washed coal. One man produced with one of these jigs three-eighths to one-half ton of washed coal per ten hour day, 15, Mechanically Operated Jip;s , Stutz describes the oper- ation of a similar piston jig in is^ich the piston was operated me- chanically, This machine was in operation at the Besseges Colliery in 1855, One man tended two machines skimming off the washed coal and shoveling in the raw coal. The two machines produced fifteen to sixteen tons of washed coal per day. The ash in the various products is given as follows: Raw coal 21,35 per cent V/ashed coal 7,75 ” ” Refuse 71,65 « " Slime in jig box....... 46,38 *’ '* The refuse contained 10 to 12 per cent of coal, the slime 25 to 30 per cent and the waste water 2 to 4 per cent, Stutz describes a number of similar jigs in operation at German and French mines between 1850 and 1860, including one at the Hirschbach coking plant near Saarbruch for vfashing coking slack from the Saar district. The jigging compartment in this machine was six feet long by four feet wide and handled half a ton of coal at a charge,^ The first coal washing jigs in which the operation was continuous and the vmshed coal and refuse were discharged automatic- ; T’ ■/ O ' J-'’ 'J L M \c ^ »' • :) .* ?r‘X^ ' , . . • a^v; 'i-.O ■' n.' . tj 1 ■: >c.-X ifi • »Vvy iTC, > 1 X 0 rl.vairrcJ'iiij 7? 5X3V. "ju' - ^ , 'i n '* ; '? o>i(aj5f t I r O i 64 ally were the Meynier and Berard vrashers. The Lleynier washer was first used at the Brassac Collieries Puy-de-Dome, France, where a plant was constructed in 1854* ^ The pulsion of water in the washing compartment v/as produced by a piston pump and the v/ashed coal and refuse were carried out at the front of the v/ashing compartment by the flow of water. The Berard washer was similar, but the pulsion was pro- duced by a piston working in a cylindrical compartment of the wash- er. This machine was exhibited in London in 1851 and in Paris in 1855. The first operating plant was build at the Mollieries Col- liery in 1863. The use of coal washing jigs of the modern type may be said to have begun with the introduction of the Luhrig jigs and the Luhrig system of washing in 1870. In 1867 Mr. C. Luhrig^ of Dresden Saxony began experimenting with the Harz jig, which had been used for years for the concentration of lead ores in the Harz Mountains, and in a few years produced the Luhrig coarse coal jig and the Luh- rig fine coal jig. These or similar jigs with minor changes in con- struction and operation are the most commonly used coal washers at the present time. The Luhrig nut coal jig, (Fig. 8) consists of a rectangu- lar box with hopper bottom having a partition in the middle, extend- ing about half way down from the top, or to a point sli^tly above where the hoppering begins. Upon one side of this partition, is a relatively close-fitting rectangular piston actuated by an eccentric ^S. Stutz Loc. cit. ^Jahrbuch fur Berg and Huttenwesen 1878, p. 85. v:'«‘ •I? /:, -'*’ 1 . ba • I' , . ^ 4 : , -'o.;. •'^' . -oi-* . ' - ^ ". j tTilXXoO. -* J '■ 2 *' ij; , .--Ji /r 'lo oicXiJ.i f , 'c*.3t ni '.'ir-.f ..j i • J.'tjsXs: 6 r,ii r.- ’ :' '' %■ -' -•'»''u* .■•-’■'»i*.: -'.■ \J' 60 :. w'DOl-? " • s_ Cc; - .qaiaD eri lo :trto': : ^ •' > . r , ' V c .. *t f* “ . f .'W ,. *‘«ia 'J' I'l/itet’, - -A ;:r '£cA ^ n*N(S;j«xjsqp«*,_ ji r.:iv*iqit ’'t.irr i . ci i r.“_' ; iii bii:: SCSI .’.1 .sobnixi Hi . ■ •*•'>• ni:A? : I J ■>'^ ■ i H'f 3i.»» Jr’Vli, ’»:CT - ■-•x ■' A ,t ftfis *>0 •,:*:. ^-.hx.iVh.;. friT LW :h;_; ‘"it. : ;: n^Lf t'J-iw ‘.v-.u o5 bi • *lo -.U-:; .... . ;-'o a ,;.: -rad-.t^tK 11 . '.1 r .w. ■ .' .; : ' -*■ ^ - ;■ .:^^r ' -ni ro^ -T V-<« M.£ ? I M V ctL'.i 'iJ i •• ■■' ’ ' tP’i.i’* .;. a nX p- n.T’ ' ;uj*’ *.* » r^i - irt'' .' .;o;) . ''::J /.r-.o *: 'jct : . *'• -‘ .y^ • * .p ox.^c.ri-^»i ... l'.a«.:r>i!l' !'• ‘ O'li't i' iw'ii.i’j ■' '■' . * ( • '» X*’ 0'' JfJti y tT.M' L v.i.*. ; i,- .y-, . .:: ,:oiUv ^ . J - ■- '..•:PVio4 * rff t'^ XOi ^ c/. r .i;Tioq r> o.r - , .■.>; «ii.. mrob '4^ Hi*!!: •.rrro'^a -:•♦ it» -y ■ t ’.i ^ r: : yi ■ ‘ .iftor /io:fniirtj i.-''Xp'5rti4'tP- ’ -■ L-OS < ti I • » . .1 i. \ i :• ;;i*c.r ; y.X ■■jf ^ ,:.:* c.;i - t » r • ' 'jJ ■ ■ , :^c;i. t « 4 J. t ^4 • j • : ' 1 - . ' - •CJ. A /i ; 67 iJ’ig. 9 ~ Luhrig Fine Coal Jig 60 range of sizes of particles in the raw coal being washed vms too great the fine refuse and the coarse coal particles would not be separated. In the Luhrig system the principle of sizing before washing was carried to the extreme, on the theory that the more nearly of a uniform size the particles in the raw coal are made the more complete will be the separation. The extreme length to which this principle was carried out in the early Luhrig washers is illustrated by a large plant erected in 1880 at Reimsdorf Colliery near Zwickau, Saxony. In this plant, as described by Stutz, the raw coal was separated into nine sizes, and each size washed separately, the five largest sizes on Liihrig nut coal jigs and the four fine sizes on fine coal jigs with feldspar beds. TABLE 5 Sizes of Raw Coal Treated At the Reimsdorf Washer Product Number Size Millimeters Equivalent Size in Inches 1 60 to 70 2 3/8 to 2 3/4 2 45 to 60 1 25/32 to 2 3 30 to 45 1 3/16 to 1 25/32 4 15 to 30 19/32 to 1 3/16 5 8 to 15 5/16 to 19/32 6 7 to 8 9/32 to 5/I6 7 5 to 7 3/16 to 9/32 8 2. 5 to 5 3/32 to 3/16 9 0 to 2. 5 0 to 3/32 16. E arly Development of Coal Y/ashing ^ America. The first record of any activity in America in the way of coal washing was the granting of patent No. 20756 to Hezekiah Bradford of Reading, Pennsylvania, for an "Automatic Coal Jig” called the Bradford jig. 30.*: ' ili' .vi'i'a;'! .'X -'.rue:- J B:ri r»i ? • ri 'to ae \q m ’■; • ' — r^on 'joIox'J ^' O' 1m>co -> 'j..«'.o wi'v r':-' ■^sry't'n: 5ri*t 9 ^'i' “•x^j ^i-<■ .* ■ .^ ' '• . *:JiJ I w ^fT:.:tfJ: -'./J nl . , •':•♦,*•.; ^ li' '.^; i"i ‘n Ijtoo '>• T •■! - rx - t )‘Z}i i ’• J ? :. i -^XiJin • ; ,r .'t fKf u ..r Qf fWr,'.*''k ■ "IT ^’C-.'.r :: V■. '".' w. *.▼£« f{' . o , r , -ui-i ■•'> li . '■ ' -c’ ■ 3 ^cJL'i nrl rro-i' r- \ . icjo ..■«., - .... . . . ~ , ; i.nq,^.?»X 3 'i “Ir t ti ;yr. X oJ . tKi '■-J'-.v’X 0 ’ ■■xy 0 ^ ' :'v^ oj <->: <*t ■: 0.* • a i-WV • i iOO 'l : ;.;XL ’ i 'i < • ’* * iii 2 \:. V • . ' r I.' r X \\viS X t X. ''•• ; ; i“j 0 .j cv Cr s'' OJ 1 V •x\. 5^ y ->>■■ C •» f ‘ ' { T \ 3 • :i'v 5 • „ ..% .. . 71 r: *' ‘ ^ » • 0 > O.t 3 Q -«■ S/ :-2 1 Vi *....’ X'oo "i j •{: -?.• ■' •f -J ax *:.^ ' ■'. fxx ' . ^ r 4 vrt 'X. OJ * ’ V-.* • ..-1 OXi i. ' o v/ x> X •/ ' • J «.ji t ** . . ' *r 69 There is no record of this jig being used in coramercial practice, however, until years later, about 1880, when an improved Bradford jig was used in several anthracite washeries* The first actual coal washing operation^ in America was probably in the Pittsburg dis- trict of Pennsylvania where Jones and Laughlin had trough washers in operation for some years prior to 1870. The first jig washer^ of which any record is available was erected in 1869 at Alpsville, Pennsylvania, about twenty-four miles from Pittsburg. This was a small plant with a capacity of about ten tons per hour intended to be used for washing coking slack from a group of nearby mines. It was erected by a German engineer named John J. Endres, vfho had been employed on similar work at the Prus- sian Government mines. H. H. Stoek^ gives the date of the beginning of anthracite v/ashing in America as 187 5, with the introduction of jigs by the Lehigh Coal and Navigation Company. In 1870^^ samples of coal from along the Pittsburgh Railway in the Standard field of Illinois were taken to Cologne, Germany, and subjected to extensive washing tests v/ith an Osterspey jig. The results secured were as follows; Ash % Sulfur fo Raw nut coal. 15. 57 2.99 7/ashed coal 6.00 1.40 Coke from washed coal 10.00 1.02 Yield of washed coal 60^ to 65^ of the raw coal. ^TAIKE, Vol. 3, p. 77, Discussion. ^Process of Washing Coal, S. Deischer Proc. Eng. Soc. W. Pa. 23-202, May 21, 1907. ^Editorial in Mines and Minerals, Vol. 26, p. 478. ^Coal Washing in Illinois,. E. E. Meier, E. & M. J. 22-88. f N. t < ' 1 / ■A • K 70 These results were secured by very close sizing and re- washing the washed coal. Following these tests an Osterspey jig washer was erected in East St. Louis in 1870-1871 for Adolphus Meier & Company to wash coal for coking. The Osterspey jig was very simi- lar to the Hartz jig from which the Luhrig jig was developed, except that it was provided with a differential motion to give a quick down stroke and a slow up stroke to the piston. During 1871 and 1872 Endres erected five more piston jig washeries, all for washing coal to he coked in a new patented form of bee hive oven called the Belgian oven, vrhich was being v/idely introduced at that time, with the expectation that it would make possible the production of good coke froin the low grade non-coking coals of the Middle West. One of these washeries was built at Eliza furnaces, Pittsburgli, Pennsylvania, one at Hollidayburg, Pennsylvania, one at Irondale, Ohio, one at Equality, Illinois, and one at Joliet, Illinois. During the same period a Berard washer^ was erected at the coke plant of the Johnstown Iron Works at Johnstown, Pennsylvania, for washing coking coal, and in 1873 another of the same type was put up in the Broadtop Region^ of Pennsylvania by the Kemble Coal and Iron Company for v/ashing coal from the Kelly seom. This period of washery building in the East and Middle V/est was brougjit to a close and operation of most of the early washers v/ere suspended dur- ing the panic from 1873 to 1879, during which time the best Connels- ville coke sold on the market for ninety cents per ton. ^TAIME, May 1872, p. 223, Discussion by M. Pechin. ^Coal Washing, J. Fulton, T. A. I. M. E. , Vol 3, p. 72. -o_.. : '■■uu.'X. ;■ 1 i* ■• - c ■ 71 In 1875 the practice of washing coal was introduced into the Southern field with the construction by the Eureka Coal and Iron Company at Helena, Alabama, of a Stutz Jig washer to wash coal for coking in thirty Belgian ovens,^ This washer is said to have been successful and was dismantled only on account of the abandonment of the mine. Due to the hi,^ ash in the Alabama coals, which are other wise good coking coals, washing has been very widely adopted in this field. In 1904 there were thirty- three washers in operation in the state with a total capacity of 26,000 tons per day. With the return of prosperous conditions in 1879 a second period of washery building v/as initiated in the Eastern and Kiddle Western fields which has continued down to the present time. Be- fore 1885 five more washers were erected in Illinois for washing coal for coking, but none were successful in reducing the sulfur suf- ficiently to produce a good metallurgical coke and all the washers built in Illinois since 1885 have been for the purpose of washing coal for fuel up until the summer of 1918 when an extensive washing plant was erected by the United States Fuel Company at tiie Middle- fork mine at Benton, Illinois, for washing coal to be used for cok- ing, mixed with a large proportion of West Virginia and Kentucky coking coals. The first washer erected in the Rocky Mountain dis-,trict was a Stutz jig washer of the Colorado Coal and Iron Company at El More, built in 1881 to wash the Engleville coal. After several years operation this washer was abandoned because the waste in the refuse ^Coal Washing in Alabama, Ramsey & Bowram, Mines and Min- erals, Dec. 1904. V I 72 was excessive and a coke of 10 per cent ash could not be secured. In 1893 the Colorado Fuel and Iron Company conducted tests on this coal at the Luhrig washery of the Sloss Coal and Iron Company at Birmingham, Alabama, but the results were disappointing due to the hi^ proportion of bone coal. An experimental Campbell table washer was then installed and operated for several months and was found to do good work, but at too small a capacity, A Forrester jig was then installed in the experimental washer and tests were made with such success that a Forrester washer was erected at Sopris in 1896, The first Luhrig washer in America was erected at Birming- ham in 1890, and in the ten years following six other washers using the Luhrig system were erected in ^erica at Carterville, Illinois; Belt, Montana; Be Soto, Illinois; Dunsmuir, Vancouver; and two near Greensburg, Pennsylvania. These washers, however, were not very successful in America due to the difficulty of operating such a com- plicated plant with the unskilled help usually available here. A wide spread prejudice against the practice of washing coal in gen- eral, which grew up during this period and remains more or less to the present time, was engendered very largely by the great diffi- I culties and losses encountered in operating the ea.rly Luhrig plants in which the principle of close sizing was carried to a ridiculous extreme. The great number of screens, classifiers, elevators, con- veyors, bins and jigs necessary in order to handle the various sizes separately necessitated a large capital expenditure and, in an attempt to economize, the individual machines were usually made too small and were crowded together in light wooden buildings three or four stories hi^, so that the plant presented the appearance of an intricate maze of elevators, conveyors, belts and shafting, whicl: '■ * ' ( I OO V ' ‘ • 'J'' cC.' '.i I r ‘v Xi.’ c )J cu*j «itJ .1 ^:, ir V ; 1 ' . % 'c; OT. ~ii.\ : } ^ ■ 7 ' ^ 9ti$ ^ — ; • ■ i ;»■ i • ' '■ '■ ■ : ■' i> 1 : f 1 - • . . -,.'1 on^ . = , ^ .licrx: n . • >o t» to.ioiq .r. : ~o: Ao^c -.■'f-: — A-f.-;; - : : rj , ^ i v.iv*,iA ooj ^ v "* , c *1 -I V' Gj ' t > r- VI" M-T'Itj- liTi.-fj. ; -.i.' ■■ k. V J V » . V O 73 furnished numerous opportunities for disagreeable break-downs* The complication of design was further added to by the machinery manu- facturing companies who built the plants, as they v/ere naturally desirous of disposing of as much of their machinery as possible. \7hile the Luhrig nut coal and fine coal jigs or similar machines are still the most commonly used form of coal washer the complicated Luhrig type of washing plant has gone out of use. It has been found that the laborious separation of the coal into eiglit or ten sizes is unnecessary and undesirable. The most common prac- tice at modern -American washers for coking coal is to screen the .raw coal into only two sizes, or at most three sizes before washing, and at many washers preparing coal for fuel screenings ranging from three inches in size to dust are washed together in one jig v;ith satisfactory results. m.n fi-, f, ‘ ’ ^ ' I • • . . ^ \ ' • nt-jr*o .tJ I'O - - ’ .-.'L-rco 1^,'.'} 'i.i •is I t Cn: L 1. ‘ .'■ I 19 «■• i 2. . . tc £-Ci*riec ■0:iX •■ ’■■'.i -‘''.-w oi.r- l^adlfpT’ rt?oo' r, ismoir.' . .. i 'U .u;. ‘vX'i-v'hr r. ' .v' ;:I r*iv' • -'* < .irrcibo;j. o;,: a ■5 ' ' CF^‘ wx,;ri lAoo •<’' ■ 1;' r^ri^ 74 - chapter V MODERH COAL WASHIHG MACHIHSRY ^7. Jig3 . Althou^ a number of new developments in coal I Y/ashing machinery have been introduced in recent years, the jig, in one form or another, still remains by far the most coimnonly used form of coal v/aslier and will probably continue to be because it is the only method which has proven entirely successful for v/ashing coal of the fuel sizes. It is safe to say that, in America at least, more coal is washed on jigs than on all other kinds of washers combined. The fine size to v;hich coal has to be crushed for treatment on concen- trating tables eliminates these machines from consideration for washing coal for fuel except as auxiliary equipment for cleaning the fines. PRINCIPLES OP JIGGING The jig is esseni tally a perforated plate or screen sup- ported in a horizontal position with an intermittent pulsating cur- rent of water flowing through it. On the downward stroke of the plunger, the water is forced upward tlirough the screen to a height of from six to twelve inches above tiie screen. On the upstroke of the piston this water flows back through the screen by gravity or is drawn down by the suction of the piston. This cycle is completed from eighty to one hundred fiftj^ times per minute depending on the size of coal being treated. .. • : o*; Mvq 40 -! '' Joi '■ •' .nov'it-in , f-.ii' L*:- 1 -j ■?»cir‘tol .^r(? - j 'XOw^ij'll jni •. *'*. 9^ . . " .rv'i .1 oiJi moil: . 2 c«; :■ Tlbno.. X^. ;' ^ 1 -• vv.,-»i. ‘?o:? - ' Ic .•■:L^ ^*i■/•:.'^’o^ '" . Sfiv‘ gniy :"• '.-L . , V \/*‘i -'-i. ’^'?v --•■•- ■' •' * ^ ..-.r.i . . i woi«.'-'T91 ai fTC 1 ; 2® S j ; s nc r'c-'*v--i-! Jj.'iisi'. ‘ ■'i' I 'l^f' ''lo*!; » t/loi ' ■ ; Tnoo ©*.;j — ' . • /'' •7 J ' ;- . 'j.w"' ,:o t'‘* :^;(o ■ . ;.,. ... 'i.jqx- "iv : i ', . T '* ^ , to noi.? 0^ ^niJfi. .. -.Irtt p_.il . -. jc' .:i , : V :»o tv '••I.T 3"* ic vroj. ' ^ .* .‘I: .. ■•* . r«» £3 >j D.-." .1 g„U CrClU , ov -'0 c-^- r i v: il: '**, o.^ . :‘ii vIIi;t«a9p-qro X;.o:) r .•...• ') . ■r*'. . iv.' ..jv.'T j: Iij;fJr)i. ^ c: * '"‘lx .• ' ' ' ^*;':v,’ - vX ‘"J -:^on w OcOit-iVd : .V. ^•-.' ■?•/■ J • I -ov.-v xv-roT*?- .,.i7Ai i.J- J“i>- ■ "'£ ■;.■> Ov 4 ■ri7 . J v-.t "‘'it ot I'-r. uq ;■ ; .'6 '>2Xf> •■i *c bou'i’ZMiiT * ^ *r <*.4 4 ■J r •. ■.• ■• •:-:v...H,{ It r>Xt'XXi •' I. ’..'rra « > . 1 * f' ’•> £ :;r nljiiltu * :■*: Oiilf * 4 i boiXjjp V: ’ n L} j. UOX •^ * • " • , ;■ e .it / ^ 0 *X .-J _L JU 0^‘7 . .'i'V j‘.;''. 3 X; 10 v-i ‘£t:' ViV^ *:■■. 3 ^xr.Xi tv - ^ r>*: V L'-i - .iO rri Xo rlor j oiX/?': .\x i;vOiX'0"t'r 2II ' X':drfe -to .' oli^n^^^oouz nX ofi? .BA. . t.-. Xuovi'i fi • , 6. • ; orfi vii>; x'f d' * ' 1 -rjoa ■•’-fj f?:liiaiO^ 76 Later investigators designated as “hindered settling” the fall of particles enmass under the conditions existing in actual jigging practice where the free fall of individual particles is hin- dered by immediate contact with other particles. The hindered set- tling ratio is, as demonstrated by commercial jigging practice, larger tha,n the free settling ratio of the same minerals. Professor Henry Louis^ explains this as due to the fact that the small parti- cles of the heavy mineral which, by the free settling ratio, would settle at the same rate as the larger particles of the lighter min- eral, being much smaller than the equal settling li^^t particles can slip throu^ the interstices between the large particles and may therefore settle with less interference. Professor R. H. Richards^ considers the falling of particles under hindered settling condi- tions as equivalent to free settling in a medium which is heavier than water as each individual particle must settle throu^ a medium made up of all the other particles suspended in water. A third idea advanced by Professor H. S. Munroe explains the large ratio of sizes th^ can be jigged as due to the effect of interstitial currents on the small particles. By experiments with particles falling through v/ater in glass tubes, Munroe came to the conclusion that the rate of fall in restricted channels was alto- gether different from free settling and obtained an experimental settling ratio of 1;30 for galena and quartz under these conditions as compared with 1:4 for free settling conditions by the Rittinger formula. Richards checked this value by dropping a mixture of ^The Dressing of Minerals. ^Text Book of Ore Dressing, p. 268. •f t' .1 anoij- ‘• •V •: > ,.t< OQiur.r.o e '* ,. ^.y; 1 1 j ' r>«r, - : • f v..i : . - - i: : • -ti. . v‘o--J;iao e*>.±, • :*.-v:J. vc! , t 'c:.+ •x.t.'jiiota»b ' , - >ini.L - . '■ ':-. :r f'-.r r ciJ * ;■ i ; - , * ^ XI ,^ •: . ‘; * ■} It n . a/:irXqxfli I 'v' X i':uo^ ivt ^7;;or' vj “tv '^rl' - ,i..' :. ■' o o.it 2^ ■*•• ai.i:.u .• .» ;a -)!>r*^se 1 f • !'o.'-^ *!..:•; J ... ii ;; layoff ’^rf* '.•/ t '^Xl-JBr J -’-a , 2^ •' r . ;,;i. ^ i- . C I ■* '’ cooiw*p*'. •< J ' ■. ' icjiatiC .-/.i'-i 1. r'-i' ► ' *” 'iO' .\iti;'i 4 ^T’' ^'tcJ ri «M£i '.'♦i'.v -- ■- - -.'4 w.;-£2'7.l2' ' f':^ :• aoXolv'nv; I-' - orj /a'u-jiii^irxoo i •.*" • -i:: • V rl gi-fx' *'*£;r ■'•• . it„.,'..:.vi.;/f ^ ;j- a^.'!-- P:i;i^'i.:i ; .,-.<-X''i ‘ o_ . t . ' v '• jisJ-i j\ ifi.tj . j : '^ '£' vv;’7 ni;r”j . .' •• -li ■ •,.-••'» "oiiic.'? lortxfo ! ' IX.'. . (ja .* 9 r ' i „ I . ’.r , . CC;', dO’t Oli vj O .' • ■ rTclViJS 2s6i ixi# i; r w X ■ . ■• •? : .'./I- I :i'i • ' Aj O*' - . 2 . I« ■-'.■£?? .TO *J 1 . :•* V.- :I,;;o;i •:?, v,i _.r. ! €:;tjil 0 J 17 .L,? -o. I ...V” £lo-:i'j. if'Ioi.'T.’ -O':, i ** to e^ 2 'i .: C :I ^ I -I — : ft '»«p.x'-I;o lirr;.,; i^rilJJ-r . oom 1 ■••'!: er;Oj. li:: : .o 700 , .■* 'ivL'ftr? ryoi: oJ' ,ri i.'/t OS:' ‘ .» oil i;cil r;.-.'- •iif .2 wii'- (.■•' iO r':;.:T '; CV ^ . J i yT‘ ^ _ *'■ i: » > V 2 '£ y* X ; . : i 7q O'f. - ',*,'1 n t : i . , •.' , ; .r ;\j h -. lotH ifi'-’ •fxi/ro'’: \ A liOqOTl . 'iO t Hgp aexiiBsttas-r^,-- . . ? ‘i , 4 f‘- f» f 77 small galena and quartz particles throu^ a slowly rising current of water in a device which he called the pointed tube. This had a narrov: section at the bottom. Screening tests were made on the ma- terial which settled throu^ this narrow portion of the tube into a rubber bulb below. The ratio of the average sizes of galena and quartz found together in the bulb was 1:6. The interstitial ratio for shale and coal if increased over the free settling ratio in the same proportion would be 1:9 where the free settling ratio is 1:6. The effect of the interstitial currents is operative on the down-flow of the current as well as tlie up- flow and where suc- tion is used drawing the water down through the bed by the return stroke of the piston a classification of the fine particles will be effected in the interstices of the bed of material on the screen. . This is born out in practice as it is a demonstrated fact that a A natural feed of unsized coal is washed more effectively on a jig in which moderate suction is used, than on one vhich is especially de- signed with valves in the piston or a differential piston actuating mechanism to eliminate suction. On the other hand if closely sized coal is treated on a jig with suction on the return stroke of the piston, the tendency is for the particles to arrange themselves in reverse order from that desired. The coal particles being of small- er inertia than the refuse are more readily reversed in direction at the end of the up- stroke and are consequently drawn to the screen ahead of the refuse by the suction of the return stroke. In order to utilize the effect of interstitial currents in jigging closely sized fine coal a permanent artificial bed of coarse material is sometimes placed on the screen of the jig. This a-cts in the same manner as the shale bed accumulated in jigging an £ ‘ ^ ' ■• ^ .. ' r ■■ .;‘*i.