ILLINOIS STATE GEOLOGICAL SURVEY 3 3051 00005 6410 STATE OF ILLINOIS DEPARTMENT OF REGISTRATION AND EDUCATION DIVISION OF THE STATE GEOLOGICAL SURVEY M. M. LEIGHTON, Chief REPORT OF INVESTIGATIONS — NO. 34 CONTRIBUTIONS TO THE STUDY OF COAL Banded Ingredients of No. 6 Coal and Their Heating Values as Related to Washability Characteristics AND Preliminary Report on Unit Coal-Specific Gravity Curves of Illinois Coals BY L. C. MCCABE, D. R. MITCHELL, AND G. H. CADY PRINTED BY AUTHORITY OF THE STATE OF ILLINOIS URBANA, ILLINOIS 1934 STATE OP ILLINOIS Hon. Henry Horner, Governor DEPARTMENT OF REGISTRATION AND EDUCATION Hon. John J. Hallihan, Director Springfield BOARD OF NATURAL RESOURCES AND CONSERVATION Hon. John J. Hallihan, Chairman Edson S. Bastin, Ph.D., Geology William A. Noyes, Ph.D., LL.D., Chem.D., D.Sc, Chemistry John W. Alvord, C.E., Engineering William Trelease, D.Sc, LL.D., Bi- ology Henry C. Cowles, Ph.D., D.Sc, Foi estry Arthur Cutts Willard, D. Engr., LL.D., President of the University of Illinois STATE GEOLOGICAL SURVEY DIVISION Vrbana M. M. Leighton, Ph.D., Chief Geological Resource Section Coal Division Oil and Gas Division Non-Fuels Division Areal and Engineering Geology Divi- sion Subsurface Geology Division Division of Stratigraphy and Pale- ontology Division of Petrography Division of Physics Geochemical Section Fuels Division Non-Fuels Division Analytical Division Mineral Economics Section Topographic Mapping Section (In cooperation with the United States Geological Survey) Publications and Records (36878) Contents PAGE BANDED INGREDIENTS OF NO. 6 COAL AND THEIR HEATING VALUES AS RELATED TO WASHABILITY CHARACTERISTICS 7 PRELIMINARY REPORT ON UNIT COAL-SPECIFIC GRAVITY CURVES OF ILLINOIS COALS 45 Digitized by the Internet Archive in 2012 with funding from University of Illinois Urbana-Champaign http://archive.org/details/contributionstos55733ball BANDED INGREDIENTS OF NO. 6 COAL AND THEIR HEATING VALUES AS BELATED TO WASHABILITY CHARACTERISTICS Outline Page Introduction 7 Purpose of investigation 7 Scope of investigation 7 Comparison with previous investigations 9 Acknowledgements 11 Procedure 11 Channel sampling 11 Laboratory preparation of channel sample 12 Physical character of the banded ingredients 14 Megascopic character and distribution of the banded ingredients 14 Microscopic nature of the fractions in thin and polished sections IS Analysis of the banded