- hfti. » ’ *■ I* ■'-.*■ tiX cr -1 ' :J ■■ 'rXiOv ' ■■' r'’r>ifit» ! 'y.Tjt?K "Xj ..- r.iq -.j «jt? J •; (!<■:!. - ;i : , ^»cin<;rt J oa ■ CaiteJ ‘■,. -■ ■'N;. •'• .r. • .*• ■■ . ; jLb ■ .iliid’ ■ r^rfirx C.-iJ; ; : - . : ;' \id o.^>l :i L 'UOi - 2J:.. .1 ‘•■>u O':’':" - / "tovo IJ; l3DS '*n :r o' ♦ . A a V .10 0 / •i \ii ni’r. >*t.‘f'. j !•: ■ V* t'T •• '■ ■ .'-..'i vj -I-, i •• :..v 7 ;-ti ..5 -'10 \ cwu / ■'<>;' i :,•< r.- 0 i:ui' ’’■.i: 0,.^ari n; r.ox.: 'v*-' '■••'-I: fiJ ': :;o.c £ n '■J::; i cj o.-C*; ; ■ r^c iiiv-j*.'! ;c fc'i ; (^(i. 1 -;■ ;. t oU* •' • : tti j'j'- - A> ri e no ••: -.•> i : .'■‘‘■'‘Is -- I V,.r ■ J.U ' 'J tr. : 0 .;:; , O r. •'..ci;s.‘...>'X"’'-’i ii' c ’j'OSXn *.X il ■’ r !^;r,<'i! 'I •<*.'. 9 f'* ;*■ . ‘'.o '* : ofiJ ao i . i 2 •-" .rJt;- . - ; L'C i ai , ^,r ai rJ-'-'i'^nom rfojtxX'’ .• .' Xoi-- aJ:'cG~T.:v ♦ ; ...j 'nia>?rfo '.■ ...... ■•■'J f •.; n I f. nu ■ :L . •; . - v:;- 1 fe.'* ^ i*: OJ . . ‘ui lo') -,'i vy^j-arte '*' I’.'O , fX ■•,' ij i ni-. ' tidily/ ■5:; 1. .300 srH .♦>' *fi 1'=}^; *,: *.'1 0““»V0'i iiy.; X ri* 3 '..J;'j ri h>i ':£j:' cy'C oaoci e'l.a oajJ'i -•■- ? i* . rf.'i: •i-t's'rai a: • - .- ■] ‘ . ••; i 3 : arit ncif oi/:{ ®Jut '.„j •s:’ no'i'H/y ri .: .? r.-; . -i 'i.; .ry?- To Cli:* TxiLldi/ t-c^hiv ,al '-Q 1 .iJ':a y. . 'i «. f -.co a fi . ijor.ia ^IbsoIc ' i:v, - '. ril ; . ■ cr > ' "iy I’c .•*:l''j r a. j ..'■•■ a-Xq ri X».i'..'’: ■ o^'Xr.oo ’ .:.;• .* XLr'rif.oo«'i 3 -X '.>X#!V.s Oiii '. 1 . '•fortaa: . ~ oa.‘ ri''_ 78 unsized feed. The fine refuse is drawn throu^ the interstices of the bed into the lower part of the jig called the hutch. The mater- ial used for a bed is usually crushed feldspar having a specific gravity of 2,6 or about the same as shale. This method was intro- duced with the Luhrig system in 187 5 and is vridely used at the pres- ent time for fine coal jigging. During recent years great progress has been made in jig- ging practice from the viewpoint of capacity and economy of opera- tion, Very large plunger jigs of sixty to seventy-five tons per hour capacity are now used successfully and the cost of jigging coal has been reduced in well managed plants to very low figures. The main features of jig design a,nd operation remain practically the same as at the first American plants built in 1870 and probably nothing in the way of an improvement has been added which apprecia- bly increases the effectiveness of the operation so far as cleaning the coal is concerned. JIGS IN PRESEL^T USE Generally speaking, the piston jigs in present use are similar to the Luhrig jigs already described. The mechanical dif- ferences in the various makes are usually in the method of piston operation or of refuse discharge. The Lehi^, Forrester, Foust, Shepard and Coppee jigs are operated like the Luhrig by a simple eccentric motion which gives equal up and dov/n movements of the piston. The Elmore or New Centui^' jig and the Baum jig aim to pro- and slow up- stroke duce a quick down-s troke^ to reduce the effect of suction in the jigging compartment on the return stroke. In the Elmore jig, this is accomplished by means of a cam on the eccentric and a strong spring ?. 1 £> .r I & oe-iij •' ' - N' CO .' r » f ' ^ . I ' 0 ' a a; t e. 'rfsac'iaV L.' ^ ■t: i V i l‘TiI .,0 j. U Jir ■ toa^i - .V* i XG: . , 1 - 'r r ai hoc sni t : X/.I .>C. ''.r .-L' . .C'O' '■ ■ / ■ -.'OA H . -J lY'Z' •: *;. rto.t-:r.; ©rfJ u'cTlW . ■’ 'A* I o' XI i.o^sf fiAi'j ^ -i«o\ :u..'rr/r — ■ ■ * . ^ ' :c» xpf}‘\ooe b,’ . 'jlo>*q^^o t ^ ■},•:. -,tv t'i ol evl’t-x-^a- ■ :' 0 ^ V v i i^ T*:_; -a':*: ■ •:'i >.' • '•''^- ' - '* V L ' - ' •'»■.' i'u.^tf VO oi:.‘ i o‘jof"'o -■-ir xcr v;*c '■•’'■ ■ . ,' .j ,!.-jr^or.1 Oi'-i . 1 ',«mTb '.?B,C/ 0‘iSj ^r^^i,-., 1 n; ■ O.l "}. tiT* '^r*‘ i Ba Oils*! * o'i-- '.'' , . : ' ;T . V f» 8 A;‘iox Iz^ v •' . .':. .-p M ‘♦.u 9Ali 'ooj Ti-}. ' i t '>‘v‘;.toO or-: -Ci r.v- ^ ;,r: o;ia qi.* I.vpo {oiiiw iUUJOiu i * ac- ( -> 0 ,' \;;xirfr,?>: •• • - 'J'tawix. : 9 o r 79 v;hich makes the rider follovr the ccm closely. In the Eaum jig com- pressed air is used to produce the pulsation of the v/ater in the jigging compartment. Probably the newest jig of this class is the Pittsburg piston jig used at the Middlefork vrashery of the United States Sted. Company at Benton, Illinois. In this jig the piston is horizontal and double acting, working in a vertical partition below the middle of the jigging compartment. The effect of this is to give an up- wart current in one-half of the jigging compartment cind a downward current in the other half. Any of the piston jigs may be and are used v/ith artifi- cial beds of feldspar for fine coal treatment as in the Luhrig fine - coal jigs. The most v/idely used of the movable sieve jigs are the Stewart, Shannon, iiraerican and the original Pittsburg jig* The Stewart jig is commonly used at Illinois washers. The characteris- tic feature of this jig is the basket or box with perforated bottom into v/hich the material to be washed is fed and over which the cur- rent of water carries it. The entire box is suspended in a tank of water from eccentric suspension rods, which impa.rt to it an upward and downward movement. This forces the vrater alternately bs-ck and forth through the perforated bottom, lifting the coal and allowing it to be carried away by the stream of vmter flowing from the top, while the heavier material or refuse settles on the screen plate, from which it works forward and off into the water tank through a valve set at suitable height. The Pittsburgh pan jig differs from the Stewart in Uiat instead of eccentrics a crank arm mechanism is used in order to 80 produce a quick dov/n-stroke with a slow up-stroke and suction in the hed is still further reduced by extending the sides of the pan belov/ the screen and inserting a solid bottom with valves which open upward, but close on down stroke preventing the water in the pan from rushing out through the screen. The movable sieve jigs are most suitable for coarse coal and for the production of two products only, as in order to produce a third or middling product two jigs v^culd have to be used. Por these reasons their use is confined largely to the washing of coal for fuel where a large tonnage of unsized coal is to be cleaned of only the large pieces of clean refuse; although v/hen the Stewart jigs were first introduced a large number of these v/asheries were built in the south for v;ashing coking coals, A number of the jigs described are illustrated in Pig. lof and classified as to method of operation in Table 6. ^Prom the files of the Department of Mining Engineering, University of Illinois. . . 7~ \ .. . v; 4 hoot-; M K «k .V . - Sj'^yo X!-t3 o ‘.' ^ '. t lie ',' , r.:( C:; o. ‘^V i cJ- -X'^6i-o n.*- t . ; . ; . vj Xq {•> .1 c . '-' i J DU'. O t.i J . • i V.- 4.. .. . j . .1 1 (jwj V -..n. Jt*“ ■Sj 1 ' ‘ - - i. -j '. . / . 05 (fiJ J- . . "f* j : , ■ ■ ii ■ «104 ./ >* . vf fJU I'i , t . , ■« .' ", -. 'to i'f.Ol'J - « ' t ■ ' : -. v.Jcr> \. 1 .•• .iV •ir. ; .'CJuor ‘ 4.'..’j ■ ■ r ^>9 J ^ . ' f.i, '*r W • *•' * '’ 4 ' , •; . ,• i .-.•1 _ c ‘ 0 ^ai;. I .. ‘i f’L'^ 0 ‘-'J. • ' T'^ii.. i If; , '.•.w 1( 4 81 Elliot Trough Y/aslier Stewart Jig i^’ig, 10 - Types of Washers in Present Use •S. ' - y» . ^ r ~ : ‘ ■; * ’ I • 1 ,'yv, -i M , « ^1p i * ', ‘ • .f.* ^ ,,>y i ♦ ^ /• •V,T ^ ' •< . •» * •► ■ V A - V ' '• ’v^"' -. . V *1. ,^-' * K*>*‘‘ *./ -n 1 ''"T . 1 » • • **M - meiti 1 “ •: .. J - 82 TABLE 6 Classification of Coal Jigs Cha-racteristic Features Piston Jigs Pan Jigs Equa.1 pulsion and suction strokes. Luhrig Piescher Coppee Forrester Foust Shepard Leh i gh ( an thrac i t e ) Pittsburgh Elmore 600A Stewart America,n Shannon Simplex (anthracite) Christ Suction reduced by differential piston or pan motion. Elmore 500 Elmore 600 Elmore 800 Humboldt As terspey Pittsburg Suction reduced by valves. Hoyle Montgomery Elmore Pittsburgh ( Shannon^ ( Stewart^ Pulsion only pro- duced by compressed air. Baum 18. Trougji Washers . The old hand cleaned trou^ washers which were so widely used in the coal fields of England and Scot- land up to about 1890 are now entirely obsolete, althou^ up till very recently some of the improved traveling riffle type were still in use in Scotland. The most common of these was the Elliot washer in which riffles were carried on a traveling endless chain which ^Shannon and Stewart jigs are made both with and without an auxiliary bottom, containing flat valves, below the screen. , m -. AMt uW 83 moves the riffles slowly up the inclined trough and dumps the ref- use over the upper end. This washer is similar in operation to an inclined drag conveyor-elevator. The Scaife washer manufactured in Pittsburgh, Pennsylvania, was a trou^ semicircular in cross-section through which the coal was flushed by a stream of water and kept agitated by rocking arms. The refuse was retained behind semi-cir- cular iron riffles and was discharged by dumping the hinged bottom of the trough at intervals. A revivial of interest in the trou^ washer is reported in Belgitim with the introduction of a new modification called the Hheolaveur. This is essentis-lly a rising current classifier attach- ed beneath the trough and communicating with the refuse slots or the pockets behind the riffles in which the refuse is collected. The Rheolaveur is an inverted pyramidal cast iron box which fits on the bottom of the trou^. In the hopper bottom is a spigot for drawing off the refuse and a water inlet pipe to produce a rising current in the slot which assists in assorting the particles dropping out of the coal stream. The Rheolaveurs are placed at intervals of a- bout .ten feet along the trou^ and those which draw middlings are, in some cases, discharged into another trou^ for rew^ashing. At the St. Nicholas pit of Societe Des Charbonnages de L*Esperance et Bonne Fortune near Liege, Belgium, Coppee jigs were abandoned because of the hi^^ loss of coal in the refuse and Rheolaveur trou^ washers have been installed. The advantages claimed are cheaper operation, no moving parts, small floor space and head room required, and sim- plicity of operation. Results secured at the St. Nicholas plant referred to above are reported as follows;- j. r-jLO'iS : \ i * xu‘ etiff jovCai •... l .C-no erf^ '^' vo o«i/ I ill o'< r .'.t:j •- I - -i?-' :v. - lox^vnoo bvf.’ilt'rr; "•.L* O ' ";J: 'r..^ loX: u=»:; >'0' .i S , ‘ v, jfi , :.MU4/dlr i ’ [■ 'V.' *r 'J X. *. o-^:; G 'C boHo-'X'i 2'ir X.go:) .oiXvr - ' ‘ -Inp:i Xfti. ':*J o©aii.‘ ■*I i5_ \'y ■'airXm 9.*< , x- ' , ^^.o o i ‘■)'»% tX t.;l' 7’f3 -■ ,■ .:: " nav? jbiii7 aaXltX'i sio'xl iulcro ' JSuJ’*: oqo'i etl ■ ^a> •ir-k x;v ? ' 'Xi ©r r • v'srX ;! *jr J .y lil ;tan'; t lo fr Xv -v’^n. A ’• ' r>: .4 '■•' «1 1 ax>.tJ Gv/ ' ' '. • Iv GviXo^bciJ” r X ofi; X'v’ rt'i^Xotl 7 •* . "C X i. *v F. X-.. ry ;> 1 J r- . 0 : . xX-' f#Xrac'-.inc g 1 eiii"’ . -JovoI •£.: '.' ’ ‘ r*-'. ■ ; ■J' ^ •.it r=Gi.f./.GTuCO i fi'U’C'tj’ 5 *:^ Xfa4B9i1l>cf ^ • '■'-DO*. )o ni iv'‘X (j 1 9.;^ ' Jbfrlrieo' 0 ; tt ».,v 0:fJ :io ibir^" . 10 .^ *!o-.X Jcflo li,'' j r: o- '■'‘ft •.i . ■.T-; ...■' i 'j -j 1 mc.^.)o;f isqqorf j.(j r-J . ■ o*r^ .vc.*-*- vH-. - .Lr.l': -I *ju.. .'OT:’ s? "4i'^ J 0 /..J a iJ'tfl .• -. '.01 erij-ilo X»fG ’, J.q- 0 -ra 4 ; . iJ*roG4^ ft! eJsi^-.la W ; -. :» nl iv':''" • i J . ;oo.jX< «.•: ."'firav 'i oo.f-: • , '■..-->1^00 *lo , ■-.'.•.'I*' rivlilv G-ac; -' j; oaoqoD , -■Jijc ' --i xl onif ^*xo'? "'ic'.ij " r' ijO'xJ -rjifiv •4x 0 .0 :p o.i.'\ rx QAi ‘:1 I *700 lo cvioX .aoi^ .'l-vqc -t:.::- Dx:a )v-t:x.vry ^4cni n^o:i ev<^ = - -•■*,■ , 'jd'iiapo't noo*x ' '.'Gj.qti *icoX1 XIat‘ , ' jjniroa o.-* •-" , - ...ui..b,i:>';o 'to . . yj -T'c j;ulq G.-^Xorb' . Q.ii* i'.xjoosr a/'.: /fGG': . -; ^yX.r. -j/i. ' bs i) yi.. ^rotf-e 84 Per cent Ash Raw coa 1. . . . 26.0 Washed coal from first trough 7,3 Washed coal from second trough 10,2 Refuse first trough, first and second orifices 71,8 Third orifice 34,9 Second trou^, first orifice 68,8 Third orifice, final middling. 31,8 19, Concentrating Tables . Within recent years reciprocat- ing tables of the Wilfley type have been adapted to the concentra- tion of small coal and installations of such tables have been made at a few American washers. The V/ilfley table is manufactured by the Mine and Smelter Supply Company of Denver, The machine con- structed for coal w^ashing is called the Massco table. All the manu- facturers of concentrating tables have now adapted their machines to the treatment of fine coal and are manufacturing tables especial- ly designed for coal washing. Fig. 11 shows the small size Plato coal washing table which is manufactured by the Deister Machine Company at Fort Wayne, Indiana, The underconstruction of this table is shown in Fig, 12, The commercial size table is fourteen feet long by six feet wide. Fig. 13 shows a Deister Overstrom coal washing table in operation at the testing plant of the Deister Concentrator Company in Fort Wayne, | The Butchart table and the Overstrom-Universal table have also been used, at least experimentally, for the purification of fine coal and •with a fair degree of success. These tables are all very much alike in principle, A concentrating tabled as used in coal washing consists essentially of a linoleimi covered plane surface, or deck, approxi- ^Coal Washing, Horatio C« Ray, Coal Industry, Nov., 1919, 05 The Laboratory Size Plato Coal Washing Table 86 12- Underconstruction of tiie Plato Table ^H.I, I >» J WI , o a-'-g-i ce imj n .ow 'i »n . -wotiHritHp! kl • ’ 88 mately the shape of a parellelogram, transversely inclined, and re- ciprocated 230 to 270 times a minute hy a head motion mechanism. This deck is supported by means of toggles, or slides, on a tilting frame, which allows the transverse inclination to be readily chang- ed* On the top are tacked wooden cleats, or riffles, which taper vertically from the head motion end, where they have a thickness of about one-half inch, to a feather edge at the '‘refuse discharge end”. The riffles are about one-fourth inch wide set about one and one- fourth inches apart, althou^ this varies somewhat according to the material treated. Their operation is as follows: The raw coal, previously mixed with about twice its wei^^t of water, is delivered to the feed box in the upper corner at the head motion end of the deck, and thence throu^ a series of small holes onto the deck. Water dis- tributing boards are provided and attached to the same side of the deck as the feed box in order to obtain a nice adjustment in the I distribution of water over the deck surface. A slight side inclina- tion at ri^t angles to the line of reciprocation, and )idiich is ad- justable in order to meet changing conditions, permits the clean coal to be washed down over the long edge of the table into a trough or launder, while the action of the head motion in reciprocating the deck, drives the sulphur and refuse, which stratify next to the sur- face of the table deck in accordance with their greater specific gravity, out and over the short edge, or refuse end of the table, where it is caught in launders and conveyed to the refuse dump. The v^ooden riffles on the surface of the deck aid in the collecting and guiding the refuse to its proper point of discharge from the table, and also prevent the finer particles from washing over with the fr- . ; ' r? '. 0 ' I ■ V" 3 v.’v;XIa . -■ 10 ^ - - , ' -.iu '■ -j f • T ‘ ■ - i: J!>ii io; *w a •X * : •-.‘•XO nt ■- _J i. ^ X ■t J U "X V - ' ■ ' : ; r . _i . r , '>■- ■> '!.■- ■: 1 ■ : j^Uti.l : ‘ ^ ^ " 'Is . • ;) •: • j 'V' •’ ; ^ ^ ■ ' -' v'ii^ tt'r-; L -''c ■ - ' ■■;■;■■. iC^V' 'C r f;.- * /I j i.". 0 '> •.'T i i ') • c tj* I ' »■> 4 - ♦ \ *• * V J. - ')VX 7 , ’V-sC |T i , ^0 ; "" , 'iv.ij; :..i i •’- ■■ -J •'• .:i biixs i ^n.' 1 • ■■ ’ • ■; 1 : *:i . 89 clean coal. The coal washing tables are very similar to the ore ta- bles. The principal changes which were made in order to use them for coal washing being in the riffling, which generally is deeper on the coal washing tables although so many kinds of riffles have been used in experimental v;ork v/ith the various tables that a gen- eralization is uncertain. The Deister-Overstrom table is made larger for coal washing, being seven feet wide by sixteen feet long, as compared with six feet wide by fourteen feet long for the ore table. The first use of concentrating tables on a commercial scale was at the Stag Canon plant of the Phelps Dodge Corporation at Dawson, Nev/ Mexico. A Wilfley sand table was installed there in 1906^ and used for some time as an experim^ent, but was abandoned be- cause of its small capacity. In 1911 further experimental v/ork was done with the larger Massco table and an installation of twenty- four tables was made. Since that time practically all the differ- ent tables made have been tried there including the Dutchart, Plato, Deister-Overstrom and Overs trom-Universal. In 1917 there were fif- teen tables of all makes in operation there, mostly Deister-Over- strom, as this table was preferred there at that time because of the hi^ capacity secured by the large diagonal deck. In 1919 an Overstrom-Universal table was installed for experimental purposes end the following results were secured in a test ruri2. •^Personal communication from Mr. J. B. Morrow, formerly Supt. Coke Department, Phelps Dodge Corporation, Stag Canon Branch. ^Coal Washing with Concentrating Tables, J. B. Morrow, Coal Age, Sept. 25, 1919. liu a-rc ot ii i I. . pvn ^,* o'.-!'j c.' ox ®h -wi rf' j . ■ i it.R/1 o 1*5 -• •-• •yo^oah »i ,- 'xX^liT c*d: oi ?tuiO’J : i lXax v x-vo . lot "v 77 Xi' 7 u aX>ol:{ \r:'!.. ;i o'j rtqi'C' ’J..a '.: a--;x:- o‘/or'^..5 ^ #.^4 1 * «r* -i .j noii s . vifiU V fT- i3 5» I ,;oX jaa”! oc .•;.t:i.i{r> ebtw f oove 2 :,r:i ‘. j , ,'rii-iB ^ • :. vioo i : * 't^BT ^•to ^•^■‘ lo't jiool M<’ rl-l - -xkQ I'J ba'ij.ijroo e ^ ;| r: I r- JO ..: no 3 «Icr.-;x 'V arfT' j noiw ist'iqt oD o^uo ,' m .* ’■ ) J". j-i.f -;j.< I ••►■ f X • ;.' oi'Xo'^ -» - -> d'-tiJ* <'>.‘-Ci- *X-T 5S©.' >iU ,;-7 X -r^r^J-wi JLJLvX nl . Xiwjfc- XX^'jjb aix Xo o'i j 0 J -vJ-ia-rJ 1' .'toix wT. f. iXr.'.’.i n-ri i)o» .»I.x. .j vjueAZ a/'fX f(X* w, o- 'ii7 XX^ t a? t ' sr.XX . '-a;.t ««w, ^fuo'x ■ ' ^ 'Dtijd oiJ T ^X-^JfloiTi b.‘ asod ->vsrt aft-is a-«ld- * X.i» jt ' ■'•; - I - ' vr^^r nl . r anov i mi ai^tvO i-0f'S3 v. - «iX > - • iiaon :Toi".«5ta<[o rJ asy.^-: IXs *io a©Xo -X roa^ ^ * * / 7c XrjiX ^je jioxrv? hr>vio'lr'Tq er^w sld.ra , /O’x^ p. ■ .1 ei‘:.i I’i , XBr;c'7...X -. •’;.*: o ■ " v. x \;:tXo.7.q 'O ffJLsl.i f)-:J ■ urc^cu'Xuq noszX'iD^ix^ 7 . XI..,?« ox nX''\.X Xiic^ i'aviol -::riJ'aTejvO r O VisA •;:/'. *';s. rij tlXXuy''T; r.’oXXo'l '.iU bOji v^Ltar^v ,.VO'ii'X:> -.•j.r. ono*.-' »••--■ . '^ ■'■• • * ^ .-”.00 7 '- nol-t nointx;r."’C') f 7 oor."ie^*, lioioq'XOO -’-o-'T aqZtii' .iquB .i --«rl ..'ll ^ificrio:'' rfJitt' XaoO^ .ex ■ .vtiilaMtt »< »• * ■#] ?i :’fC'YA • •» :r ;.'v:'w o ■'■-■ i^- ■•:tc •. Cl ‘u?'- 91 The chief advantage of the concentrating table as a coal washer lies in the fact that the operation is fully visible at all times, is capable of very close adjustment and the separation of the products may be easily made at any point or as many points as desired by simply dividing the sheet of water and coal coining off around the discharging edges of the table, THE CAl^EELL WASHER The Campbell washer is a bumping table similar to the Gil- pin County bumping table developed in the early days of mining in Colorado for the concentration of gold ores. Ten of these tables are in use in Illinois at the No. 7 mine of the Big Muddy Coal and Iron Company at Herrin. Eig. 14 is a rough sketch showing the general features of the machines used at this washery. The tables, five feet long by two and one-half feet wide, are made of one inch oak plank on a 4” x 8” oak keel (a) and is supported in such a way that it can reciprocate longi tudinally. The bumper pulley (b) is driven at one hundred revolutions per min- ute giving the table a two and one-half inch stroke with a bump on the back stroke. When the cam (c) passes the keel (a) the spring ( d) jerks the table back bumping the keel against the pulley. The table is inclined slightly toward the washed coal launder. The coal, flushed onto the table, as shown, near the back or refuse discharge end, is carried forward by the flow of water and washed over the end of the table into the washed coal launder. The bed of coal, as it travels down the table, is agitated by the jerking motion and the heavy refuse collects on the bottom lodging behind transverse riffles (e), which are vertical on the back side and slope gently on the front side (toward the washed coal discharge rrj: 'iv i , jv.si ,. - ' ■ vr::u-2 «.!. „.-,xJr.Mgc .rf; ,0 nriJ '.■ .-.-, 2 ,;,V -.i-., ,.:: ; :'■■ T .-vtoq Tf. .■■>... vXloee »a v rf.-atbo^q 9;.- •■••■“** - '•'V;"‘- i -.itivlb v:£qal« ,rf b„x. . ■ *'* :f;.«i6 j.xj ,. „'kV .. lU » . STKT ' ■ X- 'ir aK-'B ,xiai ].,. iqnorf , 8J .;,..(te ■ .:X;-v ™«0 1 /r r -i-b: in ,v."b ■..:•• ■! a.'.‘ ni ^ -.qai., 9l,x;j 5^2,, „j ^ ncij Kuns.-noo '*v» cXjnolo^ '■ rfl SJO.-.I I jr." nl, ! 1 '_J cbXj‘:J ■,'../x jn ..^.j. ' xnaqaioO 'iinl ti^cl ^t-iniV •jir ,k_* 'tg onim -ml,.. n,ij iij (,iix Si/riwoiiB dOJfljiQ ffcucr; it b.j. o»j .. i-jot n»t ,v. L.Xjji srii .vTSiXijis’.'olr;* '! ( •) ■ .. i.o -X "^ « no )Ct;X,| jso n-.': i »no lo si_. ,oot. # . X«r.Xb2,-llancX 3 J x.-xqio.-., m.o •! l„u y.;,, , ;ono ni bsXioqqxya „x ^ -i:-: ... ..oxi.xovo, i,ei.nnr .no d.. ne . u! .•:XXno ,oq»rtB«w arfj o;rJ aXoaJ a:-! lo iae 9 rj loro bad^t, Ai ,i.a v.f f>o,*,:JX5,a .-'■dcj o,;a sXovinx ... j^-. •io'tod w;V f Eo.Mod n.;j no oiDo'/oo., 'c-. odi a,., api Joa- ? . • 'i.; .ioi, .; orfi? rro <■ ' =» r“->i - — ‘ «' ^ on’ioY£iu''T:i i* ‘.Il'ti: p:>,.. ■= . vXXn .s : 3 qoXp .4“' ..... The Campbell humping Table as used in Illinois sT’. V- '** *i^'^i.<*#Hffi . 'V' ,'-‘^4 -• • ■ -T • ..w: V.'^'^ ■■'■■.;■ '^■-- V < ■ . ''. '-till .i » ■ ., V 'TW ' ^ ■ . 4 ^ ■ : vV , v:-% ■n- c 9 i A '■ *' 1 *■ ^‘ ’ * 3 R . "' ' >'* jjHM . ., ’ *'^ ^'--1 .•■<: . . .1, >••. (■. ^ • , v_ , W** ■ .. A''; ‘ . ,J "■A'fy 40 » .' iBr'VK '’■ /■ >■ , ■ A'Tx ■ ■ ' '' . ik . t L‘ If- • "^ fv •_ 1 . ' I av-'* ’'’\ £. * ..A^, * ' ■ ' •' •.' / - 7 , ■'‘** 7 , w':’. ..*^, ■“ a »,’ ^ . i'A-' .’S ■-, *'"'■ ' S t ‘4 A 7 ' ' lit V* ,r '.■' lir -I’: ... ; A:*'" ••,■■' j,l‘ {‘-f /t*. V;t i * • r. ' *' !- 7 ' . . , 7 ... •■V .A'- ' . ' * '-/.' .S.^T 5 K ^C:'' -S. ■• .ir :-4 t»?' • ,, '-A !^-‘''v.v ;:/^ .V. ■'.*.v^ ‘ji ^’■ '-’■'■•'a * . . . 3 ■\r •■■*'" i 95 end). The bump which the table receives on the return stroke works the refuse back against the inclination of the table so that it is eventually discharged over the back end of the table into a refuse chute between the piers which support the bumping pulley. The efficient operation of this washer depends upon the adjustment of table slope, volume of water used, length of stroke and tension of the spring to such a condition that the heavy refuse will be worked toward the back of the table by the bump, while the lil^t coal will be carried forward by the flow of water. Campbell tables are used in America at the following plants^ for washing coking coal: Cambria Steel Co. Washery No. 1, Johnstown, Pa. , Erected 1905 Cambria Steel Co. Washery No. 2^, Johnstown, Pa*, Erected 1920 Lackawana Coal & Coke Co. , Wehrura, P&. , Erected 1905 Dominion Iron & Steel Co. , Sydney, N. S. Erected 1905 Cascade Coal & Coke Co. , Tyler, Pa. , Erected 1906 Vinton Colliery Co. , Vintondale, Pa, , Erected 1907 Jefferson & Clearfield Coal & Iron Co. , Ernest, Pa. , * v. Erected 1908 100 tons per hour In addition to these plants for washing coking coal a number of ^Personal communication W, E. Winn, Heyl & Patterson, Inc. , Pittsburg, Pennsylvania. ^Now under construction. 36-12 ft, tables 200 tons per hour 36-12 ft. tables 200 tons per hour 56-9 ft, tables 235 tons per hour 48-9 ft. tables 200 tons per hour 36-9 ft, tables 150 tons per hour 24-9 ft. tables 100 tons per hour •J ’ •i^-v 'lo aciiT. ^ u ' . ■ ' c:j 4 . t ' f V ' .:-L > X washeries for preparing coal for fuel are in operation in America. This table is also used in Great Britian where it is called the Craig washer. 20, Classifier Washers . Washers of this type have a con- tinuous rising current of water vhich is strong enou^ to carry the coal particles up while the refuse settles against it. The Robinson washer consists of an inverted steel cone in- side of which are vertical arms and stirring plates revolved by gears. The bottom of the cone opens into a cylindrical refuse cham- ber vhich is closed above and below by slide valves operated 'by steam pistons. The rising current of water enters at the bottom of the cone throu{^ perforations in the top of an anular ring which sur- rounds the refuse chamber. The coal to be v/ashed is introduced at the center of the top of the cone. The material in the cone is kept in a continual state of agitation by the stirring arms and the ris- ing water current carries the li^t coal over the top of the cone, while the heavier refuse particles settle into the refuse chamber, the upper slide valve being kept open and the lower valve closed during washing, V/hen the refuse chamber is about full it is emptied by closing the upper valve momentarily and opening the lower valve. A photograph of a model Robinson washer in the Mining Laboratory of the University of Illinois is shown in Pig, 15, The Robinson wash- Fig. 15 - Model Robinson Washer, [ •rvr'strt'A ::i noii .'.’Xfic(o tj rr:v- X-oo ' *: : ..itarioijw Oi.'i h 9 ll 90 ci vi O'l&ctr rtX *iv»tr oci^ ■ d.Lrfi j bH , •r'.'iuiiW ^i«'. . . •- ry:^'L c :\^ 9idS to . : . •>' >3^5? ; I oaM *^T:*r :» oJ -^: ;>".o ^rrctJR ni tU>itt^ lo ^noiTeo nnjrcl**: arOi;G^:J , ^ J i/r^.- .f.V' O'.: co:ftt'T fjX-i-stVf ^:; ,-. 'jX '.- 4 'T X^o u. wD X^>o«o £>*>J'?''v: i as Ic w.''pia/too rroonXi'oJt e^n "li '-. ^vIcvj- j .'Ti'' -iX^fE: iii'L.-' ax'xx T^'V a‘:];ji /twIrJw ‘it t- *:> • _ ' £ ..oXr v.ilvo 4 . o^ri jaon arf* *.-*oi^u,‘ o ',■ .TSfjj-a 'i. jo c'-'X,:? 'c' V’OlstX Xii.-. <.'gd> cIj oi ;foXx^’ L: 1 -’ -'oJ^od oKX i.':o..'‘c. '. 'leJ c'-v To ^nc'in^ ' Sni . i-j'-^orr: ,aa.:;a'iq :j ifoi/'.r t;.X;r: ii>; 'i<:^ :■ U ni t.r'r/.t^eTC*lAt; - jv': -ano- ‘ ’'T.. o. ’ cit*' X nl feo'^c ; oX c.* Xaor- oout**:; o*'*'X nbai.-o'*; . v.TDO f»rCf ni X.- X':eX.‘ 5 iir ‘'av ►-aco o '‘X tr- co^ 0 * 1 ^ ir o*iv 4 .:*r .> X Xj;r: nnxviXX!, vifj v. : r ? J ^ :roo 4 ai af’j to s fV • ni iTHcdn fii aicnxXXI * 1 .^ • iiR^nvia^ &tf: L. ' 9 5 ers are ten and one-half feet in diameter and ten and one-half feet hi^ with a two foot discharge.^ The Howe cone washer is similar but shorter in proportion to its diameter and has horizontal instead of vertical stirrers. The Robinson washers were very widely used in the south at one time, but in the newer \vasheries have been largely supersed- ed by jigs. The following new installations of cone washers of this type are reported, however, in recent years. At five of the anthra- cite breakers of the Lehigh. Coal and Navigation Company cone v^ashers similar to the Howe are being used to wash No. 4 buckwheat in which the ash content is reduced from 30 to 35 per cent to 17 or 18 per cent. Previous to 1916, when this type of washer was introduced for anthracite preparation, the No. 1 buckwheat was the smallest size of anthracite washed. It is also reported that some experimental work is being done with the Robinson washer at the Stag Canon wash- ery of the Phelps Dodge Corporation. jijiother rising current classifier v/asher which is attract- ing considerable attention in Great Britain is called the Drapers washer. This is essentially a tubular classifier with a short in- verted cone in the upper part which serves to constrict the diame- ter of the classifier and produce a zone of maximum lifting effect v/hich separates the heavier particles of refuse from the coal. Re- sults of experimental work carried cut at the first plant erected at the Glamorgan Colliery Llev/ellyn are as follows; ^Lincoln, Coal Washing in Illinois, p. 25, Eng. Exp. Sta* Bull. 69. ^Coal Washing, Professor George Knox Proc. S. Wales Engi- neers, Vol, 34, No. 3. 013 '■>. '.'- I . . n" i: o.t . 0 - J lo 'M‘- \;t^v -. }■ ' ' ■:•• : ■■ 1 'o :yr^ n - R-i $ , •jri v,’0fT ' iiiMolli" , :t»o •fc’.iV ’vn^.o o ' -'.y', • o'J Ldn.l .. s , . ;i t>'... " •> -.J Uv 'C ■■.'■ • ■' 3C:j< : • J w nr. ; , . .. - WV . X ■ - , , ^ I • * ^ •*“ 'V '■ ■ • ■ o '! : • ^ ■ ■ • ^^t;o -- -V..' ... .. ■ 3 ;..:. ' 'j 'tc- . J: : ’3;o;’Jar!' . .'• .; 010 ' c. fJ o., . . • ,'j> 'C; V’ r ■ . I I X J- •>. ,4^ ■ ^ •■ .*. 0 : 'i.. .-f' ■ . '1m •vfC’ i . . . •* !■ • IJ W • 1,. n ;■;.■ .Jj i. OtlMijL* . l.-.kj TT*;. jc Results of Tests on the Draper Washer Material washed % Ash in raw coal % Ash in v/ashed coal % Ash in refuse Fine coal 31.0 5,7 71.2 H (1 22.7 4.1 73.2 Slurry l/S” to 0 size 23,7 2.2 70.6 « 1/8 « «« 0 '* 13.8 4,25 67.4 » l/8» « 0 ” 30.2 4,8 71.7 Samples of fine coal from a Southern Illinois mine were sent to England in the summer of 1919 for tests with this washer# The results secured v/ere no hetter than have "been secured "by jigging samples of the same coal# 21* Cleaning Coal by Oil Flotation # In the past few years some experimental v/'ork has been done with a view to the utilization of the flotation process for cleaning fine coal# This process as used for concentrating sulfide ores consists in agitating the finely crushed ore with water and a small percentage of oil, sometimes also with a small percentage of acid and accompanied by aeration# A froth, which floats the ore particles, forms on the surface and is skimmed off, Wcien applied to coal the refuse particles sink and the coal is taken up by the froth# Bacon and Hamor^ report the results of tests on coal washery refuse conducted by Dr. C# B. Carter at Mellon Institute, Pittsburg, Pennsylvania, Although successful in making a separation they conclude that this is net an economically feasible process at present, but ”it will undoubtedli'’ play a leading ^Problems in the utilization of fuels, Journal of the Society of Chem.ical Industry, June 30, 1919, N L 1 J . . ■‘i \ ! ^ n r . 4 • u ^1.' - . r (, I • . '.^r oltfi 97 role in meeting prominent fuel problems of the future”. They suc- ceeded in recovering 70 to 90 per cent of the combustible material in the feed as a fuel of 20 to 25 per cent ash. They report that pyrite floats readily with the coal but that it could probably be controlled by preferential flotation. Tests on raw coal have been carried out at the Seattle Station of the Bureau of Mines with similar results. The Minerals Separation Company of London, however, has introduced this process of coal washing on a commercial scale, and according to their re- ports wide plans are being made for its adoption both in Britain and in Continental Europe. At the annual December meeting of Minerals Separation Ltd. Mr. Francis L. Gibbs, chairman, outlined the plans for flotation plants as follows.^ Waste heaps and current v/aste from washer ies seem to be receiving the most attention. A pilot plant on a commercial scale has been erected at Aberman for experi- mental work on this material. Three commercial plants for treating such waste are in course of construction and various other accumu- lations are being examined. A plant for washing coking coal has been contracted for by the Skinningrove Iron Y/orks Company. A one hundred ton pilot plant is under construction at one of the Collier- ies in Prance, and plans are being made for plants in Spain, China, Brazil, South Africa, India and Japan. '/i' ^The Flotation Process, Colliery Guardian, Dec. 3, 1920. / 98 CHAPTER VI ItETHODS USED IN THE EXAMINATION OF WASHERS 22* St andard Me thod s. In ordinary practice the methods used to determine the character of work being done by a coal washer, consist of, first, the sampling and chemical analysis of the raw coal and the washer products; second, screening tests with analysis of the various sizes; and, third, sink and float tests on samples of the raw coal, washed coal and refuse. CHEMICAL ANALYSIS Analysis of the raw coal and the washed coal for ash and sulfur content shows the extent to which the impurities are being removed from the coal by washing. Where the proportions of washed coal and refuse cannot be determined by actual weights, the yield of washed coal secured and the percentage of the original raw coal rejected as refuse are sometimes calculated from the figures for ash content or for sulfur content in these products by solving the following equations: Refuse ash - Raw coal ash Per cent yield of washed coal = 100 x Refuse ash - Washed coal a^; Per cent refuse =r 100 x Raw coal ash - Washed coal ash Refuse ash - Washed coal ash These formulae are given by various writers^ on coal washing. ^Standardization in Coal Washing Reports, Delama ter M. & M. , March 1912. ^Coal Washing, Wendell, Technograph, April 1915. 99 SCREENING TESTS Screening tests on the ravr coal, washed coal and refuse with chemical analysis of the screened sizes show what size of par- ticles are being cleaned most effectively and what sizes, if any, are not being cleaned. One application of screening tests in loca- ting the source of trouble in an operation v/here satisfactory re- sults are not being secured is shown in the following table, giving results on a coal which v;as washed by jigging at 0“ - I” size. TABLE 8 Screening Tests on Raw and Washed Coal Size Raw coal *fo ash Washed coal *fo ash % Reduction 1« - 12.3 6.8 45 12. 0 6. 4 47 - l/8« 14.6 7.7 47 1/8” - 20 M 18.3 11.0 39 - 20 Mesh 22.0 20.2 8 These figures show poor v/ork on the fine material below l/8 inch in size, and practically no reduction in ash in the sluge ; through a 20 mesh screen. It would probably be advantageous in this case to screen the raw coal into two sizes - 1” and 0 - -i” and ^vash each size separately, or to screen the washed coal and re- wash the material which passes through a ^ inch screen. SINK ANB FLOAT TESTS Sink and float tests on the washer products a.re ordinarily made in order to detemine the amount of float material or coal be- ing discharged v;ith the refuse and the proportion of refuse retained in the washed coal. In as much as the separation of coal from ref- n*: ' (I i V' L ■ ^ i : L • • i ■> ' 9 :: in ' • , . - • j ■J V' O'*"* 'r ;•.....• . - 1 5 .* * a si n Yi :. XaC i :•-. . . «; .♦ '■■' -'■••• oorr.oi)!- j.-.i:,./ -:yi^ «ox ^ 1 , 1 ' ,z •o’f.tnt* j o-r -'V r.i'i * -.-.t v.; » .. " r - .J. 't vnJ _ M r * J I j -* .'u V'-f h'' fJOOL' .‘on DTK »{- '-f' X.KOO .a n: olMij.’.n . .K-). - .IJl'CAV _ i?--) f ,-r ‘ : J “ t : :- i ; ; ■' X»QO ' L»snr) rsi^ * aca > " ■'- • ■ r.t.- ' "■(,; -. ■ .'■'■x J c, •f- '■ ‘-1 ■( rri ri-.^i ;Jt:!!V^':' c' vx. ..-•; .)-i- ' n-xr 0 ». /41 A i -« • • > i Ly' ’ 1 -’ C* -C -:.'0 r'_.; -- tit . -■‘0 . ' •: X i w ■ l' >.. i)/' ■ * ,i vX •■•- , . : '.''xi . 'r C- -«-»• » ' ‘ 1 '^ . . C-'i < ■;/.oar: -zv ‘ >M f ■ ' J- 0 '^o'i ,; •T .>a‘G . ■ '» ••/ G 1 - ^ - . - V W OX"'. gg;jo:.:g iX G.;i r?'^ 1 i '£ ,5, • O': • '.■* ,G ; . Ow aX L ';il / / C;kj C’-Ig 0 .iT.tS ^ \ t I .t ,„i G' '/. n . ^ ) J. ? - •.♦ - w .idiii. 100 use by washing depends entirelj” upon their difference in specific gravity, the sink and float test is the ideal method of checking the work of the washery. Such a test when very carefully made gives a practically complete separation at the specific gravity of the solu- tion used; and comparison of these results v/ith the results secured by washing gives a measure of the effectiveness of the washing oper- ation. Having determined by a specific gravity analysis, as de- scribed and illustrated in the chapter on ‘♦Principles of Coal Wash- ing”, the specific gravity of the solution which makes the ri^t separation to produce the maximum yield of washed coal of the re- quired degree of purity; solution of that specific gravity is then used to determine the proportion of sink left in the washed coal and the amount of float coal left in the refuse. A machine which is now widely used for making these tests was developed by Mr. G, R. Delamater^ while operating the U. S. G. S. fuel testing plant at Denver, Colorado. This machine , caviled the De lama ter Standard Sink and Float Machine, is illustrated in the photograph. Fig. 16, It consists essentially of a rectangular cast iron tank with rounded ends. A strap iron frame, which may be rais- ed or lowered in this tank by means of a rack and pinion device, holds two ten inch brass testing sieves side by side in a horizontal position. A ten inch open cylinder, which will fit inside the test- ing sieves, is supported on a track in the upper part of the tank so that the cylinder can be slid along from one end of the tank to another just clearing the sieves when they are in the lowest posi- tion at the bottom of the tank. %ines and Minerals, August, 1909. 101 i?’ig, l6- The Delamater Standard Sink and kloat Machine 102 To make a sink and float test the tank is filled with a solution of the desired specific gravity and the sieve frame carry- ing the sieves is clamped in an intermediate position so that the cylinder rests in one of them forming a continuous cylindrical ves- sel with a screen bottom. The sample to be tested is placed in this vessel and agitated to thoroughly wet all the particles and disen- gage them from each other. It is then allowed to stand quiet for a time to allow the heavy particles to sink into the sieve and the float particles to collect on top of the solution in the cylinder. The^. sieves are then lowered to the bottom of the tank; the cylinder with the float particles which are in it is carefully moved over to a position above the empty sieve and the sieve frame is raised to the surface, bringing the sink in one sieve and the float in the other. The two products are rinsed thoroughly with water to remove the salt which was used in the solution then dried, weighed and sam- pled. In this study the Delama ter machine was used for making tests on coarse coal of jigging size. In working ivith small coal, such as some washeries are now handling, through a -i-” screen, or through a 1/8” screen with a large proportion of slime, a need has arisen for an apparatus in which all the solution used, as well as the coal sample, is divided into a float portion and a sink portion and each screened or filter- ed with the respective float and sink portions of the coal sample. The machine illustrated in Fig. 17 was designed for this purpose. The apparatus assembled ready for use is shown in Fig. 17. The three separate pieces which make up the apparatus are shown in Fig. 18 and details of construction of the barrel are shown in Fig. 19. The machine was made in the laboratory shop, of a three inch : -n o; o'i lo ari^uXo?: T' ijj"!. !ii r.X ai ;or i:i s**, ^nJ LfTirTic- V ■'■’.• In one p?'o f Oi ’Ol?; . ,...>,■ J.C f nc^O'IDri i iJ’ir i.i , . - .- ,;I ir-L'p*r;' 2 r oJ i^,;; i)fi nsa:; o:* r!oj^ -• bn c;i; o;?f:i ' ;ir -.j L: :^;:*cd .-'■■‘-il- ’ ;to.U^;-. ,)r, -.*j> :»p- qo-* .0 * 5 dXIoo 9 /^ :>.'jr.{.I v-^ . ; .' . .*/ t i«v;. * 4 .. . ' ■ n i ., 0 .; ; ~ :^'\ . n ov: Ic 9.-:. iw' oil ntjlXX^o.; - WT i /■ -DX-n: -i . -tj cooorni *;i - ■ ■ I : i ini «•-' ff»«e 'ii.'ii -sicrt^ V o- -^oifivoi ®ir ®’:r • .Iv -iNr 0 -''i OJ ?'-<■'! ■J’ f. •. ; ' .%■ '1 ’ll >vfi; C'>.;V/ -.'r ?norj .'^U" ‘J i *x”. 0 / ^ ri nri* ‘ '1 - OVQO,* '■ • ■ j>j^* M"iriC 0 . >1 • i ^ f?. ' I*' ~f , ^ jj*5 '■' **3 u'f’*'- X. ■'- /!•■'::). fj !;■ •■ .t ' ^ n L' iJ 0 )1 : .arff >y' LiniUti.:.' on- 01 ; i V ■ 1 0 '\ i ! n ■J-*- - 0 “* - -‘'bOTi^ V V, O3i:-io”- ;.rlcT.:Ior f.;,‘ ni <- 'i. -in. ' I O'i h*'riij ‘ j j .-. .<..1. .1 . ^ .,;i.J n.i , . -.;j • >.^ln ii.^. oli. i'*) Xiicj n;'rr>,i'i .... ‘ ’ . " - ■ ■•’ X J- .« '•? . l:> .t r : - i -.’'x 0^7 « 1 ■ i;. 0 'i;':t • , ■^rio-' ’' • . 'N •' • *■'7 ■ ' ' 'I > ’ -I .. . > ^ ^ * ■ • - - ^ ... .i jc .:Ci M 'X ': OT'J ' M,: , X . 00 ,: •* - •' -r ■, ■ '' 1 -... :.; .ioi f J . i VO i-f:,'”:^ ... not.-i-X'^ X.:i-3 .. , noi.i* . '.niiv: X .;_D ■> V* ; , d'uiO'iOc? :(niB 5fi.n X ;• . r'J -xo'i i,c.-ih> ■' .i. -. ni .11: o-i* .- 0x7 • '^. ■'.*■ » •' *' - V-'- :'•'£ X( '“O'-iii iflo+’.n-ijiQi.Yje ft".'*; , 'X-t.'*: '• ■■ ‘ *^ :': ■ X q:i :.- - yx.nl -o.; ii .c '-: ''l:n a~ lJDin*iuico X ' ■'* ' VI ».■ X f:i j .... C 5 ii%' ©.iX-noo . 1.1 . . wer' .ioi {‘‘o' oX *l ex . *' f: ' •' i ’> Z Z\‘l '.*'■■ ■ '' o .;’• .' : ., oil '. 'll , . i' 1 , v> M 7 m i 103 « 104 u L 1 ^. ¥ V !••' ■.* rA •% J •* k V 105 ricj.H— D^toih of Darm.1 of f/ew ^inK and n oof Machine roundway stopcock valve, a piece of four inch galvanized pipe and tilting frame. It is so simple in construction and operation that very little description is necessary. The bore of the valve plug was cut out to four inch size at one end a.nd almost through to the other side of the plug. This small end of the bore v/as then filled with babbit so that the valve plug instead of a three inch round hole through it has a four inch cylindrical well in it as shown in Fig. 19, In the valve body one opening was cut out to four inches in diameter and a galvanized pipe ten inches long and four inches in inside diameter was soldered on. The opposite opening was closed with babbit. The four inch galva- nized pipe and the four inch well in the valve plug form the con- tainer for the sink and float bath. For convenience in manipulaition this barrel was pivoted on a tilting frame fitted with a catch at the bottom for holding the barrel rigid i«hen in the vertical posi- tion and a stop for the valve handle to facilitate lining up the well in the valve plug with the bore of the galvanized pipe. In making a sink and float test the valve handle is turned over against the stop forming a continuous cylinder of the pipe and valve which is filled to within about two inches of the top with a solution of the desired specific gravity. The coal sample is then immersed in the solution and stirred till thoroughly wetted. It is then allowed to stand undisturbed for a short time to permit the heavy particles to sink to the bottom and the light particles to rise to the top. The valve handle is then turned through 180 de- grees, care being used to avoid jerking or jarring the machine. This separates the heavy particles in the well of the valve plug from the light particles floating in the upper part of the galva- ■=; ' K 6 .’'i 't:'o> ' :->ofti- , ■* Xoo’. *.’; ■f^^ iioiv c'l'qo ; : , - f. ‘ '^.cr nx . oT^rcjia oft .* ; , ml * aoG* r- , -pf'Ofjr :: :''• /♦ ^l^*t X 1 £»V ;i 't './*■ c.' - ;f'.' .‘i ■ ■■ ' -rC.'.y of''* -''X'-io ■'ro((^o t .b i.oirlj -ucoiilA iin,: i»ns b" : ■ ■'j r-i SIJJ3:S dstv b3'SS.: t •.--* orj . ba^ /I ; c •• ■ V- i .1; /iC’iff- ■’’.Off iMijjort .Iv.ii o©'‘»:.i.? .«5 '. j b.t. oJtai '7 ^ ^a-.. i(] ♦ ' r :•- ".r-.'-'t * :. r.I Xlct; , •/r*;'': ;. •.'•.'ii'’ ; j O ^TftX oi ' Jl/O 1 f . a ■;! i. • j VC! ■; xvj <* ,;.3l ;■ '- ai ' a^-fanl "WOl ‘^s: c, .-.: »r»I<©/il LUOl a . - (■ ■"}. Jb-- I-< c V ‘ •« i ^ ' vlor' .va Ju'; OTiJ , ";nai : ©qx q o . 4i' ■■ vt c.r\ Liw 'xol iii * ^ ■ 1 < . - >•> rj;fJ a*' J ar fl.i 'alJ-.Xa V i..; Hi *tv-- ? ..«, 7 .;Cr^ -v !.o.''.:j riJi - --'j.*/ •>..:***£'- . ifi. rj . Ji bf>J.'vlcr KMif ex.' j..a.'J':.' a'.' ..i .'5ic:.' i‘- Xoi';; ■' or' ' . I >1 ;in TO't ■* . : :.,v 7;.,* :-.j i 1 "si lin/ifi B’r ■ y ’;d .{O:! -k rl9 noi-: ^ , ■ 'b-'-.; " o-'J c ,qoo' u*«^ .' v, JL • '/-'Iq a* / ;. J ;:i .La - r:7;:.. J‘ O’ vJ 2-') >.rj Offj Jac . J i v oj rl c i.'.' > y r ’ li .w siv 4 ©X'i 1 ' ‘ty.tct T ! ^ !'■'■ r I o'‘.f^n*. > laon oitAV J-yj ii.OTi»i . ‘ '.I? 1 ,’.:.x.v • .- » w 1 1 i «: 0 . ■ .t 0 1 * V/ r. o€ f> r 03X a- : j h«in * V* c • v/ .■ ■ i X .' i. '•■■:) ' >. . V.:.’ ' X'icv^'- *:o': b I'XJS^n.'? ■■> : .^ ; XI f):!J c . •: v>. X ui.^- *?(rtXr! oJ ,,:<0 ■i: ■ ‘ b ‘. vit: L' * rio ■ Li ovii .’.v L>vtT ^ pii^' ■ iq jjaiil'io;, Mov... 03 bm.u .'>i- i rl iv ^ *’ : ,ic :f ic IC9<* It : a* r»9X:jid?*i j’i \Vi- Qi. , ,vj : ii.;;oX ■ 'J. oi ., 'r^^a irlhiX 107 nized cylinder. By tilting the "barrel of the machine the float coal and solution is then poured out into a fine screen or a filter, the so- lution is drained off for use in another determination and the ad- hering particles of float coal in the machine are flushed out on the filter with a small stream of water. The valve is then turned back to the open position and the sink coal and solution is poured onto another screen or filter in the seme manner. The products are then washed v/ith water on the screens or filters to remove all trace of the solution used. By using this apparatus v/ith filters for washing the products all the sample is recovered and there is no loss of fines by suspension in the solution. The small volume of solution used makes the operation with a vacu\Jim filter fairly short. On samples from which the slime has been removed a ICO mesh screen is used instead of the filter. This machine was designed to make the separation just above the top of the sink in tlie cylinder so that practically all of the solution carrying particles in suspen- sion goes v/ith the float. The float, therefore, includes particles of the same density as the solution and lighter. In the literature on the subject of coal washing the statement is often found that the sink and float test gives a 100 per cent perfect separation. This means on the basis of the specif- ic gravities of the particles in the sample as they are at the in- stand when the separation is made betv/een sink and float in the so- lution, A number of tests in which the float coal from five pound samples was retested immediately after the first separation showed from one to three sink particles in the float. The coal tested was an Illinois coal at size in which the average proportion of \-* 0 ^ u . "...u .r rx ft:!j onirn. I or' :*: i.vo brr.llS^ ’ loitai firiS r\n’i.‘LiJ , . to n?c: '•* " s.'X ■ g^i 4; oi. J’ j'Xo'- '■' ■- ■ ■ t £j:i:l’ : r’i 8 »jj .'lo'l ’I'ia •i'Jt:’' ui l.’ ' I : r-o ' 'r*Ka-/ o.ii/'j.V'f r:i laoo ^ -ol’i -jiJtaci ; .' v; '?r.C-'V £1 . t-ov’ lo ' fl ■ .i.-. X .703 r>o’* o;t .- ' X aocf aeqo or* ex? ■!;, D.'* ■( .! .1 1 . ■' /too ioc t'‘ ^*orr^ rrj ■; j -,c*I.i;'t *i / riir^.tf .j :• -J” r.o ner.X J I ;iv' rrjrx 'O.;.! ■( . i,)t/ . - 'cic.is 1.03 ‘' .' 'I ■ ; .-o.)*-: ;» 1 . ' ‘ ". > ' .'"’j r U ’ '■• ^"'l * ’ ' t'i * ifl :'.Ox rrt » rs'.', 0 "I r : n r: r T ^1* t •:*:vo "/ . ■ n*. W.J i'*r '*0 *»iIJ atfF'U- noi''. .'. '> ^ 4 * \ •-; S:iO" C '.: i I'q-vu:*)':- r' - , ,3-:' ' .I'-! -V5;t ;:v^’iv 1 ir. a/.' noi' or.;- r,j . 0:3 too ■ ■' • j •> -» r-.j* , i 3 -!. ■* C* jt ■“ v' lO o o * • ;- pj. 1 } . . ■/ * ucri, ' , - ..: r.i 30 : 3 l"--r>i 1 . ''CiJ ; 00 ^- 00 r 'IC Vt j >. ; .r'^ ,. 0 X“ or. 0 'J :iox 3 - *g 7 »' ' '■,-' *’0 .'.\tJfIon "..' / 0. •.ejjf orce j.v* 'I o } .').,vfO r r Oj: w" •tTftC .7 0 5 o 5‘0 t' .■"; :jV j - ■ X -c a .!■ .Jc' *>-• * riv ot ^ .X j. J :r*. ' X:o, *;OXt O': :i:;j 'it 'I ' - . •■? ^ - ‘ - - -tq: -t ao::': otX .!•■ o o (j ito crooi ’.4 »V c.i oX ■ 0 ..i r.-iXoitr-. 'o (!, . ■: i!” '•'■u”* D.‘i •'(.'•‘■'i;; C.‘ tO ’ * ;' '.rl:: r.i rroi'- }f;.\ .?..;.:0v; '.’ViX ut 1 X 00 -X ol'l rfo.: •• ,:i ’'.’rf'' i I ' 0 - lx X.O'ri ’ ctX '^COw‘ I ■> :>.■: to V o'jX ' :.X X o.':j ■> , . . 'X ‘ o. ::i C: 9 XDlX'ii» .'. XnJ - oo'i 'J c 7 5 .'!f Xto-ro* rol.r: rl 0313 " ’ - “ ^ i - X-cr rlorilil loe I sink was 12, per cent* In retesting the float it was reiimnersed in the same solution immediately after the first separation and allowed to remain only ten seconds in order to avoid as far as possible in- crease in specific gravities of the material by absorption of water* These tests show that the separation between heavy and li^t par- ticles as they exist at the moment the separation is made is prac- tically 100 per cent complete if the test is made carefully. There are, however, a number of conditions v/hich affect to a considerable degree the results secured by sink and float tests. The most important of these conditions are probably the moisture content of the sample when tested, the length of time of immersion of the sample in the solution and the thickness of the layer of raw coal formed by the sample when placed in the vessel in which the test is made. Several extensive studies have been made on the subject of specific gravity of coal. At the U. S. Geological Survey fuel testing plant^, which was operated in St. Louis in 1904, specific gravity determinations v;ere made on ei^i^ty-two samples of central f! district coals. The average value obtained for clean coal was 1.29 p li and for average raw coal 1.34. Nebel^ made an extensive investigation of Illinois coals determining the specific gravity of samples under different condi- tions as regards moisture content. Ordinarily two figures are given for the specific gravity of a coal, one designated the ^apparent" specific gravity and the ^U. S. Geol, Survey Bull, 323. Sta. Bull. 89. 'Specific Gravity Studies of Illinois Coals, Eng. Exp. 109 other the “true” specific gravity. The apparent specific gravity is the specific gravity of the coal including the moisture or air ei I contained in its pores. The true or "real” specific gravity is the 1 specific gravity of the actual coal substance corrected for air and | moisture content. In determining this value the weight of the mois- ture per c e nt is deducted from the weight of the coal and all air is removed from the pores of the coal by boiling before it is weigh- ed in v/ater. In coal v/ashing it is the "apparent" specific gravities of the individual particles as units including impurities, pore , space and whatever is in the pores at the time the coal is fed to the washer which is effective in bringing about a separation. For this reason, from the practical point of view, the "true" specific gravity does not enter into the problem of coal washing, Nebel made specific gravity determinations on freshly mined coal containing the natural vein moisture and on samples of air-dry coal after immersion in water for varying periods of time. His work led to the conclusion tlnat the coal in place in the bed is saturated with water, and that air- dry coal immersed in water in- I creases rapidly in apparent specific gravity during the first hour, j I This shows that in making a sink and float test the effective spe- \ cific gravity of the material will increase gradually from the in- | stand the sample is immersed in the solution and particles will be | |l continually leaving the float and joining the sink. Nebel’ s tests | showed increases of from 0,02 to 0,03 in specific gravity during thej first five minutes of immersion in water. I ■ • ■ -r ;) J "Hi ’Z.' '• r-* X -. : . ' ] '»I,fx A ^ ; ^.n .. -■ ' or. : 0 •> -> 'Ci, 0 X or’ • * V ^ . ' M s. S '..Oit vu • •►- uc I. '■' X^i:J n 1 ^ . u: ' V *\’ O ft ■• ' /■A s ,. *• •'t > .* J! Ti, MiTn 40:1 •Iff;; - 1 • .-A — V. ■* - 1' ■ . , • r \ . X ' • * ^ ."1 < 1 ■• ft in ». A oy::6X' - ft * t - ■ 1 ♦ t . ^ **-^ .* iuXo»rt mTi.i.: #; ^'■ • ■ :v Ic'iii i}. ' ♦ Ta ' ' T . X t<. ; f-.-'J 'K .~oL^ •/JJ ; ^ •ii ' ni *:■ Si^C.- V»^. •.' X ■'■ .'i ilOXC’’ ’ t.*'. A? £iJ r.,.'00 '■*' - M li »‘ — ^ ,' ■ «» ~i_T J rr I ••■: :■ i. i . O M. ' * 0 J" ft.'. 3h (■ J.'llccr J, ’O: - X 4 .,*;'^ » ' -. .Li .. OD ij ^.1 ■ . I. •. : ' ' X 'i : a'lcl* ,y vj o*'t* . - •■ ■ -^Xtlicr '•- iX ;7: 3v: •':*■•: C, : rrj; <,; v r_v;:>..iT -v , .!. .^D « . 'I .0 ";.i :* -/-■ -• ^ ■-■ i SD'il./ .:i I«£ •ri l ic-j . • J iS \> S. '. ' .j. •j- '■- • " - -I? T r. ;-. r I i ■ ' j; J ; 7 ns,' .. A...' n^i.u r ft." .'.oisTt/Xo^ - i-.L ir? ■ 9fU ', L, .. a.c ' .'i i''. XtinrrQ n*- -♦ ofi . £/ 4 ' n . .A* V' fi- ^ ' fij r? f. I '1 :ir'viAjoq~ ri' . I » * ^ . f ‘ 4 - - 1^ li T ii , A ^ .51 ^ ri.'* i tx 9tU i- ane wLjm« 3i>»3 m liiij li at: , . V' a: A 110 More recently T. J. Drakeley^ determined the effect of drying under various conditions on the specific gravity of lumps of coal. Samples of wet freshly mined coal continued to lose weight for 586 hours when exposed to the air. After this time the specific gravity varied with the hygrometric state of the atmosphere. The maximum variation in the air-dry sample being from 1,2008 in a steam heated laboratory to 1.2261 during a period of wet weather when heating of the laboratory was suspended. Tlie size and shape of the vessel in "yihich the sink and float test is made will also affect in a measure the results attain- ed, It is apparent that two duplicate samples of the same size, one of which is tested in a tall narrow vessel, and the other in a wide shallow vessel, will not give identical results. More time will be required for the separation to be completed in the tall vessel and on the other hand, more difficulty will be experienced in removing separately the sink and the float products from the shallow vessel. The important point in this connection is to make the maximum size j i of sample treated small enough in proportion to the size of the veo-| sel. The thicker the layer of raw coal in the solution when tested | I the more chances will there be for li^t particles of sink to be I enclosed in and carried up by the mass of float particles and vice versa. These investigations show the necessity of standardizing the conditions as regards moisture content of sample, time of im- mersion and apparatus used in making sink and float tests. ^Coal Washing, Further Scientific Studies, Colliery Guardian, March 12, 1920, •T' 3 r' »• J,;- ;c*v -^T^©i «)'i ■'i.T-, o'Wo- i rr'J" lie /^r:v^Jl^^.. !»L'oJt"t^.'.,«^'- 11 ) ’ • « r- : .' - , •^'tUr v) r^oepea C; '"j J • r.o'iv.VTf jTTi ^«*r • -iJtr ct't r rr l^d r:c* -• O' ' -::i ,. •>’V rA»t .,>'-* •j. oC'.: Tic-rs*:v:' : -j* ♦ io r^rXJ- ^ K*' ' ' ‘ !i ty.i ^1 • /' w f -^,^ 11 ^ i , :>,• ~T Sf'<' ’ :. . ' '-C 1 1 )'.* o;. -!.?):’ 4 ;u ^f.i! \r, ' - . ^ ■■ '■ ~-* . L — j :' :i •.wOt'* 'oiijE© ■ ••'’’’ --'■ - ;.»Di: ;• r; > V ■> ‘ - f ■?• -.A^j o>.; >i -•■. f-^t' .',. utiiyy’Z.y - -• WOi.I i,': ;- i : ; ■C'iiii r ri. . >., • ; y, ... r^". , ., • . r*. ^ • » * - » • J U> * V 0 --•^v ':: c:;.; «o^, ^ ,, ., ... ■^, al ff *n.‘ y<^' 4 ,*..' ■ * 'J' ^ - ' '>3 IT : i . , .i;o-x ,•; .X I ...(r, , r o r ’i J X . aJ - l-.o ; j... -iC'i w •_ ,o .vs?y.:!X oiii 'ii! ir ir*, n’ " ■K . • »{f - . i V 'J J-.W - .'; »/i;., a . ot •.'•r-);;. T.rj,. ' ■T»fn*!.i5iVo j Iv f,:v. - ^ ; ,.jX 1 :?jj 4 j.: o.'' -.-Xfco &xi -3 i X. •'£ t> •ti r. V" -Xi I -;r;,vjf>»i y.f? v;;n’« n vj .; ,->v ■*< " ;3 - -.-T,.. CT..«SiO.„ C. ‘ O j ; * >T .io*5 ■ , , J •-toJ 3M0l'y ;:.: :..,i • ; ,.x . n> .• . f I : j. i : ^ ' i i I M f?;* >. ■-, .•'..' ,.»J ’U ' tUi • . .' ^ I »«%>* Ill These are conditions which can only he fixed arbitrarily as there is no one naturally correct method of procedure. For these reasons the sink and float test is a method of analysis which must he carried out very carefully in order to he of any real value, moreover it is a method which is easily misused to misrepresent the facts about the operation of a machine, as it is possible to secure most any result desired. Therefore it is just as essential to know the conditions under which a sink and float test was carried out as to knov; the results. At pra.ctica,lly all commercial washeries the raw coal after crushing goes throu^ raw coal storage bins which hold several hours or perhaps several days output of the plant. The coal when it is fed to the washer, therefore, is usually in a more or less air- dry condition. Largely for this reason the air-dry condition v/as adopted as standard for ssmplos for the sink and float tests in this study. The time of immersion was fixed at sixty seconds after and not inclusive of the time used for stirring the sample in the solu- tion to thoroughly wet it. This is sufficient time to allow the | sink and float particles to come to their respective positions and | yet sufficiently short to minimize the effect of absorption of solu-l 5 } tion by the coal particles. In tests carried out in large glass | i cylinders the solution intervening between the float product and |i 1 the sink product appeared to have come to approximately a state of | fi equilibrium after sixty seconds, althou^ there is always some move-l ment of particles of intermediate density in this part of the solu- | tion. I In the Delamater apparatus which was used for tests on samples of coal coarser than one-fourth inch in size, the maximum ft*: i , V. I t r* • . V ni ■-..or •> Tr. ^ o:;; i>.i ..r-.r:r z^- : -v., /i - *'• '' ■ - . Cu 'J arfv* V..J ii.;,j:il' j’;.-- +., 0 ;': yfi? i't'iOv*i:.' ■','. i . ; i; ' • " iO w .. : • ; . ;.t . ’’i. :o ’4 *■ M oJ ,-.V •^: . 1 ri'. . 1*'- - . C X. * J ' ot n ':?^u4 k'v ' .^xio tvj’v? r'f'iie'i.Ci r i lb • .’Zx , . i * ^ ;> ’ O.J 1 kiiti k ■'i % ill 112 li ! size of sample treated was 2500 grams. In the cylindrical machine used for fine coal up to S/S" maximum size, the largest samples | 1 treated were 400 grams. In each case this gives a maximum thickness 1 of . coal in the vessel of three inches. The important thing in making a series of sink and float tests in the examination of a washery is to fix upon a definite standard set of conditions and maintain them consistently throu^out in order that the results may be comparable. SAMPLING FOR SINK AND FLOAT WORI^ The sampling of coal for a sink and float test is more difficult than sampling for chemical analysis, because the coal as tested must be at the size at which it is washed and cannot be crushed before quartering as in sampling for analysis. Larger sam- ples must therefore be taken and they must be handled as little as is consistent with accuracy in order to avoid breakage, which by disengaging refuse from coal affects the results of the test. Blythe and O’Shea^ in an investigation of coal washing in the British fields made sink and float tests on a number of dupli- cate samples in order to determine hov/ large a sample must be taken to give accurate results. They also made tests with colored coun- ters mixed together in various proportions and came to the oonclu-- sion that a minimum of two thousand particles is necessary in order to keep the mean probable error within 0. 5 per cent. On this basis the minimum weight for various sizes of coal is about as follows: ^The Examination of Coal in Relation to Washing, Trans. Inst. Min, Eng., LVII, p. 261. " rriTCUitf t :r :.^. b iiu'ir.* 1 r.i W .Cyj- ■:. *1 -'’ ; • C lx' ■■ ; I' ■? c. .•/.' ■C. oy ■ I - o1 . f - tt t' ♦ m CO*- s’xr'" •••x^ •vf |. - • ■ * ' ■- < j- J.'l : .' od^ Ili i*CO , , ,U-. ...,w. ..Via to Jivl-. .3 « iiJ S;:itf; : :,.j.*,. ,, ■T -" . I 0 ro-..v T.f', oi ai v.ortL.p ■ , 'io ..ci, ;.,t,'is.: ■ o..: cj -' 71 ' J" ■ ‘ ' r! c ' •VwJ ;—r. t.toi^ ion&> -r>: b-r;D •, -:oo D-:; ASVt.. *i^tc »:] ^IFIOTt I . 0 .;”^. ,. iti..i'I /' -.iw 3 .-. f ., ■-- ->' ;■ -ii.'^:« t 4 .i*oi> .’j;;,, ;., ’ -j,!)! r!::r*^ *Xi.»r ’ •> J| 1 :' .'..t.'iJ-'Cj- ;: ...^ _ , v .: ' . '*>fi J - .... aw» 2 .*, -jj J' j-^ «cfj-^^,f;'i:r - ■ " ’) «:\.Ih;.’t. 'io'.i ri e-^ ;,r:/-H.-: .v - ‘"I * '■ - - - A.U .. W . i, L . .. ■♦^ - •' 'r.- '■“* ■-•■■•-- Orf f>-: .’ioiii • • SKUCt^s^iSq ■“' ' ■ f.i:c'V 0^ - OW.IU vo>.ti;: y • .c^'^ i^r i , . ^ : r.oy. eiT n I.OD -ri . u-'t.;. - J, , .j. ' - XaJo Tc rroi^<--.:;i^cevfU ctu'r.Jt X-;$' iln- nr/^vM . ^ ^ io *.f. j. .jf v„ w-Cii- jfrtiv .•.'. .;»5 x7. dnitliZ •vli* 3 ^r a> r^C^noj.. o»:i 3 fV -::i;cy ■ oioloo ,L: 1 .- c^.:c^ sh. ocU vs*j:' , i £ u y 3.1 y* > --i-j;.-. Ov. 1 ..;^ Ow e..T’ ':.> 'j:c? ^ oi- ;3£.'x..v' nl loxi^o-u.* fe^iri;: r ;r...t ' * :x£ -0 r?x &1 zo£ijJ:‘i:y ; Ixteetforf.^ owj 1 ':' 'awai.t-i'/a .« .-t.rfj- acxn .iS ..0 •X;^., .. 10 M 3 sl^.fvid'oiji ;: 4 ©;;- g.'j' qeek i>. ,.^Ql f;,: ::i ixioo ■ i ; i;j;:lc' 3 UCi*x.:v 'lqI ;trf£io :7 ;^fci^^:£T ^.i.r ,',. irrc 'iiv o? :'i £ oO 1 c • , X V S , t ^ Jt , ' f 113 Size Inches Weight ^Tirams - 1/10 10 1/16 - l/e 50 1/8 - 1/4 200 1/4 - i 1000 Over i 20,000 Tliese investigators apparently did not give due coneidera- tions to the difference in the nature of various coals as it would appear that the accuracy of sampling would depend more upon the net amount of the smallest constituent, that is, on the wei^t of sink in the sample, assuming that the sink is the smaller product, than upon the gross wei^t of the total sample taken. For example, if the total amount of raw coal to he sampled, contains only one parti- cle of sink, no sample less than the entire lot would he perfectly representative; on the other hand, if the raw coal were approximate- ly half sink and half float and v/ere perfectly mixed, a sample con- sisting of only a few pieces would he representative. From theo- retical considerations it appears that the minimum -size of sample which can he used depends upon the necessity for compensating errors due to imperfect mixing of the sample and on the proportion of the | smallest constituent being determined, j On all the coals used in this study, preliminary sink and || float tests were made on duplicate samples, taken in the usual man- j Ij ner, in order to detemine the variation from the average in deter- j minations on samples of the size used. In addition to this precau- \ tion, in 1919 a general investigation of this subject was made using a coal from the Sharon Mine in the Danville district in Illinois and I one from Ramage, West Virginia, The Sharon coal was a hi^ ash screening containing a comparatively large percentage of free dirt, such as is used at the University of Illinois power plant and the i u C'.f » ;n nV - >• J . . jw r. ^ \ •» wv« OOu oct.r ^ V - ■ "V ~ V -ot)innoo ^lr^ ^ ton I:^ 3 vni seaxiT- ^/4IOf/ .?/ •, 'ii '- uii wXXOi'lJtT ■ Ci im/ifii** 9;\^ j '■‘t'Tt ii ^ ■ - .:aa, OTtoi" X L’-’ ^iiJi'X^rieo \o \;o or.J ■ w . “ w * I « ■w- c ■ ■ t ■ OlfJ j Lv orroo * 0 0 X ■.>- iC vatfOTT 1 • t ^ h 1 w * oii/ r • .*1 1 - J V \ :j/aa3 of{;V. r U - 1 r •,r.o " or ■’ * - _ Tit, 2 I.r \*c* 9r‘ • ■t -'tn } rrf ■ -. . *^r-> orii rrjqi ■ ■■ ‘i O': :o \Xao • . • .% ■ . w • - r~ •i V C.'.:i)0 r .'•!X re ;»:• AUXt; i. lii^Jor' f2i. a^" 0 r • L. I'O-.- •» w.'. * ■ ' -i" o/*;*!::ot3 C M ‘ e .ic 'Vo “ r- - '* 0 • * r • o \ : • r 00 ■a'Jd'i ‘j .'^ e . 'cort'' p c •’5' n ; X- ^ l5‘'..9'X > -4' V' ' - r n s , '- j .« ■ ■ »j ‘'i 'X::oc qji :* ' ■Tr^oXv Ato: ;io "■•VO leciv'.': --I . r e;uv|'^:oy uo> iv'r*^ t^njn -..-f:: no-qi; avr'rrq./T bo«tr sj" .tev rfx/i:r{-’',f' _ -v .!Oi^'i-.jo^:tr erfj no -jo av‘v:i- *c 0>xe(^r: s*ijh, ^ - ' ' iS * f’ -nians^ i 5 l/ 3 niif';' J i< >f‘j *’d“»nco ■* yffs?. IX f! lYj xi .Z.>VB>:_prU •:,;. rts>; * , :^p. c ■.,: ■■,Kk..;.. .-..> «xow q^^9^ l , iob (T/ o-j!i-.v. o.,.. aoi-. T arti 9.ti«neJ-afl o* »e;)To.: ' •>a'i.T 3 X -.f .^x noX^i >h-. ’I oh.,*- 'io fjQXi7i::^3 ri'’ - - ‘ - 3i/ obhc: .*j -V ni.-:;* 'x-. noi«‘..'-.X .:. .'x::nr>y- c^oni-. ,! /:: -oi'i^n.V' o^Iir;t^ s»fij ni o-iL' no^. m ©/{; .^oi'> ‘LQr fr* , * * ¥ «!■ ff-t.’. •.. c-^ IfioD nrtio<^ '■*’ ■ ■' ^ “‘""OiP-."! oj/i9i \;,tav^#o;.e'!riori ,‘j ,;oa jr > n.,o':'.) a\j' ) ;. Several methods have been pro- posed by different writers for estimating the efficiency of a coal washing operation. All the formulae which have been published are based on the sink and float test or a combination of the sink and float test with chemical analysis. Since the separation made in coal washing depends entirely upon the specific gravity of the par- ticles, it is logical to take as the standard of comparison the re- sults of a complete specific gravity separation made at the ri^t specific gravity to give the products desired. If the specifica- tions for the washed coal require that the separation be made at a specific gravity of 1.40 then the effectiveness of the washing op- eration is measured by the extent to which it approaches perfect separation at this point, discharging as refuse all particles higher than 1.40 in specific gravity and as washed coal all particles v/hichf are lifter than 1.40 in specific gravity. j i LINCOLN’S FORMULA I F. C. Lincoln^ calculated the efficiency of coal washeriesj 3 I by the following formula: Efficiency = ^ float in washed coal -(- ^ sink in refuse This formula, as explained by its author, is useful for purposes of P. 57. ^oal Washing in Illinois, 111, Eng. Exp. Sta, Bull. 69, 118 comparison. That it does not, however, accurately express the me- chanical efficiency of the operation is shown hy calculation of the efficiency in a case #iere no separation of refuse from coal is made and the efficiency is therefore known to he zero. In this case the products designated as washed coal and as refuse would each contain the same proportions of float and of sink as the original raw coal, say for example 85 per cent float and 15 per cent sink. The effi- ciency as calculated would he _ 80. 4-, ,15 «. 50 per cent 2 “ DELAMATSR’S EORIvIULAE In 1914 G. H. Delamater^ proposed a set of four formulae for calculating coal v/ashing efficiencies under four different sets of conditions. Having determined, hy subjecting samples of the raw coal to sink and float tests on solutions of various specific grav- ities, the solution which makes the most desirable separation; the | float on this solution, called the ’’permissible hath”, is designatedj \ as standard washed coal and the amount of this float product as a | percentage of the raw coal sample is taken as the standard yield of i i washed cod. The efficiency of a washing operation is then calcu- \ I lated as follows; | , , I Condition (Ij where the yield of washed coal is standard and the ash content of the v/ashed coal is above the standard. i Pav; coal ash - Washed coal ash Efficiency — — Haw coal ash - Standard washed coal ash Condition (2) where both the jj’ield of v^ashed coal ^Coal Washing Efficiency Calculations, Coal Age, May 2,1914. 119 and its ash content are above the standard.^ Condition (3) where the yield of washed coal is below the standard and its ash content is standard.^ Condition ( 4 ) where both the yield of washed coal and its ash content are below the standard.^ Apparently these formulae are based on rdec4« 0 ^^ t^nro e>^* ficiency factors, a yield efficiency expressing the relation of actual yield to the hypothetical yield corresponding to perfect separation and an ash removal efficiency representing the ratio of actual ash reduction to that secured by perfect separation. The numerical average of these two efficiencies is desig- nated es the general efficiency except in condition (l) which in order to make it consistent with the other three formulae should be changed to Paw coal ash - Washed coal ash Efficiency — 100 . - . . Rav/ coal ash - Standard washed coal ash 2 While these formulate are valuable for the comparison of two or more operations all of which come under the same one of the above four conditions; efficiency values calculated by the different formulae are not directly comps-rable with each other, because the physical significance of the relations expressed between the differ- ent factors differs in the various formulae. In condition ( 2 ) the yield efficiency is expressed by the following relation betv/een ^The formulas are shown on the following page. jyy- •> - X*: .M - ^ -V ' ~’^Bf r " t aP" S- •« ^ ■ -p ™ ■■ f, ■■'I ^ 'C" » ■ ' '< •'te “i Q. ^ { fcv ./•% . - » f \\ ^ \ r^'-- - •m 3 n VI -nr-' » 0 r» * ^ II ■ m' • ■W' O y* - *►: - n ‘ r ^ • Vr W^j' ' ■•* - o u ■ *' ' r ‘ ' rf*’^ .&. ' • *:-v^ • u • - ' *.'-r ■■ • ■* ' ,#*»'' iK , H> • • '* ■ • ?l '**»i « t ^ . ^. - ■ 1 » i - ^ ^v- fVP i. * 0 'll ■:S U-JS’i ■«< ■wN*.'^ 121 actual yield and the standard yield. Washed coal yield - Standard v/ashed coal yield 100 - Standard washed coal yield While the corresponding part of fomula (4) is expressed as the direct ratio of actual yield to standard yield. Washed coal yield Standard washed coal yield That these two expressions have an altogether different significance and v:ill, therefore, give values which ene not comparahle is ob- vious. DRAKELY»S fiETHOD T. J. Drakely^ has recently suggested a method of calcu- lating the efficiency of washing, which is based entirely on sink and float results. Like Delamater* s equations it consists of two factors which in this case are designated qualitative efficiency and quantitative efficiency. V/ashed coal float - Raw coal float Q,ualitative efficiency -g 100 - Raw coal float ^Coal Washing, A Scientific Study, Trans. Inst. Min. Eng., Vol. 54. r . , J 122 Q,uantit£iti ve efficiency ~ Raw coal float - (Refuse float x percentage of refuse) Raw coal float The general efficiency is the product of the qualitative and the quantitative efficiencies* The author explains the appli- cation of his formulae as follows; TABLE 11 Average Working of Jig Washers Raw coal Per cent Washed coal Per cent Refuse Per cent Float 70,25 89.41 2. 89 Sink 29.7 5 10. 59 97. 11 Output — “ 78.8 21.20 ‘♦From Table 11, which gives the average values for the working of jig washers, .it is observed that the concentration of the float particles in the coal is raised from 70.25 to 89.41 per cent. Hence the quality of the coal is enriched by 19.16 per cent out of a possible 29.75 per cent. The qualitative efficiency (19.16 4 - 29.75) X 100 = 64. 4 per cent. ' Q-Uantitative Efficiency . Of the total rav/ material, 21.2 per cent is lost as refuse, and of this 2.89 per cent is coal. Hence coal amounting to (2.89 x 21.2) ^ 100 "0,61 per cent cf the f, total output is lost. coal, Therefore, the amount recovered is (70,25 - 0.6l), or 69.64 per cent out of a passible 70.25. The quantitative efficiency (69,64 4- 70,25) x 100 — 99,13 per cent, I favour the calculation being made as suggested for the I ■'D ■ ' 'v; '-T ' j «i “ if : •*■ B ? ' ■y^ :r 123 following reason: During the process of v/ashing, a certain ajnount of slime is invariably produced. This slime is usually, at the present time, a waste product; but future investigation may demon- strate that it is utilisablc. In such circumstances, the only loss in the washing process will then be the coal in the refuse. The slime question is not settled one way or the other, and until it is it would appear to be more satisfactory not to regard the slime as being a total loss. If no slime were produced in the v/ashing, the tv;o calculations vrauld become identical, ' General Efficiency of the Washing Process . It has been shown above that the process recovers 99.13 per cent of the real coal as washed coal, with the quality improved by 64.40 per cent. Hence the general efficiency (99,13 x 64. 40) I. 100 — 63.84 per cent.” This method has the great advantage that it consists of one general formula which is applicable to all cases and may there- fore be used for the comparison of washers operating under widely different conditions although the practical utility of such a com- parison is a matter of conjecture. The only v/eak point in this formula is that it makes no distinction between the heaviest sink particles of pure refuse and the li^t particles of bone which barely exceed 1,35 in specific gravity. In actual v;ashing practice the heaviest refuse particles are practically all removed early in the operation and such sink material as remains in the v/ashed coal v/ill consist mainly of par- ticles of intermediate density which have been described in Chapter III as natural middling, Eor this reason the figure for qualitative efficiency calculated by the above formula may be misleading espe- ■i f i cJt p. ; , J * 7 f 3 ■ X C.0 .1 \ *) • : . • .f • b ♦ • 1. - - - •, c u . } »'» - . ir - nr' c :■:* •'.• •:> : ■ A •A f . y K, r> f:.' ^ ■ ; • • ■f*T ^ ‘ i .l^^ y r\ ^ ;m ' '*. ' '•) y ‘ A ^ r . • 124 cially in considering a coal containing a large proportion of raa- terial of intermediate density say 1.35 to 1.40. A large part of this will go into the washed coal and the effect on the efficiency value as calculated will be out of s.ll proportion to its effect in increasing the ash content of the washed coal. Of two washers each producing washed coal containing 10 per cent sink in solution of 1,35 specific gravity, in one of which this sink is most all heavier than 1,80 and contains 60 per cent ash and in the other lighter than 1.40 with 20 per cent ash. The first is certainly operating less efficiently than the second. Any of these fomulae are of value for the comparison of results secured with the same or very similar coals on different machines or by different processes, where the conditions of mining, crushing, storing, etc., are the same or they may be of value for comparing results secured with different coals on the same machine to determine the relative washability of the different coals; but for universal application in different operations, where so many variables enter in, the value of such calculations for purposes of comparison are doubtful. The variety of formulae advanced and the variety of re- sulting figures secured indicates the great difficulty of arriving at a single figure which accurately expresses the true efficiency of a coal wa-shing operation. 24, Methods Used In the Study . This work has consisted largely of a study of the results securable by washing coals with jigs and v/ith concentrating tables. Investigations were conducted in the field at operating washeries and experimental plants and more in.tensive studies of the operation of individual machines were A L 125 made in the laboratory of the Department of Mining Engineering of the University of Illinois. The use of efficiency calculations has been limited to the comparison of washing tests with different machines on samples of the same coal or tests with the same coal under different condi- tions as regards sizing, or for comparing the results with different coals on the same type of machine. . For use in the field for esti- iljating the effectiveness of operating washers a method v/as devised which combines some features of the Delamater formulae with some features of the Drakely formula. Having ascertained the maximum allowable ash in the washed coal or the limiting sulphur content, if sulphur is the limiting and the yield of float coal , feature, this is designated as standard washed coal/^of the desired degree of purity, determined by a specific gravity analysis of the raw coal is taken as the standard yield of washed coal. The ef- fectiveness of the operation is then expressed by the follov/ing: Actual yield Yield efficiency or quantitative efficiency =: Standard yield Actual ash reduction Q,ualitative efficiency — — Standard ash reduction Haw coal ash - Washed coal ash Raw cop.l ash - Standard v/ashed coal ash These two factors are combined as a product in order to reduce the efficiency to a single figure. The qualitative efficiency is based on ash reduction rather than reduction in per cent sink as in the Drakely fomula in order to avoid the error due to difference in 126 impurity of light and heavy particles^ of refuse. Since the ash con- tent in different particles of any given coal varies directly with the specific gravity, this method of computing qualitative efficien- cy will give approximately the same figure as would he secured hy the Drakely method if a complete specific gravity analysis were made on each product and compensated values computed for the increments i of different densities in the refuse retained in the v/ashed coal. To apply the Drakely formula in this manner would he laborious in the extreme, and its use in commercial practice would he impracti- cable for that reason. Use of the ash reduction for this purpose, hov/ever, makes the desired adjustment automatically. The standard yield is determined by the sink and float method because no other method is available for fixing this point. This requires a complete specific gravity analysis of the raw coal only. The two factors, yield efficiency and qualitative effi- ciency, are combined by taking their product rather than their nu- merical average because each of these factors affects the value of the operation independently of the other; that is, if the ash re- duction approaches zero, althou^ the yield may he up to the stand- ard the efficiency of the operation approaches zero. On the other | hand, if the yield is zero the efficiency of the operation is zero, | I although the ash reduction in an infinitesimal portion of washed coal mi^t he standard. In either of these cases, if the numerical average of the yield efficiency and the qualitative efficiency is taken, the Lincoln or the Delamater formula will show an efficiency of 50 per cent, while when the two factors are combined as a prodiAct the efficiency in these cases is shown correctly as zero. This 127 means that the scale of efficiencies runs from 0 to 100 while when the general efficiency is taken as the average of the yield effi- ciency and the qualitative efficiency it runs from 50 to 100* In the experimental washing tests which were conducted in the laboratory where equipment and time were available for making a complete study of the operations, specific gravity analyses were made on samples of the raw coal, washed coal, refuse, and in some tests cases of intermediate or middling products. Screening^on all the products of the specific gravity analyses then completed the data to show exactly what disposition was made by the washer of each type of raw coal particles as regards density and size, which are the two most important factors affecting the separation of refuse particles from coal particles. 128 CHAPTER VII COAL WASHING TESTS 25. Outline of the Experimental Work. It was not the in- tention in this study to go into the principles of the hydrosepara- tion of minerals with an investigation of settling ratios, rates of falling in water, etc. , as that ground has probably been as thor- oughly covered as the needs of actual commercial practice justify. The object was rather to examine a number of typical coals, partic- ularly coals which have been found difficult to wash, to determine to what extent these coals can be improved by washing and to deter- mine, if possible, what are the characteristics of the non-washable coals which make them difficult to wash. Washing tests with jigs and tables were made in the lab- oratory on samples of coal from the Illinois No. 6 seam at Herrin, from the Bon Air seam at Bon Air, Tennessee, from Beds ”C” and ‘’D’' in Clearfield County, Pennsylvania, from the Eagle seam of the Kanawha group at Ramage, West Virginia, a.nd from the Indiana No. 3 seam at Terre Haute. Of these five coals the Tennessee coal and the West Virginia coal are classed as distinctly non-washable and the Pennsylvania coal as difficult to wash at jigging sizes. 26. Equi pment Used in Experimental Work . The coal washing jigs installed in the iiining Laboratory of the University of Illi- nois are a Stewart jig with a 8* x 1-^' P^'H, a three compartment New Century (Elmore) jig with the differential eccentric, which gives a rapid down stroke and a slow upstroke to the piston, and a two com- partment Kartz jig similar to the Luhrig nut coal jig illustrated in Fig, 8, This jig, shown in the photograph, Fig. 22, was used 8 151 for all the laboratory jig v/aahing tests of this study. The pistons are actuated by simple eccentrics which give equal up and down strokes. The length of stroke and number of strokes per minute are adjustable. The height of the final washed coal overflow gate and of the overflow from the first compartment to the second compartment are adjustable, so that the thickness of the bed of coal maintained on the screens may be varied by the operator. The refuse discharge gate is of the pot valve type consisting of an opening in the dis- charge side of the jig box just above the screen. Inside the jig box a vertical half cylinder, which covers this opening, extends down through the coal layer of the bed and into the upper part of the refuse layer. The refuse passes under the lower edge of this cylinder and out the gate, but the coal cannot w'ork down through the heavy refuse to enter the cylinder from below. The height of this cylinder is adjustable so that the thickness of the refuse bed may be varied. The rate of discharge of refuse from the jig is regulat- ed by hand by varying the size of the discharge opening. Each com- partment, 7” X 15** in screen size, is provided with one refuse dis- charge valve, A feldspar bed may be used in either or both compart- ments. The raw coal is fed to the jig by shoveling into a chute from which it runs by gravity into the first compartment of the jig through an adjustable gate, by v^ich the rate of feed may be regu- lated. The table washing tests of this study were made on two experimental concentrating tables in the Mining Laboratory of the University of Illinois and on a commercial size coal washing table at the Testing Plant of the Deister Concentrator Company at Fort Wayne, Indiana, The two laboratory tables are shov/n in the photo- 133 graph Fig. 23. The table in the foreground is a Butchart ta,ble man- ufactured by V/. A. Butchart, Denver, Colorado, and the other is a Deister-Overstrom table manufactured by the Deleter Concentrator Company, Fort V/ayne, Indiana. The laboratory Butchart table is 7* 6*’ long by 3’ 0” wide, giving a deck area of 22^ square feet. The Deister-Overstrom is 7* 3" long by 3* 3“ v/ide with a deck area of 23^- square feet. The special feature of the Butchart table is the shape of the riffle which has a curved portion in the middling zone so that the heavy material moving along the riffles toward the concentrates discharge edge has to climb in this curved section against the trans- verse inclination of the table deck. This facilitates the cleaning of the concentrate, vfhich in coal washing is the refuse, and makes the line of separation of refuse from the coal more stationary as the coal cannot climb against the transverse flow of wash water. Also by moving the load of refuse farther up on the table toward the wash water launder, it increases the effective area of the clean- ing zone and increases in a measure the capacity of the table. This effect is most apparent in the treatment of coals containing a large proportion of refuse. A similar effect is secured on the Plato table, manufactured by the Deister Machine Company, by making the concentrates climb against an inclination of the surface of the deck in the middling zone corresponding to the curved riffle portion of the Butchart deck. The Deister-Overstrom table, which is the other machine shown in the photograph, secures an increased capacity and cleaning area by the diagonal deck feature. The deck of this table is shown in the drav/ing, Fig. 24. The raw coal feed box and middling dis- Fig, 24A- Coal Washing Table Showing Special Equipment Used ^ - 136 charge are at opposite corners on the long diagonal so that the middling particles and unseparated coal and refuse particles have to travel the maximum distance before being discharged as middling. As Bhowi in the illustration , Fig. 22, the tables in the laboratory discharge their products into galvanized tanks. From these tanks the v/ater and coal are piped through the floor into set- tling cones from which the settled coal and refuse are drawn off into steam heated drying pans for sampling and v/ei^ing. The tanks are divided into compartments so that three products can be made in the Butchart table tests, and four can be made in tests on the Deister-Overstrom table. The division points between the various compartments are adjustable so that any desired separation nay be made. In order to make an intensive study of the disposition made by the table of the various kinds of particles as regards ash and sulfur content these two tables were equipped with a series of spouts along the refuse and the coal discharge edges to guide the discharging material into a number of separate sampling cans or com- partments. The arrangement of this special equipment on the Deister-Overstrom table is shown in Fig. 23. The coal and refuse discharging around the side and end of the table may thus be divided into twenty products varying in quality from the cleanest coal to the cleanest refuse. The divisions were made closest together around the middling corner of the te.ble because this is the region in which the separation between coal and refuse is made. Somewhat similar equipment was used by Richards^ in making a study of the ^Text book on Ore Dressing, p. 343. •». 1 ... • nzoin-zn 0 Ts'O y ^*4***S^, - . - . k .. i.^i, J; - <51' a.’* ■ ■‘l i~. 1 ' ':.< In* c>;jXaJ •ta.**' ... ’ . • -. V* 'i ■ . ' 2'£ « .0 iv^ c X ••■■■, i "ir:i :i": .!* • *' •> * /• ./ - V - J - a - ... « • « -"f' r. .1 •T.-Oria ■V ''' ':'. X •'1/.' ’.' I a' . T J’o:; 1. ‘If, xj.vl *• * i.v'.j’on ' ^ .'y • * D ot . I a a • r fS 'V *• . > w ■■ - * O '. •7, :^ .)v. '. 4*t £' . f * . i ' > j-'V' J,,.? 4J A ^ « V Cto't' U--J :co ^ailJ -die ''': iX ms -10. £ bt>: :j . J : oa -V' : ^roo^err}/. ’>3;?i:Trii>' C'£ ••■* ^ rii.r ■xi c*' Xifis— , UM " ■*«■ ci w‘-.: u^T I . . . • ■ *>cf , 1. f . IX crj <•' X ! ',rj ! ' c>fl- . ■ ■STO'x ,? c'>;s / ~ 0/ i vji. , eifj iX .-.n • ' ■- * 'SC .rrxxf- r - ^ ic^ v'%•'J^ r'^5,+ fr; .:-! ^yij^cr. Q.f -rcib-s- nl ■ " * 'ic> r„-.-ti^ Drti lo r. P ■ IS? r);-. ox o;-x- ■ 0 tI^ X : 00 6iO _’...- s . C' X ^ t X i ' W , f i .* '£- -..••10 ■. • 'XOc^-.:;;-,, . el'll Xr.i'Trtj; - Y ‘ X:,iiv.':o.«ib is» - - i:. X V • X :jra^ :■ 'to : T < '• .Yf.^*-. .j/ ; ;x ‘met: ■’. ^.; : L^cj o: i ,f , * . ij i. / > : : .■ * *r . ..-. - <:l -i yi / ax;.:j - .i: .iijx;X t -'X '1 o , ' ■•* ■ .;.'i:' orr^,. ■ OX ''.O *f‘D.Tj.3.' •; ;)•'■*■ irtO',’: ' vXx ■ 'i; ni ' 3 j. . •▼ c_X p o 'i ■ 'cXri ’X CX::.*^ . .' ••■: c :* .X 2 0 T ■' ' :': n-r •'■' i.. /if-v Q '' . ‘’'Irt v*’»Ji:-." 'y . O 'si I.::, ^•: ; arfx nl nlji' e.::tf "X j-iX lo iorrioo 7 i’iXpoxar' Or~f„‘ b/nro*! -'■' • ' ."X ai b.;-"'. X,..uo naov.’X^^ > rloirir ni .... ... r . " ' ^ ; ,£.x i)d8i.' :;.cwr ■‘rttJirf^iL'pr jj'' / '■,^‘C ... *c'u-*''S[I ©*xO no ioco' 137 operation of the Wilfley table on a quart 25 galena ore. C' 27. Comparison of the Work of the Experimental Table With That of the Commercial Size Table . In order to determine what value ni^t be attached to the results secured in tests on the laboratory size tables, tests on duplicate senples were made on the full size table at the Deister Concentrator Company’s testing plant and on the Deister-Overstrom table in the Mining Laboratory. These tests were made on an Indiana coal crushed to one-fourth inch maximum size. Results secured with the full size table are given in Table 12 . TABLE 12 Results ! Secured by Trei atment of an Indiana Coal on the Commercial Size Deister-Overstrom Table Weight Per cent Per cent Per cent Product pounds of feed ash sulfur Raw coal 6444 100.0 16. 5 3.85 7/ashed coal ( Coarse) Sludge^ 5238 81. 5 6,9 3,38 374 5,6 32.3 2. 26 Refuse 832 12.9 63.7 5.9 5 Sample of washed coal including sludge Same calculated from sludge and coarse 8,6 washed coal 8. 55 .05 check Rate 5;^ tons per hour. The results of the test on the small laboratory table were given in Table 4 end Rig. 5 of the chapter on coal washing principles. The separation, which most nearly duplicated the work ^The Sludge is fine coal and dust draining from the v;as?ied coal as it is elevated to the storage bin by a dewatering drag con- veyor. 13 8 of the large table, was between samples 13 and 14 giving a yield of 85.7 per cent of washed coal with an ash content of 8.7 per cent and sulfur content of 3.33 per cent, as compared v;ith a yield on the large table of 87.1 per cent of washed coal v;ith 8.6 per cent ash and 3.42 per cent sulfur. This indicates that the laboratory size table will do about as good work in ash and sulfur reduction as the commercial size machine. The capacity of the small machine, hov;evsr, is slightly smaller in proportion to its size than that of the large machine. The tonnages treated in the laboratory tests varied from 1200 pounds to one ton per hour, while the commercial size table, which has approximately five times the deck area of the experimental table, handles from five to eight tons per hour. There is also a difference in the size of material which the tv;o tables will handle, as the large table will treat successfully a feed crushed to a max- imum size of one-half inch round hole, while the largest size that the laboratory table will handle efficiently is three-eighths inch. 26. Tests On Herrin Coal . The sample of Herrin coal as received at the laboratory consisted of three inch screenings ana- lyzing 12.2 per cent ash and 2.7 per cent sulfur. The visible im- purities consisted of pieces of pyrite bands and lenses as much as one inch in thickness; thin hard shale bands, of the kind that do not disintegrate in water; a small amount of fine clay; thin plates of pyrite in joint fissures and an unusually large showing of cal- cite and gypsum in thin flakes. Tab!|.e 13^ showing the bands of impurities occurring at ^Analyses of Coal, U. S. Bureau of Mines Bull. 22, p. 513 139 two places in this mine where face samples were taken by Bureau of Mines engineers will show the kind of impurities that hare to be washed out. TABUD 13 Sections of No. 6 Coal Bed at Herrin, Illinois, Big Muddy No. 7 Mine Section A Feet Inches Section B Feet Inches Roof, shale. Top coal (a) 1 7 — Coal 0 7 0 6 Su Iphur ( a ) -- — 0 Mother coal 0 i — — Coal 0 7 0 8 Shale, regular parting • • — — 0 1/8 Mother coal 0 1/8 — — Coal 0 11 1 3 Mother coal - - — 0 1/8 Shale and mother coal 0 Coal 1 8 1 3 Sulphur — 0 1/8 Shale 0 Vs — Coal . . . — - 1 6 Mother coal 0 1/8 0 1/8 Coal 1 4 1 7 Blue band (a) 0 1 0 2 Coal . . 2 0 2 0 Floor, fire clay. Thickness of section 8 9 7/8 8 111- Thickness of coal sample 7 1 7/8 8 9f Of the 2.7 per cent of sulfur in the avera^ge raw coal used for the tests 0.8 per cent was in the organic form and 1.8 per cent was in the pyritic form with a trace of eulfa.te sulfur. Sam- ples crushed to finer than one-ei^th inch and ca,refully ha~nd pick- ed, using forceps and a magnifying glass, to discard all particles showing a trace of impurity on the surface, still contained an aver- 140 age of 4,0 per cent ash and 1^0 per cent pyritic sulfur. The mine from v;hich this coal came is on the edge of the low sulfur coal basis of i’ranklin and Williamson Counties as mapped out by G. H. Gady^ who designates the mine samples as averaging be- tween 1,25 and 1.50 per cent sulfur. Car samples and washery head samples taken at this mine at different times varied from less than one per cent to as high as three per cent. in sulfur. This shows how erratic and uncertain is the sulfur content of this coal. This, ac- cording to the reports of coke oven and gas plant operators who have attempted to use Southern Illinois coals, is typical of the Franklin Williamson County low sulfur coals. The greatest advantage of wash- ing such a coal would be to make the ash and sulfur content more unifo rm. For the washing tests the coal was crushed in toothed rolls to pass a one inch round hole screen and separated at one- fourth inch size. The over-size i-** - I” in size was washed on the experimental jig described above, and the under-size 0“ - in size was washed on the Butchart table. Results of these tests are shown in Tables 14 and 15. ^ines Producing Low Sulfur Coal in the Central District, 111, Geol. Survey Bull. 23. 141 TABLE 14 Jig Washing Test on Herrin Coal at i” - 1” size Product Weight pounds Per cent of raw coal Per cent ash Per cent sulfur Raw coal 385.0 100.0 11.0 2.70 Washed coal 344.0 89. 5 7.7 1.89 Middling 5.0 1. 3 36. 5 5.85 2nd Hutch ( Slud, ge ) 8.0 2.0 16.2 3.77 Refuse 18.8 4.9 48.5 10.90 1st Hutch 2.0 0 . 5 80. 2 2. 69 (Pine refuse) 98. 2 Loss 1.8 TABLE 15 Washing Test on Herrin Coal; 0** - - 4 " size; Eutchart Table Product Weight Per cent of pounds raw coal Per cent Per cent ash sulfur Raw coal 205.0 100.0 14.2 2.70 V/ashed coal 161.0 78. 5 7.2 1 . 85 Middling 16.0 7.8 19.8 2 . 56 V/ashed coal & Middling 177.0 ^ 86.3 8. 1 1 . 90 Refuse 13. 0"^ 9. 5 72.1 10 . 75 Loss 4.8 ' In these tests the jig showed a washed coal yield of 89. 5 per cent v/ith an ash reduction of 29 per cent and a sulfur reduction of 30 per cent, vhile the table showed a yield of 86.3 per cent with an ash reduction of 43 per cent and a sulfur reduction of 30 per cent. The raw coal feed on the two tests was not identical in ash content so that the tests are not perfectly comparable, but taking this fact into consideration the degree of separation secured in the tv/o tests is about the same. The greater reduction in ash 142 and the lower yield in the tatle test are exj^lained by the higher I ash content of the feed. The efficiencies as compared v^ith sink / and float separation taking float on solution of 1.35 specific grav- ity as standard v/ashed coal, are 67 per cent for the jig test and /j 69 per cent for the table test. / A complete specific gravity analysis of the 0” - raw ^ coal is given in Table 16. ^ TABLE 16 Specific Gravity Analysis of Herrin Coal at 0” - size Specific Gravity Per cent of - B&jnple Per cent ash Per cent sulfur Lifter than 1.30 73.35 4.64 1.72 1.30 to 1.35 8o74 11.27 2. 14 1.35 to 1.40 4.93 17.78 2.39 1.40 to 1.45 1.82 20.32 2. 52 1.45 to 1.50 0.39 24.60 2.62 1.50 to 1.60 1.12 29.90 2.80 1.60 to 1.80 2. 13 49. 53 3. 43 Heavier than 1.80 7. 52 84.04 13.63 In order to more easily interpret these figures, graphs, Big. 25 and Fig. 26, have been drawn to show the distribution of impurities in the coal according to density. Beginning at the top, the ordinate line is divided into parts proportional to the percent- ages of the different specific gravity products beginning with the lightest. The total length of the ordinate ajcis thus represents the total weight of raw coal 100 per cent. Midway of the ordinate for each specific gravity increment of the sample its average ash or sulfur content is laid off as the abscissa. Vertical lines drawn throu^ these points gives a graph, showing the distribution of ash or sulfur in the raw coal, and the area between the graph and < ( l -i' « O’! r i! I 1 i 1 ti ! \fhrc^nt 'Yi\€>ld 1 145 the axis shows the weight of ash or sulfur in the sample of weight 100. The mean abscissa is the raw coal ash or sulfur. The purpose of this curve is to determine where to make the separating line aA, Fig. 26, between the refuse and clean coal in order to obtain best values for *‘Y" yield of clean coal and for “X“ ash or sulfur content of clean coal. Obviously there is a func- tional relation beWeen *'X” and Plotting the curve of X^, X. Y for ash and sulfur gives Yn the curves of Fig. 26, which show what yield corresponds to any re- quired ash or sulfur content and what ash or sulfur content may be secured in any proportion taken as clean coal on the basis of sink and float or theoretically perfect separation. These theoretical yield curves are cftlled the ‘*Float-ash curve and the float- sulfur curve’*. The float-ash curve on the Herrin coal shows a yield by sink and float separation, of 91 per cent of coal of an ash content equal to that of the washed coal of the table test, namely, 7.2 per cent. As the washing test yielded 78. 5 per cent of v/ashed. coal this shows a recovery of or 86.2 per cent of the good coal of 9 1 this quality present in the raw coal. Comparing the yield of washed coal plus middling, making a washed coal of 8.1 per cent ash content 86 3 with the float-ash curve shows a recovery by washing of or 93.8 92 per cent of this material available in the raw coa,l. 29. Bon Air Coal. For the tests on co8-l from this seam a sample of run of miine coal from the Eastland Mine of the Bon Air Coal and Iron Company was used. This sample as received at the lg.boratory in Urbana was of rather fine size* 89.5 per cent passed throu^ a two inch round hole screen. Analysis of a moisture-free 146 sample showed a sulfur content of 4.87 per cent and 15.5 per cent ash. Notwithstanding this high ash and sulfur analysis, visual examination showed very little free dirt. This indicates that the impurities are intimately mixed with the coal. The object of the experimental work on this particular coal was to detemine to whst extent the sulfur content can be re- duced. Several years ago attempts were made to loY/er the sulfur in this coal by washing with jigs, in order to produce a more suitable coal for the Bon Air Coal and Iron Company’s coke ovens at Eastland, but these attempts were unsuccessful. The experiments made at Urbana constitute a second attempt to produce a low sulfur coal by using newer and more improved methods of washing. The results of screening tests given in detail in Table 17 shows the sulfur to be very evenly distributed through the sizes and that nothing is to be gained by screening out either the coarse or fine sizes. Sink and float tests made on these sized products and on original raw coal samples crushed to one-half inch and one- fourth inch maximum sizes, using zinc chloride solution of 1. 45 specific gravity, all showed very poor results in the way of ash and sulfur reduction, the float in every case analyzing three per cent or more in sulfur and over eleven per cent ash. This shows conclusively that due to the high residual ash and sulfur it is im- possible to make a hi^ grade coking coal by washing this material. , I ' 1 n>- . II ‘ ^ -irfj i wje!f . V '* f.' -iii.-tl ^i:,} , 'ziL' -:'r‘ ^' oila .-.rii^sir" •< , ' O’j 'v ■•*;•' ; ■■::x ’.'i r ■ i . , j ■, •■i-i n T-r'i:**: ! .• •■ r*? .;-. . C. :* lo io»:, ;P ';riT -wrj! ' ' .'.-.0 *.iii C^J u:/ i^oo ’-. .'Llun o.ii -if*’ oX uJ . o;:>: J t<»v< . ,r- Dl^'. J '. :•; o-iv.. 'Di:' 0 ':q < T^^-xo ‘ .uJiXt xv.^ 5 Pi 'iswW •>; ■ -OOG , J i*i -.ryvo o::Ci'- : ' Y/’.i^'.fiGC^' r il &ii> 1 • •;.;> -xi^ ''.o'l \ V lol I>.:oo j|^l w* •. '*'•; K.t . -i.i, «,. ’ .E;»G:>ifQi;j Sir vj. 9e«Jfw ^ '.. : KCi .-.I b ; 3 vr;/xiJ?rroo " I '.r. - * ^ I c coc^j:' 9vo":GJiJt G'loa ^ n : *rnr»->rt tini jp I’.X ;' iV. ..I 11 =r-:- ’, Cv.pd^' 3T.i.-:';^£.''io»f Ow- nl on da.:'.'X bu. ^ ^ " %a . 0 .>O.L' 0 ’XO o.,Oi‘f:r i;.> n.r’ >LnXr .'J-rlb o:ii% ': ;: ^ -■ "X :X - .po Oc* ivT -j •-jIjxGuiO /.•‘..''G IsnX: ii'j no on ; ^ ♦ . “io ncis /I’ • jbxToXi'P oaivT: , ,n.,i'" :;: * . .rGi-.l i"J-rj:ol }f :^.-: r • -nv/ b:id rl «0:i.O','r: v^o;* Oj .-c'Cft .* ,x-iv”n'b g^ iXo-bir* | '<•- t f:X;:v,j.^. '. ^ *cp ni J'noX': ^ i-j’tXus f' Gui'0,1in . Xlf*' . b*^ J ;00 •29'^ il»VOX*' Tf*'w b fl. •Xu'i'XjjT :'i 9JXi’. 'i X 1f>n ■-.;1 clJ .Xi i£/ifUG Gf. ' Xi't-x LiiUbik6‘i .'•■ .in opj oj bj'O J :-riJ vX« .'i jnXonoo i; ;il''J XX ui ^ vffiPtjnw I.:o» jiniioo ni- i:' o •■ . ii bOOp 147 TABLE 17 Screening Test on Bon Air Run of Mine Coal as Received Size Weight pounds ^ of total % sulfur On 2“ round hole 5. 24 10. 5 4.44 On 1” round hole 14. 52 29,3 4. 46 On -h** round hole 11. 40 23.2 4.93 On round hole 8.30 16.7 4.41 On l/8*' round hole 4. 56 9, 2 4. 41 Through 1/8“ round hole 5. 50 11.1 4.20 Head sample 49. 52 100.0 4. 87 Sink and Float Used TABLE 18 Tests on Bon 1,45 specific Air Coal Solution gravity % sulfur % sulfur Sink % float in float % sink in sink 1" - 2« 92. 6 3.34 7.4 18.80 - I” 88. 5 3. 12 10,9 17.08 Xii 88. 0 3.07 12.0 14. 40 1/8“ - 1“ 87.6 3.17 12.4 13. 37 0« - 1/8” 82. 5 2.99 17. 5 9.95 0« - i” ( crushed) 90. 5 3.22 9. 5 20.7 0» - ( crushed) 92. 1 3. 51 7.9 21.7 As a visual examination showed very little visible coarse pyrite and these sink and float tests indicated an advantage in the fine sizes, of a higher yield of float coal and cleaner ref- use in the sink, the entire sample was crushed to a maximian size of three-eighths inches before washing. Table 19 gives the results of a complete specific gravity analysis made on the raw coal at this size. The float-ash and the float- sulfur curves are shov/n in Fig. 27 i i V I r ♦ fi i I *< o: ' i c. a Fe^rce^nf 'F/ O 0 •H 0 fi c O -P 0 0 r-r d o o fn •H <: s:J o pq • 'CS W 0 ^ 0 tH O ■P cd 0 rQ rH ^0 • !>■ CO •d 0 0 d 'h Vh fH o 0 CO O Oi • • sj« to ^0 •d 0 Jh 0 d Ch «h Vh d O 0 A •d 0 fH 0 d tH I — I tH d O 0 lO lO o • • H to CM 0 d CO O to • • • H to r-l CM rH 0 0 tH tH O o 0 rQ CM CO 0 0 O > u d tH iH d 0 c- o • CO *d 0 0 tH tH o o> CM •d 0 fH 0 d tH tH iH tH d O 0 >- • • ^ CO r- fn d tH iH = = = d 0 l> iH to 0 > • • • • CM CM CM to rH CM CO 0 iH P« CO 0 d d P< d •H O iH tH U 0 i> o CiO fj •H H ■ — I o p ci 3 o p 0 . 0 0 p f> o 0 ^ ^ d p wS d fn •H tiO H d d -H 'd d d 0 o d d p p c 0 rd 0 02 •H Pi 0 0 0 •d 0 -H 02 0 rd 0 Eh 0 o d •H (U t> . »• , 1 ! H M. 162 Results of tlie two jig tests on Clover Run coal are given in Talles 26 c.>nd 27. The low efficiency secured in the second test v/as due to the fine material present in the unsized feed. Appar- ently the material below one-fourth inch ring size was not handled efficiently in this test and the sink and float tests shovi^ed in this size a very complete separation with a very small middling product, a high yield of float coal and a large reduction in sulfur content. As compared with these sink and float results, the separation in the jig v/as poor. On the other test, where the rav; coal was screen- ed at one-fourth inch and the fine coal and the coarse coal were washed separately, the efficiency of the jig on the - 4 “ - 1 “ feed was 63 per cent as compared with an efficiency of 44 on the 0“ - 1 ” feed unsized. The average sulfur content of the washed coal, fine and coarse combined, was 1.93 per cent with a yield of 74.5 per cent as compared with a 72 per cent yield of washed coal of 2.02 per cent sulfur on the 0” - 1 ” jig test. This shows a slight advantage in sizing before washing. The jig tests on this coal were not as successful in re- ducing sulfur as the table washing tests. The preliminary sink and float tests indicated that this v/ould be the case as the large sizes -i” - and - 1 ” contained a much larger percentage of material of intermediate density, between 1.35 and 1.60 specific gravity, than the finer material under size. This is the materi- al which forms middlings, pieces part coal and part refuse, which require finer crushing in order to free the particles of refuse and coal. All these tests indicate the necessity of fine crushing. In conducting the table v/ashing tests, from three to five products v/ere made for analysis in order to get as complete data 163 as possible on the separation being secured. Composite fif^res showing what the results would be if only two products were made are arrived at by combining the products as desired and calculating the average ash and sulfur content. In the table tests division of the product into four grades, No. 1 coal, No. 2 coal. No. 3 coal, | and refuse, was accomplished by dividing the material being dis- charged over the end and side of the table at suitable points as showned in the diagrams in Tables 28 and 29. By washing with the table the pyritie sulfur content was reduced 70.4 per cent in the 0” - 3/8*‘ No. 1 coal and 78.4 per cent in the 0” - No. 1 and No. 2 coal. These reductions of pyritie sulfur are large and the hi^ reduction in total sulfur obtained by washing was made possible because only a small percentage of the total sulfur in the raw coal is present as organic sulfur. The efficiencies were 74 per cent for the 0” - 'i*' test and 80 per cent for the 0“ - 3/8” test. Qn \7est Vir,c;inia Coa l. The West Virginia coal | used for washing tests was mined at Ramage, in Boone County. The | 1 sample received was taken by employees of the company who were in- I V structed to take a sample representative of a full day*s output of f I the mine. An official of the company, who was present when the s I tests were made, stated that this particular sample was somewhat j 5 hi^er in sulfur than the average for coal from this mine. The coalj was very hard and when crushed to about three inches maximum size | showed very little free pyrite and little or no slate or shale. It | contained 2.48 per cent sulfur and 6.81 per cent ash on the moisturel free basis. The mine operates in the Eagle seam of the Kanawha Group. The average of ten analyses on samples from the same seam I 164 and county by the West Virginia Geological Survey show only 0.79 per cent sulfur. ^ Po r some time past this cojal has been used by a steel company for making producer gas, the gas being used in open hearth furnaces. Recently variations of sulfur in coal from this mine have caused difficulty in using it because of the hi^ sulfur con- tent of the gas. The purpose of the work described here v/as to de- termine v^ether or not the sulfur in this coal could be reduced low enou^ to make it suitable for open hearth fuel upon gasification. In all the tests carried out the sulfur content of the cleanest coal obtained was well above the maximum figure designated by the operator as satisfactory. The cleanest coal secured analyzed 1.65 per cent sulfur. This product, more-over, amounted to only one- third of the original raw coal fed to the washer and also was crush- ed to three-eigihths inch maximum size, which is finer than is de- sirable for producer gas fuel. The sulfur content of the No. 1 v/ashed coals secured by jigging at suitable size for gas producer use, namely, 0” - was 1.98 and 2.00 per cent. These products again represented recoveries of only 84 oer cent and 76 per cent, \ \ respectively. )\t the 0“ - size a product consisting of 91.4 per | t cent of the raw coal analyzed 2.06 per cent sulfur, and in the 0“ --3/8“ size a product carrying 2.01 per cent sulfur amounted to 92.7 per cent of the raw coal. The plan followed in the examination of this coal vras similar to that described in the discussion of the tests on the ^V/hite, I. C. , , Geo graphical Distribution of Sulfur in Y/est Virginia Coal, .to. Inst. Min. £.nd Met. Br.g. Bull, 153, p* 2200, j 1919. 165 Clover Run Coal. Table 30 shows the screen analysis on raw coal crushed to three-four ths inch maximum size and Table 31 shovrs re- suits of the sink and float tests on the sized products of the screening tests. TABLE 30 Sere en Analysis, Spruce River Coal Weight Size pounds ^ of total % ash % sulfur 42 - I" 36 39 6. 83 2. 66 33 6. 28 2. 42 0” - 30 28 6. 64 2. 31 TABLE 31 Sink and Float Tests, Spruce River Coal Pro duct ^ of sample % ash % sulfur Size Float on 1.35 Sp. G. 89.5 4. 0 1.78 Middling 1.35 to 1.80 7. 5 26.8 6. 40 Sink in 1.80 2.7 47. 3 22. 21 Size Float 1. 35 Sp. G. 91.0 4. 0 1. 68 Middling 1.35 to 1.80 5. 5 18.7 10. 50 Sink in 1. 30 3. 3 49. 2 15.06 Size 0" - Float 1.35 Sp. G. 94. 6 4. 1 1.84 Middling 1,35 to 1.80 1.7 26. 0 7.00 Sink in 1, 80 3. 2 52.7 14.07 - - 1 V \ fig •if itxius: ‘ ■'(f 166 T/3LE 32 Specific Gravity Analysis, Spruce River Coal at 0» - 3/e»' size Specific Gravity Y/eight grams % of total sample ^ ash % sulfur to 1.25 2369 N 51.2 2. 12 1. 15 1.25 to 1. 30 1529 33.0 3. 68 1. 36 1. 30 to 1.35 420 9. 1 12. 43 3. 55 1.35 to 1. 40 44 1. 0 14.20 3. 36 1.40 to 1.45 43 .9 19.75 4, 38 1.45 to 1, 50 30 . 6 23. 20 4. 41 1. 50 to 1.60 39 .9 28.63 5. 25 1.60 to 1. 80 62 1.3 37.82 5. 68 1.80 90 2.0 67.27 17.95 To tal 4626 100.0 In the washing tests four methods of treatment were tried. 1. A sample of 828 pounds of the raw coal. crushed to ” maximura size, v/as screened on a quarter inch round hole screen. The oversize 0” - •¥” was treated on a coal ^washing table. 2. Eight hundred forthy-two pounds of the raw coal crushed to pass a v” round^screen was ^ treated v/ithout sizing on the jig. hole 3. A sample of 292 pounds of the rav/ coal was crushed to 3/8” ms.ximum size and washed on the table 4. In order to determine the distribution of im- purities in the coal as discharged from the washing table and to compare the results secured “by table washing coal of 0” - 3/8” in size v/ith results secured by close sizing, a. sample of this coal crushed to 3/8” maximuin size was screened on l/8” and i” round hole screens and the three sizes 0” - 1/8”, 1/8” - i”, and - 3/8” v/ere washed separately on the con- centrating tables using the special equipment for separating the product into nineteen samples. In conducting tests 1, 2 and 3, from three to five prod- ucts were made for analysis in order to get as complete data as possible on the separation being secured. Composite figures show- ^ f, Table 35- Spruce River Coal -0” 3/-^” Test 167 • Cm to O to rH '^'d -» O :R Cm Cm -P Cm • O- P A 02 0 \CN »vO • Cm d 0 rH ft; rH lr\CM tH O 0 d U d P CO CM^O c*-i 0 • • • rH 0 rOCO O d P ch 0 0 ro • d Cm 0 0 to ^ O ffi 0 P o fH rH rH CM Cm d * • P 0 o CTnO d- • o p p mcM '5^ rH CO • 'vO CO hJ iH ri tiH rH rH ^ CO CO ■s^ -p d -■ §H -d o «3 GOO C\J CO o o5 OJ "O fH 0) 'i t O ‘ • G 0 } Ch to Vj^ ^ O cvj rH O '-O CO, • rH rH CM rH 'dCO > to u G d •H 'O 'CS o rH -d o cd •H O O t:! CO o kS o CO to f-i tS G o5 'h R«>- ’LTNCXJCO'A • rH ’vO CO *00 • mrH 1T\ to 'd 0) si rH Si G 02 f(H 02 Oj O »R •CO rH O O CJNCO • O • • ^ C>-rHlr\OD 0) Jh IfN • O CJ^ rH • • ON CM lr\ u • c'5, ro ICN 1 — 1 d o o 'd 0 A 0 g d o A A fH u d rd 0 G ft d d -P 0 0 fH 0 d d G 0 ro 0 • P o 0 G O Cm O -P • d o -P 1 — 1 Cm Cm 0 • Cm ■P CT* o d 0 G 0 •H •H S 0 0 r ^ d 0 fn P 0 0 • H-> Ph 02 G d P O G 0 P •H 0 S r^ O o O ICN G ON fH''0 0 P +> OO •H 0 O 0 0 •H s CM -p Cm •H i>- d Cm P P !XJ 'A y ' Tti ^ : Table 36 - Spruce River Coal 1/4“ - 3/4" Jig Test 168 .c! OJ «3 0 > •ri CD CD 'h R 03 O 03 cc5 lr\I>-vO • • • ITN O 'M' rH PO 05 CD u cd CD CD TzJ fn 0 03 d 03 • C7N CD Ch ^ 03 « •s & Cm rH 03 « d cd -p rH -p cd Ch 03 Cm CO ^ d ^ Pi s:l • to 0 V'i '^^ro • (Js R ■d 8 rQ CH UN Cm — ! C'-vO • 03 1 1 sc: 0 0 • • UN xJ d CM CO 0 'sj- 0 CM rH u CD 03 CD o Pi d 0 d 0 += Cm d 0 d Pi d u 03 >> iH ra Cm 0 d d 0 bO U d cd 0 Cm •H Pi cd • 03 Cm Cm iH B -*rH d 0 0 d 0 rH C rQ Vi 0 Cm 0 0 0 P d 'd 0 rH H UNlTN*:^ 0 cd 0 0 d ■d 0 Cd rH • ti — ■p Pid •H 0 0 CXD • "M- • d 0 CO 0 CM iH 'cj- CJNrH rH d 0 Pi •H 0 CO CMvO CO olrN 5 U\ d CM rH -P PPJ d 0 Pi 0 0 0 rH d CD S CM -P W Ch Cm •fH CO 0 cH ^ ^ rH :o • d 03 Cm 0 0 cd 0 d rQ ■“0 rd ^sOUN 03 00 oun • cd 0 ^ • • prj ^ CM UNCX) J Efficiency, on the basis of float on 1.35 as standard washed coal, 45/ 169 ing what the results would he if only tv/o products were made are arrived at by combining the products as desired and calculating the average ash and sulfur content* TABLE 37 0“ - 3/8“ Table V/ashing Test on the West Virginia Goal Deister-Overstrom Table Product Weight pounds Per cent of feed Per cent ash Per cent sulfur Raw coal 292 100.0 6*76 2.28 No. 1 Washed coal 97 33*3 4.30 1. 65 No. 2 Washed coal 120 41.2 5. 11 1.94 No. 3 Coal 53 10*2 10*24 2*84 No* 1 and No. 2 combined 217 74. 5 4*77 1.81 No. 1 No. 2 & No . 3 270 92*7 5.85 2*01 Refuse 15 5*2 30* 57 8*90 Loss 7 2. 1 No. 1 Washed Coal No, 2 Coal No. 3 ; V- -3 ■i » 170 TABIJi) 38 O'* - 1/8" Table Test Spruce River Coal 36 Per cent of 0" - 3/8" Eutchart Table Sample Weight % of feed % ash % sulfur. Product Grams Cum* ^ Cum.. ^ Cum. Section No. 1 9525 57. 30 57. 30 6. 67 6. 67 2.03 2. 03 2 SS5 4. 10 61.40 4.9 5 6.44 1.82 1.98 3 845 5. 10 66. 50 4. 47 6. 30 1.77 1.97 4 812 4.90 71. 40 4. 32 6. 15 1, 81 1.95 5 773 4. 60 76. 00 4. 15 6.00 1. 80 1.9 4 6 708 4. 30 80. 30 4. 23 5,90 1. 81 1.94 7 662 4. 00 84. 30 4. 26 5.80 1.73 1.93 8 664 4. 00 88. 30 4. 38 5.80 1.79 1.92 0 717 4. 30 92.70 4.95 5.70 1.91 1.92 10 616 3. 70 96. 40 7. 08 5. 80 2. 19 1.93 11 141 .90 97.30 12. 50 5. 80 3. 37 1.9 5 12 25 . 15 97.45 17.00 5. 80 4. 50 1.95 13 16 .10 97. 55 17.87 5.90 4. 50 1.9 5 14 78 . 50 98.05 23.02 6.00 5. 12 1.97 15 33 . 20 98. 25 33. 89 6. 10 6. 80 1.99 16 36 . 22 98. 47 37.94 6. 20 7. 68 1.99 17 26 . 16 98, 63 41.91 6.20 8. 32 2,00 18 49 . 30 98. 83 46.86 6. 30 8.94 2.02 19 198 1.20 100.00 65.74 7. 10 16. 50 2. 20 16,610 100.00 ' ^Cum. ~ Cumulative. JaC^ 7 f \<2.n.i~ "T^fcfd I ■i 172 TABLE 39 1 / q » - Table Test Spruce River Coal 41 Per cent of 0” - 3/8'‘ Sample Butchart Table Product V/eight Grams of feed Cura, ^ • ash Cura. 1 sulfur Cum. Section No. 1 JU 1 UM — 1 ii» M aw «w wa aw » M aw O . 23 . 06 . 06 3.80 3.80 1. 17 1. 17 3 17 5 . 45 . 51 2. 80 2.92 1.26 1. 25 4 834 2. 12 2. 63 2. 60 2.66 1. 22 1. 22 5 1891 4. 82 7.45 3, 10 2.95 1. 40 1.34 6 259 6 6. 60 14.05 3.00 2.97 1, 39 1. 37 7 3310 8. 42 22. 47 3. 00 2.98 1. 52 1. 42 G 4144 10. 54 33.01 3. 10 3.02 1. 51 1.45 9 5378 13.69 46.70 3, 50 3. 16 1.97 1. 60 10 7637 19.47 66.17 4. 00 3. 40 2. 08 1.75 11 5030 12. 80 78.97 4.90 3.65 2. 60 1.88 12 2489 6.34 85. 31 5.80 3.81 2. 20 1.90 13 615 1. 56 86. 87 7. 10 3.87 2. 34 1.91 14 1670 4.25 91. 12 9.95 4. 15 2. 60 1.94 15 1267 3.23 94,35 14.80 4. 52 3.02 1.98 16 794 2.02 96. 37 21.70 4.88 4. 49 2. 04 17 440 1. 12 97.49 31.30 5. 17 6. 32 2.09 18 230 , 59 98.08 41. 80 5, 40 8. 10 2. 13 19 779 39 , 302 1,89 100. 06 100.00 55.60 6. 34 17. 50 2.41 Cum. ss Cumulative f^rc^nf Tiisld i -• f A ' W:-n '? ■r' ) .- ‘ VI* M>k \. ’, , <■ ■; i;t:{ TiiBLE 40 - 3/8” Table Test Spruce River Coal 23 Per cent of 0” - 3/8” Sample Deis ter-Overstrom Table 174 Product '^feight Grains fo of feed Cum. ^ ash Cum. ^ % sulfur Cumr Section No, 1 1125 5.70 3.70 2.80 2.80 1. 66 1.66 2 1188 3.90 7,60 2.9 5 2. 87 1.88 1.77 3 1465 4.81 12.41 3.20 3.00 1.78 1.77 4 1252 4. 11 16. 52 3.40 3. 18 1.74 1.76 5 740 2. 43 18.95 3. 40 3.20 1.78 1.77 6 1619 5. 31 24. 26 3. 30 3. 22 1.84 1.78 7 1455 4.77 29.03 3.60 3. 28 1.84 1.80 8 1376 4. 52 33. 55 3.80 3.36 1.86 1,80 9 874 2.87 36. 42 3.90 3. 40 1.92 1. 81 10 1449 4.76 41. 18 4.00 3.47 1.92 1.82 11 iq^ 3. 54 44.72 4.35 3. 54 2.07 1. 84 12 1800 5.90 50.62 5, 40 3.74 2. 04 1, 86 13 2897 9. 51 60. 13 6. 40 4. 18 2.26 1.92 14 50 50 16. 56 76.69 7.40 4.85 2. 52 2, 05 15 5013 16.45 93. 14 10.00 5.76 2.86 2. 20 16 1288 4. 22 97.36 11. 90 6. 04 3.66 2.28 17 201 .66 98.02 18.80 6. 10 4.97 2,30 le 576 1, 89 99.91 39. 00 6.80 10.10 2. 45 30,447 99.91 _ ^Cum, ss Cumulative These washing experiments with the sink and float tests and chemical analyses demonstrate conclusively that this Coal is a difficult one to wash and that the removal of only the free dirt particles in the form of a clean refuse product v/ill result in no very ^reat reduction in sulfur. The feature of general interest in this investigation is the determination of the characteristics of this coal which render it difficult to improve by washing. That the trouble is not to be overcome by fine crushing, nor by sizing before v/ashing, ie indicated by the sink and float tests. The separation in the fine sizes under one-fourth inch is not a ppreciably better than that secured on the 176 larger sizes froia one-fourth inch to three-fourths inch, and the combined results of the tv/o washing tests, where the coal was a screened on^ one-fourth inch screen before washing, are no better than the results secured in the Jigging test on 0” - f-" unsized coal. The combined washed coal products from the Jig test and the 0” - -i*’ table washing test amounted to a total yield of 83 per cent of the feed with an ash content of 5.4 per cent and a sulfur content of 1.95 per cent, while the Jig test on O'* - unsized feed yielded 84 per cent of washed coal with an ash content of 5.3 per cent and a sulfur content of 1.98 per cent. For comparing the results of the table washing tests on sized feed v/ith the test on 0" - 3/8" unsized feed, the separation between coal and refuse was made in the 0"-l/8" test between sam- ples 11 and 12, in the 1/8" - test between samples 11 and 12, and in the - 3/8" test between samples 11 and 12. This gives an average yield of 77.5 per cent of washed coal v/ith an as?i content of 5.4 per cent. The test on unsized feed yielded 74.5 per cent of Ko. 1 plus No. 2 washed coal v/ith an ash content of 4.8 per cent. This coal is rather unique in that it is high in sulfur, but compara.tively low in ash, and that v/hile the sulfur is very re- fractory, the ash is easily removable. This is an exception to the old rule of thumb that the sulfur follows the ash. The commonest difficulty met v/ith in coal v/ashing is a large percentage of ma- terial of intermediate density between 1.30 and 1.60 in specific gravity, consisting largely of bone coal and carbona-ceous shale, which forms a middling, or secondary coal too hi^ in ash and siilfui to include in the clean coal and yet too hi^ in combustible to • - 4 •-4*> ' i . ^ I I/H : e t‘ r^nltisjtw ( 'rtl^ '-S , ■ •. ) X 0 * * 177 throw away. Hov/ever, this is not the source of difficulty with this coal. In fact the sink and float tests shov/ that there is an un- usually small percentage of this material present. Visual examina- tion and specific gravity analysis show that there is very little free dirt of high specific gravity in this coal. The sulfur must he present chiefly in some other form than pieces of clean removable pyrite. The different forms of sulfur as they occur in the raw coal are given in Table 41 below, comparing this coal v/ith the Clover Run coal. Fyritic sulfur was determined by the raethod of Powell with Parr^, and organic sulfur by difference. TABLE 41 Forms of Sulfur in Spruce River and Clover Pam Coal^ Total Organic Sulfur Fine disseminat- Coarse pyr- sulfur ed pyritic sulfur itic sulfur Name of coal % ^ of to- % % of to- % % of to- tal sul- tal sul- tal sul- fur fur fur Spruce River 2.48 1.01 40. 5 0.71 28.6 0.76 30.9 Clover Run 3. 48 0.71 20.4 0.50 14.3 2.27 65.3 As shov/n by this Table an unusually large proportion of the total sulfur is present in the form of organic sulfur, and finely divided pyritic sulfur. These facts and the very low percentage of heavy material in the raw coal indicate that the sulfur is widely distributed and that there are very few concentrations of pyrite in individual pieces sufficient tc bring up their specific gravity and ^Uniy. of 111. Eng. Sxp. Sta. Bull. 111. 178 I make them removalDle "by washing. ^2* Indiana No . 3 Coal . A car load sample of this coal was examined at the testing plant of the Deister Concentrator Com- pany. The sample consisted of screenings through a one and one-half inch slot screen. Tests v/ere made with the Deister-Overstrom table on a sample of 5600 pounds crushed to one-half inch maximtim size and on a sample of 6600 pounds crushed to one-fourth inch maximum size. Of this 6600 pounds 6400 were tested on the commercial size table at the Deister-Overstrom testing plant and 200 pounds, a care- fully taken sample of the total 6600 pounds, was treated on the lab- oratory table at Urbana. The conspicuous visible impurities in the rav; coal as re- ceived consisted of shale bands and clay with very little coarse pyrite. The shale bands were very largely of clean grey shale, al- thou^ there were also black carbonaceous sha,le and bone coal par- ticles. The sample used for the 0“ - v/ashing test carried 18,7 per cent ash and 3.92 per cent sulfur, the 0” - sample analyzed 8 16.5 per cent ash and 3.85 per cent sulfur. The specific gravity I analysis of the 0” - feed is shown in Table 42. This shov/s it | to be about an average coal as far as the proportion of the differ- j ent specific gravity increments and the distribution of the ash are l concerned. The sulfur, however, is shown to be very uniformly dis- \ tributed through the coal, the li^test fractions being very little | lower in sulfur than the heaviest fractions. 179 } TABLE 42 Specific Gravity Analysis Indiana No. 3 Coal 0« - Size Per cent of Per cent Per cent Specific Gravity sample ash sulfur Lighter than 1.25 68. 0 5.4 3. 19 1.25 to 1.30 2,8 8.9 4. 12 1.30 to 1. 35 5.4 13.4 3.83 1.35 to 1.40 3.7 15.8 3. 86 1. 40 to 1.45 2.8 20.3 4. 10 1.45 to 1. 50 1.9 24.9 4.06 1. 50 to 1.60 2. 6 29. 5 3.81 1.60 to 1,80 2.3 42.1 4. 12 Heavier than 1. 80 10. 5 71. 5 6. 14 TiiBLE 43 Sink and Float Test Indiana No. 3 Coal 0" - Size; 1.35 Specific Gravity Per cent of Per cent Per cent Pro duct sample ash . sulfur Float 78.8 6.6 3. 27 Sink 21.2 59, 1 6.40 This is the coal which was used for comparing the results | 1 securahle with the laboratory size coal v/ashing table with the work | done by the full size machine in commercial operation* | Fe>rcenT 'Y/'eld 160 min: \3ul-fu i^ 3uffur Out^ cur ve. TABLE 44 181 Laboratory Table ¥/ashing Test on Indiana Coal Heads 16.5 per cent ash 3.85 per cent sulfur Sample We ight . Grams % of feed Cum. io of feed % ash Cum. % : ash % sulfur Cum. % sulfur » 1 4509 11.6 11.6 10.20 10,20 2. 86 2. 86 2 1860 4.8 16.4 5,03 8.60 2.95 2. 88 3 2015 5.2 21.6 5. 14 7.80 3. 00 2.90 4 1571 4. 1 25.7 5. 32 7.40 3. 08 2.94 '5 , 1137 2,9 >28.6 5.64 7.20 3. 13 2.96 6 2107 5. 5 34. 1 5.77 7.00 3. 36 3. 04 7 1999 5. 2 39.3 6. 13 6.90 3. 28 3. 10 8 2347 • 6. 1 45.4 6.45 6.80 3.41 3. 12 9 1863 4.8 50i2 6.97 6.80 3. 48 3. 13 10 2554 6. 6 56.8 6.60 6.75 3. 40 3. 18 11 3015 7.8 64.6 8.20 6.95 3. 50 3. 21 12 4720 12. 2 76.8 10.85 7. 55 3. 64 3. 27 13 3421 8.9 65.7 18. 57 8.70 3.78 3. 35 14 3026 7.8 93. 5 45.05 11.70 4. 11 3. 39 15 1798 4.6 98. 1 78.00 14. 80 8.60 3. 64 16 776 2.0 100.0 58.92 15.71 15.65 3. 88 TABLE 45 Indiana 0" - Washing Test, No, 3 Coal Deister-Over Strom Table Wet wt. Dry Product pounds ^ 1 moisture weight % of feed % ash % sulfur Raw coal 6180 9.0 5624 100.0 18. 73 3.92 Washed coal 5452 18. 5 4436 77.0 7.25 3. 50 (Coarse) Sludge ( By wt. ) 315 ( By dif. ) 283 6.8 34, 80 2. 66 Refuse 1100 13.6 905 16.2 68.96 5.93 Sample of vrashed coal including sludge 9,07 3.49 Same by calculation from sludge and bin washed coal 9.00 Time 27 minutes; rate tons per hour .07 check The sludge consists of fine material in the water drain- ing from the washed coal as it is elevated to the Draining Bin (34), Pig. 33 , by the dewatering drag conveyor (17). This was sampled where it overflows the washed coal sump 16 to the overflow sump 19. 182 Pennsylvania Crusher 17 Dewatering Overflow Drag Conveyor 7/a ter 34 Washed coal Drai ning Din I I sur.ip I y Centrifugal Pump y Dorr j.hi oicener /•giieri can Pi Iter ^ ' 1 7/ater Storage Tank Fig. 33-flow-cheet Deister Concentrator Company’s Testing Plant 1 .” ] -Jt &i. ' #' t-i ■■*. -V, : U' -'rr-^ 9jtxS.nx fXtv. '■'- • ' -i'v V -: ■■' ' ' i j K . k ' 'W < .7 *u l«'V * 1 ^- : ::^* r" -ii-c r "^' ^ — "•■ --•- ~ I I ■ - i i.-ou,^> ' 4 ‘i T V i >' ■ - r*.* *A' f " ■ *» ' ^ ' *i ■ ?i:-' ukk* ^rfl.'^i«;au ' 1 t ^ItTirSu X«3 x;T ii-Jr'ao'w 't. A I - - -y^ ;;;; ' "■' -^f^, ’Vic\i ► * .. JT'. i _ • u r- — — . W ai»^ -* t ■ ;; ,,, “r-Ei X i.fl^ It ! 5 ;«.“v V r 0 # j ** | . jait' L* 1 L. ; ‘ 0 ^.. «*’, 4 *(-. ■ . ,_i ., , ■■ ^ ® * '7T Aiicoi tf-i”/) lXfTt>oopC^t^>? u I il ' . 1 ?: scHHarnaHEsesf^ ■ . )• M 183 The size of this material in the 0“ - test is shovm by the screen analysis Table 46. TABhE 46 Screen Analysis of Sludge Size Per cent Per cent ash On 1/64“ Through l/32“ 8,2 25. 1 On 65 mesh Throu^ V64« 18.2 28.1 On 100 mesh Through 65 mesh 21. 5 28.8 Through 100 mesh 52. 1 To tal 100. 0 34,8 The loss on the various laboratory tests consists of similar material which overflows the settling- , cones and tanks in the laboratory. This product varies in amount and composition de- pending upon the nature of the raw coal used, the type of washer used and the method of handling the coal after washing . The sludge from this particular coal wa,s exceptionally high in ash be- cause the raw coal contained a large proportion of clay. Analysis of sludge samples from two other coals are given in Table 47, TABLE 47 Ash Content of Washed Coal Sludge Samples Coal used Washer used Ash content No, 6, Herrin, Illinois. Campbell 15. 5 Ohio, Brier Hill. Be i s ter-Overs trora 13. 5 The sludge is ordinarily higher in ash than the coarse washed eoal, but quite often lower in sulfur content. to n. ■ ’ ''•• t' f’ i i fri Cil*I •i rl •■■%■ il./ i.i- 184 The two washing tests made on the large table show an ash reduction of 62 per cent and a sulfur reduction of 11 per cent on the 0*' - -i" coal and an ash reduction of 58 per cent v;ith a sulfur reduction of 12 per cent on the 0“ - -i’* coal. This shows very good work in the removal of ash, but very poor results in sulfur reduc- tion. This is a coal which is very amenable to v/ashing as far as the ash is concerned because a large proportion of the ash is in the form of clean shale bands, v/hich are easily removed. The sulfur on the other hand is very difficult to remove. Table 48 shows the forms of sulfur in the raw coal and the washer products, TABLE 48 Forms of Sulfur in Indiajia No, 3 Coal Product To tal sulfur Pyritic Sulfur Fine dis- seminated Or S' ganic ulfur /*> ef fe> of to- tal Pyritic sulfur % % of to tcol 0« - raw coal 3,85 1,99 52 1,43 1. 86 48 0“ - washed coal ( coarse) 3, 38 1,39 41 1.99 59 0“ - -i-’* washed coal including sludge 3,32 1, 40 42 1.92 58 0“ - raw coal 3,92 2. 13 54 1. 48 1.79 46 0« - !■" washed coal ( coarse) 3. 50 1,4G 41 2. 04 59 0“ - washed coal including sludge 3.48 1, 53 44 1.95 56 Average raw coal 3,88 2.06 53 1.45 1.82 47 Fine disseminated pyritic sulfur is a comparative term which vms used in this work to designate the pyritic sulfur occurring in fine particles disseminated throu^ the coal to such an extent that it cannot be removed by any practicable mechanical process. It is ‘ •<2*s£! ' I D J _ . -'1-. j .'r-fr r‘ I *- I 185 arbitrarily defined^ here as the pyritic sulfur in the coal which floats on a solution of 1.35 specific gravity out of a representa- tive sanple crushed to pass a quarter inch round hole screen. This shows that an unusually large proportion, 55 per cent, of the sulfur in this coal occurs in the organic form, v;hile the Clover Run, Spruce River and Bon Air coals showed only 40. 5, 20.4 and 24.0 per cent, respectively, of their total sulfur in organic form. In the Indiana coal the organic sulfur and the fine disseminated pyritic sulfur combined amount 90 per cent of the total sulfur in the raw coal. This eliminates the possibility of removing any appreciable percentage of the sulfur from this coal. These tests shov/ed a concentration of organic sulfur in the washed coal due to the removal of inorganic mineral matter. This is a condition which might be expected to result in any coal washing operation v^ere an appreciable amount of shale or slate is removed as refuse. This coal, however, was the only one examined with which such a result was actually secured. The raw coal con- any tained a larger proportion of clean shale than^other used in the tests. Of the two tests the 0” - run showed the larger yield of washed coal by 4.5 per cent. This ma^r be explained as due to the higher percentage of ash in the raw coal used for the 0*' - test. As this feed contained 2.2 per cent more ash than the O’* - :i‘* feed, it is necessary to remove approximately four and a half per ^Distribution of the Forms of Sulfur in the Coal Bed, - Ynacey & Fraser, Univ. of 111. Sxp. Sta. Bull, in press. i i c i I i ■V i 186 cent more refuse in order to produce the same quality of washed coal. This indicates that crushing the coal to one-fourth inch maximum size did not result in any better separation on this coal than was secured by washing at 0” - size. The efficiencies secured in the tests, taking float on a solution of 1.35 specific gravity as standard washed coal, are 85 per cent for the 0" - size and 86 per cent for each of the two tests on 0” - coal. I 187 CHAPTER VIII CONCLUSIONS 33. Sulfur Re due tion » The washing tests showed reduc- tions of total sulfur content in the No. 1 washed coal product vary- ing from a minimum of 11 per cent with the Indiana coal to a maxi- mum of 63 per cent with the Clover Run coal washed on the concen- the trating table. Tests on^five coals examined showed great variation in sulfur reduction. Table 49 gives a summary of the results se- cured on the different coals by the different methods of v;ashing used. The Clover Run coal which showed the largest reduction in sulfur contained the smallest proportion of its sulfur in the organic fom. In the size at which the maximum sulfur reduction was secured it contained a comparatively large amount, 6.8 per cent, of material heavier than 1,80 specific gravity and analyzing 23 per cent sulfur, while the proportion of natural middling between 1.35 and 1.60 in specific gravity amounted to only 12.6 per cent. The Indiana No. 3 coal which was the most difficult of 1 the five to wash as regards sulfur removal, contained 53 per cent | of its sulfur in the organic or combined form; while the Bon Air | coal also difficult to desulphurize, thougih comparatively low in | organic sulfur, contained most of its pyrite in the form of finely | divided particles disseminated through the coal. As received s.t ! the laboratory, this coal, although it contained 4.87 per cent sul- j fur and 15.0 per cent ash, showed very little free visible impurity*! The sink and float tests show that the li^test material separated out, namely, float on solution of 1.26 specific gravity amounting I 0} +3 (n 0) E-« fcO •H Oi aj 0) -P •P ON CO o o (H •■-1 ^ -C-5 cc5 O • Eh 'O H -P Pi rH G G cd 03 -CM rOCM CM CM CM CM lr\ vO ITN vO CM CM CM CM ^ 1—1 I — I rH rH I — I I — \ I — I r— I O OCO CM CM UN CM ONOO •^C3D C^UnC>- OnnO UnUn CXD O rH CJN • • • • o rH cjncm m rH O rorn • • • • • rH rOmroCM CM «H rH CM CM rH CM CM ro mm mcjNONNOUNo o • ••••«• vOsOvOnOOO CJN CO CO l>~CO CO C?NCO UN'^ (JN o • • • • NO rHCO t>- CO 0X0 CO CM CN-CO rH t>- • • • • • CO CM mt>-UN CO CTnCOCOCO o CM CM c>-co CM m m m CO CM m m ^ mvo CJNUN O t>- CM CM ^ rH oDcocoooomm C^nO o o o >=d- U\CM CM CM CO coco CO UNCJnOCO O mCM rH UN CM CO r — I I — I r o o CO i>- OnO UNmCM rH rH mmmCM CM rH rH rH rH CM rH CMrHmmm UnUNCJnOnnO O O O UnCn-OUnUn OmOUNCO CSNCO NO CM CM UN m CO Cn-OO UN l>-CO NO sj- •'ch mNO no m rH vo l>~tN-COCOUN O-mCN-CO t>- O 0(>-t>-t>-CO OvO 5N- C ' GO CO CO U\Un CM CM mmm rH CO CO CO I rH ^ S rH I \ = rH O mmmrH = rH I I I I Nt I O O O O rH o mOOCONO rH un'^ '^UNm mmcM CM CM CO m rH mms rH O O O rH O ONC O CM UN UN ^ CM CJNCOCO CM CM m m m 'chco CM ^ fO CO (Hi — I I — I I I I I I o o o o o fl) 0)0) (Ucyo© G)dy« t> t> > Pi Pi G G G 0 0 0 0 . ( — 1 fi fi fi (fi 0 0 0 ^ 0 Pi Pi Pi mm<^ Pi <13 <13 03 03 • • • !> I> !> > 0 0 0 •H -H -H m fifififi ■H fi\ <13 <13 03 03 c G G C 3 0 0 0 3 3 3 G G P ' — G -rH •H -H Pi Pi U CM Pi TcS xJ Pi Pi Pi rH Pi G G G CO CO CO — ' jO IH HH M rH CM m ^ unno ctn o rH cm m un^o c>-oo rH rH rH t — I rH i — I I — I i — I I — | 188 189 to only 16,3 per cent of the original raw coal, contained 1.28 per cent of pyritic sulfur, and 7*8 cent ash. This shows that a part of the pyrite and the ash is distributed through the lightest coal , The West Virginia coal from which it was also difficult to remove the sulfur, contained, like the Indiana coal, a large part (40,5 per cent) of its sulfur in the organic form. Table 50 shows the forms of sulfur in the five coals examined and some other well knov/n iiiastern and Central District coals. Table 50 Pyritic and Organic aulfur in Various Coals Dame of coal Total sulfur Per cent pyri tic Sulfur Pine dissem- inated p^^’r- itic sulfur Organic sulfur per cent Per cent Per of total cent sulf ur Per cent of total sulf ur Per cent Per cent of to- tal Herrin 2.70 1.80 67.0 .92 34.0 0.80 33.0 Bon Air 4.87 3.70 76.0 1.83 37.6 1.17 24.0 clover Hun 3.46 2.77 79.6 .50 14.3 .71 20.4 V/est Virginia 2,48 1.47 59.5 .71 28.6 1.01 40.5 Indiana No, 3 3.88 2.06 33.0 1.45 47.0 1.82 47.0 Ivliddlefo rk 8.29 1.99 60,5 • 77 23.4 1.30 39.5 (Benton, 111 inoi s j No, 12 W. Kentucl; > •• • - . I • ' .1 N rH o 192 cti •H 4-> o -p ^ G 1 _ o o (u a> rocvj rH o-,(XD cv-o rH CO C\JrOC\J(X) CO d P4 o j ^ rH rH 1 — ! OO rH OJ rH i — 1 r-H rH rH ^ -d i U -C\) O'NrHOO O CO O ITN t>_ - O OMTNvO lr\ vO ITS ONCO CO 4- rH ( — 1 1 — 1 rH a -d -p COC 3 N lr\00 OlTN-;!- ONO OJ (>-CO rH ^ d d ♦ # ••• ••••• «••• • CO 0) (U V \Ov£> CO'^ON C\jMDrHe0t>~ CO OJ COC^ ITN cd •H O COCO CO ONco cjNcoo g'ncoco CO cr- cOCM (7^ cd rd P d bO P" DO (1> (U t>-I>-COrHrHCr\rH'Lr\ OO t>- ITN lT\ H ICN 0^^ r; <; ph o rH rH 1 — 1 rH •H 1 — 1 to • nJ o d +5 IfNlTN O^ONVO O O O O t>- O lr\lr\ OCOOlT\ -H p d o> -rH ro -C0 l>-C>-cocooo t>- coc^co >H 4^ rQ bO bOrQ bD4i rQ bO bOpJ bOrQ 4 ! po po pj 0 0 o ^ •H cd -H cd cd -H -H cd -H cd cd -H -H cd -H cd cd cd cd cd cd 0 0 cd i-aEH-jC-HH-adEH-jEHEHi-a -DEHt-jEHEHEHEnpiEH ■si xi xi CO CO CO d d P P P P ^ d! CU (D 000 cd cd d d d d -H -H -H ro -H s; !zi d; {dcdfdr— ccjpddPlrH cc; PPP CO ' — dcdcd d d dd-H-H-Hppp— podd dddd CO GO o •H.H > t> >ddd— cs-rH-H-'^ cd cd p ppdddooo'^ oPPPCM p'd'od 0 0 ddOOOrHrHrHO- rHP-CO <3^ 0 rH CM CO H IfNvO t>-CO 1 — 1 1 — 1 1 — 1 1 — 1 1 — 1 rH 1 — 1 ( — 1 1 — 1 '■ " • ' — — — 193 tained a large proportion of heavy clean shale. The smallest re- duction was on the Bon Air coal. This coal, as the analysis of the raw coal shows, contained a large percentage of ash, hut it was largely in the form of very thin hands of shale interhedded v/ith the coal and the disseminated ash of hone coal and light carhona- ceous shale. The effect of this is shovm in the specific gravity analysis of the raw coal. Even when crudied to one-fourth inch maxi- mum size, many particles are part dirt and part coal. Only 60 per cent floats on a solution of 1.30 specific gravity and only 4.1 per cent is heavier than 1.60. The remainder 35.9 per cent is in- termediate in deYisity, and consists of middling coal particles, high in ash. Fig. 3, in Chapter III, shows the specific gravity analysis of the Bon Air coal compared with the Herrin coal which is much more amenahle to washing. The Bon Air coal contains 36.1 per cent of material Between 1.30 and 1.45 in specific gravity, while the fraction Between these densities in the Herrin coal amounts to only 15.5 per cent of the total. Another factor which affects the result of v/ashing on the Bon Air coal is the hi^ ash content of the liglitest coal, floating on 1.30 specific gravity solution. This analyzed 10.1 per cent, v/hile the corresponding increment of the Herein coal contained 4.64 per cent, of the Indiana coal 5.4 per cent, and of the Clover Hun coal 5.8 per cent. The Bon Air coal is a typical Boney coal con- sisting ma.inly of dull coal or atritus. Bone coal and light carBons.- ceous shale. As received, the coal sample sho\ved very fev/ Bri^t coal particles. The Bon Air coal v’as the only coal of its type examined during this study. Such coals are common in the Western and t « \ X r# h ■ O ; > -i i I f ( < ( c I 194 Alaskan fields. Tables 54 and 55 show specific gravity analysis of two such coals which contain even larger percenta.ges of middling. In washing these coals, the separation between washed coal and refuse has to be made at a much hi£^er specific gravity than in the avera.ge Eastern or Central District coal and a higher ash fuel must be acceptabJ.e. TAEhS 54 Specific Gravity Analysis of a Washington Coal^ Number 2 Bed 0” - 2^-’* Size Specific Gravity Per cent of rav/ coal Per cent ash Float on 1.40 1. 40 to 1, 50 1.50 to 1.70 Sink on 1.70 Total sample Float on 1.40 1.40 to 1.50 1.50 to 1.70 Sink on 1.70 Total Sample 38.9 14. 4 16,7 100.0 Same 0” - 3/8” Screenings 56,3 8 . 1 14, 4 21.2 100.0 11.9 26. 2 39. 2 36.6 8.8 25.2 36.2 ISjJ, 27. 5 The analysis of the Washington coal shov/s it to be a mixture of clean coal, bone coal, snd shale with only a small pro- portion of free particles of clean coal in the 0” - 2^-” size, The 0” - 3/8” size shows a. much larger proportion of material lighter than 1,40, but this is not entirely due to a more complete separa- tion of dirt particles from coal particles at the finer size, as ^^^xperimental v;ork by S. R, McMillan, Northwest Station U. S. Bureau of Mines* ’ ’X*iClk X,'^ ' K ■ f ■i < :) i[ 19 5 the average ash content of the entire sample is much lower than in the O'* - 2 ^*^ unsized coal. The coal is washed at O'* - 2'^'* size on Blair jigs yield- ing 60 per cent of washed coal with an ash content of 19. 1 per cent and 40 per cent refuse carrying 59.1 per cent. T.'iBIJE 55 Specific Gravity Analysis of a Nev/ Mexico Coal Specific Gravity Per cent of sample Per cent ash Ploat ; on 1,25 0.39 4.4 1.25 to 1.30 23. 10 7.4 1.30 to 1,35 29.59 11.4 1.35 to 1.40 11. 55 16.9 1,40 to 1.45 5.15 21.3 1.45 to 1, 50 5. 19 25. 8 1. 50 to 1. 55 6.81 31.8 1. 55 to 1.60 3, 22 36. 4 1.60 to 1.65 3.77 40.1 1.55 to 1.70 2. 59 44.7 1.70 to 1.75 1.98 46. 1 1.75 to 1.80 1. 17 51.9 Sink on 1.80 5. 69 65. 5 It is worthy of note that of the five coals examined the Indiana coal,Vvhich gave the hest results in the way of ash reduc- tion, showed the lowest reduction in sulfur, and that the Clover Run coal on which the greatest reduction in sulfur was secured shov/ed a comparatively sma,ll improvement in ash content. This is contrary to the general statement sometimes made that the sulfur follows the ash. On the Indiana coal tests, the very fine v/ashed coal, designated as sludge in the reports, contained a very large per- centage of ash, 34.8 in the 0*' - test, and 32.3 in the 0“ - i*' 196 test. This indicates that the fire clay was not separated from the coal, hut due to the very fine size of the particles it was carried i over the washed coal discharge side of the table with the light coal. This happens to a greater or less degree in any coal v;ashing operation, but was most noticeable in the Indiana coal tests be- cause of the exceptionally large percentage of clay in the raw coal. This effect is explained by the theory of settling velocities, Chapter III, as due to the fact that the ratio of sizes in the feed exceeds the ratio of sizes of equal settling particles of coal and shale to such an extent that the smallest particles of the heavy mineral settle at the same rate as the largest particles of the light mineral. While it is well known tha,t a ratio of sizes great- ly exceeding this theoretical settling ratio nay be handled togethei efficiently, it is often observed^ that the very fine material in the feed to a coal washer is not cleaned. At the Middlefork washer ^vhen the coal was washed at about 0” - 1^-” size, the fine material which was not appreciably | benefited by the operation, amounted to from 8 to 10 per cent of j the raw coal fed, I Due to the disintegration of friable shale and clay par- |j ri tides in the washer the fine washed coal is sometimes higher in j I ash content than the corresponding size in the feed. This has evidently taken place in the Indiana coal tests. The fine material may be partially separated from the coarse washed coal by wet screening or by the use of a perforated bucket elevator or a de- ^Coal V/ashing, Coal Wendell, An article to be published in Coal Age; Coal Washing, * Ernst Frochaska, ! ’X \j . ' 1". ■' ^ .'-uj iXJi F A 9 * • f I ^ ^ O'*! ♦. •*rlC JjiHj* »i <=>-.* .=• o.: ’...;: :. .^ • .. i"i a.-ii . 0- i- oJ- r' ..' .-;v ..iioo ,t;i ;■;•>/ TO oj I:-?' " , - i .r.^;40* .:;00 .:n.^XO?tI 0|- •; .,! t .:O0X J O.- 1 ^ om ^ ■ X‘^XO 1- ^,1 L,.^wXJc;?>ovft 9^. ;-« A.I.lw V OL' '.icn.f-’ .» aL" V' '>--ai.>Xq3?t '>i «■ -9 . »:X ...^ .'Ji Ovi'r.cj i»; oXx.'r ttL: * ■> .t i’oal oi »i.'h , Til r ''.'-»t » r ■ ;• C.; j'-:^., X-wpo 1<5 j l<; oXiai '*- ■ ’ ■* ^ w*.- *■ r.^j ■•-r f .-tta r* «Xj-. ■;.. ’ - - '. ■; w o:/T'-q j. _ , fut: , , -.rj-iro-® XaTaJti.-;^ ^ •* •■!*. .■’f- '» ', *r •“ ^ #r «' •• ' 1 "', ■ ■ ^ . . ,.Cc.*' iv. id\ii .) I I juO* J O a .' j Ki.;.u^ T Tli;oS>OK'j» \ [ ;tx orii’i /\-;«v -^fiovror o . ai ' ,; ' uoi / ;.jnro 30t. «. T3*'ia.?v.- '^-wD jj 5o;>‘: v'*A ;j >• , I-jjp qoj'/» *'».{s.‘.vr .(10‘l*9lI)£'^I! v-'f+ .Vs \:i*f tcft ftj. - r. ;-r J r -TT-f C' o' :V ei ' ' ' ?^^^^ , irii .: - "C itfoox. r;'." . «oq'S 0 J i>» .')'9 v-.r-x 3f;,J :-3 r» . ■ ^r'r^itZ 'lo rc..;Jvi'x:v>"ni<:a'*> o-v Ct4 c«Xi.<^ ni .a-rQ'ia’ uo.:ij‘. ,•. ^>.ii ‘xs£(i»jjw tfjl. -.'Jt idiQ: .t It.', oic , . a«'iu ‘lil-rtoco®'; ': ;.n q.','« ;icrj A*''- - • snil :>fu , i.-, o.‘ ! : .'u\ s b r’.'l ‘ ■ .ij ro.^fq f{t>;4x: t . ■ V ir.p ^;y/' XR-3d A.yji-.o; •ij'isoo ii.it ,;r;>v; 0^».T ,. Tcilr., »*! • v J ^ 'X. ro..;ivaJ3 *> ji ^ i.'i 0 -i/r acf ‘lo asi/ firfj' vi 'fc ■ •, '; cJ t*Xoi^TC;3 V ♦ '■ 1 rt©7/ Xi.o'' X i . - -riooti ^o-xa:\’. ixiBxiV lm.O : .;^^ ,;x 197 watering conveyor to move the washed coal from the collecting sump to the storage hins. It is usually not high enough in ash to he discarded as refuse, hut may he cleaned by rewashing separately, or may he used separately as a secondary coal. Pistjoss-l hy the Washer of Particles of Various Spec if- ic Gravities . As already pointed out, the washahility of a coal depends very largely upon the method of occurrence of the impuri- ties. If the excess ash and sulfur are concentrated in a compara- tively few particles of high specific gravity, the coal lends it- self well to the washing process, v/hile if the impurities are dis- tributed throu^ a large proportion of lighter particles the coal is difficult to wash. Specific gravity analyses of raw coal sam- ples and samples of the resulting v/ashed coal show what kind of par- ticles go into the washed coal and hov/ much of each heavy specific gravity increment in the raw coal is removed. Table 56 gives these figures for each of the coals exarained. 9 E ! 5 . rr c :< • > ■ r-a O'-’ t f .'•J ^.r:;j,-i3 0c \ ■: '-.ictf ^ ' .V /or: ^ i J- ^ . ., > • • '• • o v*-J , * ' * l*b . ■ ' • ^ M '» : .> * • > <■> • T ■ J ,1 ' ~ ^ .•w ' ;.’■ -1 , • ’ ■> ■•' " ^ '>•■•■ « ; -,l i-' a UQ^i' ' .. -:.‘l:i/b on.' fi. . ;nf>orco « .:> tf . -?r a-tr- 3 E *' , C ' : oj>qi ,: liO.roiJ'Ifi : S'*?! -^XiV'- ..'. u : iTTi-q-j.-i i c ir 'vlir'v,; ^ ^ • .i* T \.. iv.:-;; t, ^ - ^Ui'r s • I, OJ ' . ‘t> rio..-.o *i£*l 199 These figures for v/ashed coal in each case represent the cleanest coal secured. In some of the tests this product, desig- nated ITo. 1 coal, amounted to too small a percentage of the raw coal for the production of a washed coal of that quality to he com- mercially feasible, unless a certain tonnage of secondary coal of considerably hi^er ash content can be disposed of. In the table tests almost all the material heavier than 1.80 specific gravity was removed in each case, leaving a residual portion amounting to from 0.4 to 0.5 per cent of the v/ashed coaT. Generally speaking, there v;as a small percentage of each of the heavy increments above 1.45 in specific gravity in the washed coal than in the raw coal. The percentage of middling particles lighter than 1.45 was generally no lov/er in the washed coal than in the raw coal. On the Washington coal, washed at 0^’ - 2 ^^* size v/ith the Blair Jig, the washed coal contained 3.4 per cent of naterisil heav- ier than 1.70 in specific gravity and a little smaller percentage of middling, from 1.50 to 1.70, than the raw coal. There was a \ concentration of particles lighter than 1. 50 in the clean coal. | II Since this coal is so radically different from the five coals exam- ined at Urbana, it is impossible to make any comparison in the work of the machines. The figures on the Washington coal merely illus- trate the fact that the washing of such a coal presents an entirely different problem from that of the Eastern District coals. The ob- ject aimed at is to make a separation at about 1.50 specific grav- ity and produce a low grade fuel from an otherwise valueless mate- rial. 200 Tatle 57 shows the distribution made by the washing table of the particles of various specific gravities in the rav/ coal. The figures given were secured in the 0” - 4'*' test on the Indiana coal using the coinmerical size Deis ter-0 vers trom ts.ble. An unavoidable error v;as incurred in making the specific gravity tests on the washed coal because of the loss of very fine slime in the heavy solution used. For this reason the value given for sink in 1.80 specific gravity solution is too low. 57 Specific Gravity Analyses of Products of the 0** - V/ashing Test on Indiana No. 3 Coal Wa shed coal Refuse Raw coal Per Per Per Per By Specific Gravity cent cent cent cent analysis V/'ashed coal of of plus raw rav; refuse coal coal Lighter than 1,25 79.3 68.9 — 68.0 68.9 1.25 to 1.30 3. 6 3. 1 .2 2.8 3. 1 1,30 to 1.35 5.9 5.1 .1 5.4 5. 1 1.35 to 1. 40 3.6 3. 1 .2 3.7 3. 1 1.40 to 1.45 3.0 2.6 4.2 0.5 2.8 3. 1 1.45 to 1. 50 2. 5 2. 1 2.4 0.3 1.9 2. 4 1. 50 to 1.60 1. 5 1.3 5.0 0.7 2.6 2. 0 1.60 to 1.80 0. 2 0. 2 16.0 2.0 2,3 2. 2 Heavier than 1. 80 0.4 0.4 72.0 9,3 10.5 9.7 Fig. 34 shows graphically the distribution made by the laboratory ta,ble of the various kinds of particles as regards both specific gravity a ,nd size . For this work a sample of the U'est Virginia coal at 0 - 3/8 ” size was used. The data was secured by making a specific gravity analysis on each of the four products. No. 1 coal, No. 2 coal, No. 3 coal and refuse and screening each 1 202 specific gravity fraction into three sizes: 0" - i/Q”, l/8” - and - 3/8«. ■- The area of the large square in the figure represents the entire coal sanple 100 per cent. Therefore the percentage relation of each product to tlie original raw material and to each other prod- uct is represented ty the relative areas on the graph. In addition, the cumulative yield of washed coal securahle by combining products may be read from the horizontal scale and the cumulative percent- B.ges of float in each product may be read from the vertical scale. shov/s This graph in the upper right hand corner) that the loss of good coal, float on 1.25, 1.30, and 1.35 specific gravity solu- tions consists almost entirely of large particles, while the heavy particles in the No. 1 washed coal are all smaller than one-ei^th inch, as shown in the lov;er left hand corner. This is due to fine clay particles carried over with the washed coal near the head mo- tion end of the table in the section marked No. 1 in the drawing Fig. 24. 1 * In all the tests in v/hich a natural feed was treated cn | ! the tables and the special equipment for dividing the product into | i a number of separate parts was used, a. highier ash content wr.s se- | \ cured in the sample discharged into this No. 1 section than in sev- eral sections following. This was especially marked in the test on | 3 \ the Indiana coal where the product from section No. 1 amounting to | 11.6 per cent of the feed carried 10.2 per cent .ash, while the ma- terial going over between this section and a point about half v/ay to the middling corner carried only from 5 to 6 per cent. ^Containing all sizes from a given mo.xiirium down to 0. 203 36, Efficiencies . The formula devised for calculating efficiencies, I Actual yield x actual ash reduction Efficiency — Stan da I'd yield-^ x standard ash reduction was applied in all the tests made and was found fairly satisfactory. For comparing the results secured with different machines on the same coal, the efficiency figures give an indication of the rela- tive advantage of the machines used for treating that particular coal, hut when the operations to he compared are on radically dif- ferent coals, the comparison of the machines hy the efficiency figures is uncertain, because the completeness of the separation secured depends upon the nature of the coal as v/ell as upon the process used. The efficiency, as calculated, depends upon the pro- portion of heavy material taken out as a percentage of the total amount of heavy material occurring in the raw coal. The figures of Table 57 indicate that the average percentage of sink particles retained in the washed coal is a more or less constant minimum rather than a certain proportion of the amount occurring in the | 5 k original raw coal. For this reason a coal like the Indiana No. 3, » which contains a large proportion of heavy removable refuse will j sliov/ a higher efficiency, as calculated, than such a coal as the | I V/est Virginia sample which contained only a very small percentage of sink particles. This may also explain the hi{^ efficiency of the jig operating on the Washington coal which shows, by calculation ^Yield by sink and float test on the solution used as the permissible bath. •• i > -i. L» .i ' ' i ; I-.' >■ >j,; V V j £.1.' • ■ 'j C :\SZf‘i-V t '' ■' / Oi i . .. . . . < Zl X. . •. . ..I’ .... *‘~4 #fcjQflk rj:.-:; '.,j n*. 'j ' ii 1 j" f ^ ^ ;.. U • .r. r I ■^-. 90 svi:^ : .i-::i n . v:.'Aoiuxn« ■:n._ b'.-ns ---snu ;" 'r/ r ; •'• • ■ • '• ■ ji. ' -iO VV ‘ ' ‘ n^oii *rf: , ,,.-j ■ r.* :^. ■ ^ --^-v , i T? '• f. ; X«;oc '.o . :r?nx . 1-"- , * . •>-':. r ' . * ‘ .1 . _ i" ■ ?« ii-l l^V ■ -■' . .' .•- '■■ . n".*? . 561 V “ f \ - 1 V .’' . . fjii. '.'w *irv ! T'J 'ji. 'S< * ^ ■I- -i- l A » ,r • X ; ^<.'6 1 - ■; 'ii . '•m'Qi.'X Jf r.” ■f ' I r'.-.'.i .' rr: . ' i'C N 1*^ •V « riw:‘ .O’. iijL/U *I« , .*'..;.'5: t-\- ' •*■"* k '-■ fi’. A' * !>• 1 x.^’^r tv -A on 204 from the above formula, an efficiency of 97 per cent while the washed coal contains 3.4 per cent of the heaviest material as com- pared with 0.4 to 0.5 per cent for all the other coals reported. Table 58 shows the efficiencies secured in the tests. t;\ele 58 Efficiency Figures For the Washing Tests Per cent ash_. _ .. . Yield Coal Size Machine Raw Washed Float Float Washed Effi- used used coal coal coal coal coal ciency Herrin ^ 1 , 1” JiS 11.0 7.7 5.6 82. 0 89, 5 67 Herrin - ^11 Table 14.2 7,2 5.4 82.0 78. 5 76 Eon Air 0" - 3/S” Jig 15, 1 13. 1 12. 1 92.0 SC, 6 56 Bon Air Q» - 3/8** Table 15. 1 13.3 12. 1 92.0 86,6 56 Clover Run Clover o» - 1'* Jig 12.8 9.8 5.4 74. 5 78,0 44 Run Clover ^1! — 1'* Jig 14,1 11.4 6.2 65.0 85,0 48 Run O’* - ^11 Table 10.4 6,2 4.8 85, 1 82. 5 74 Clover Run West 0" - 3/a "Table 12,8 7.9 74.7 80 Virginia West g« — f « Jig 6.8 5.3 4.0 91.2 84,0 48 Virginia West — Jig 6.9 5. 5 4,0 90.0 83. 5 45 Virginia o« 3/8*» Table 6.8 4.8 3.8 93,3 74, 5 54 Indiana No. 3 0” Table 18,7 9.0 83.8 85 Indiana No. 3 O'* - Table 16. 5 8. 5 87, 1 86 Considering each coal separately, washing on the table at fine size showed, as a rule, a sli^tly higher efficiency than jigging at larger size. The low efficiencies secured in the jigging tests may be due, in a measure, to the difficulty in adjusting the operation properly in short tests of this kind. It is very probabl.e that un- 205 der continuous operation the specific gravity separation can he more nearly duplicated. The operation of the table can be brought to the correct adjustment much more quickly because the material being treated is spread out on the table deck in full view of the operator and every stage of the separation being made is under ob- servation; while for the adjustment of a jig the operator must de- pend entirely upon an examination of the products after they are discharged from the machine. This is a condition v/hich even in con- tinuous operation militates against the efficiency of the jig. The fact that coal of jigging size usually contains more middling particles than the sane foal crushed to finer size for table treatment also makes it more difficult to make a close spe- cific gravity separation v^rith the jig. This was especially true in regard to the tests on Clover Bun coal and accounts in a large measure for the low efficiencies on the jig tests with this coal. The preliminary sink and float tests showed conclusively that in the larger sizes an efficient separation at 1.35 specific gravity, the solution which gave the desired quality of float coal, could not be made without a very large loss in the refuse, resulting in a prohibitively low yield of washed coal. These tests indicate that tabling at fine size will pro- duce a cleaner washed coal than jigging at larger sizes. This ap- plies especially where the problem is to remove the sulfur from a coal in which it occurs as thin fla.kes and veinlets of pyrite. In the tests on the Clover Run coal which was of this type, the wash- ing table, treating a feed of 0" - 3/8“ size, produced a washed coal of 1,53 per cent sulfur, while the jigging test on 0“ - 1” feed gave a smaller yield of washed coal analyzing 2.02 per cent 206 sulfur. On the West Virginia coal, which contained 70 per cent of its sulfur in the organic and fine disseminated pyritic forms, a small No. 1 coal product was separated out vdaich analyzed 1,6 5 per cent sulfur and was sufficiently clean for tt-ie purpose desired, al- though of too fine size. This greater effectiveness of the table over the jig in reducing the sulfur content is due more to the fact that fine crushing frees the pyrite particles from the coal parti- cles than to a more perfect separation between particles by the table; althou^, as the efficiency figures indicate, the latter con- dition is probably true in s measure. In preparing coal for coking, where the fine size of the washed coal is no disadvantage, the table may, therefore, be used to advantage. In preparing coal for fuel the advantage of more ef- fective cleaning is probably more than offset by the disadvantage of fine size, unless fine coal is required for some special use.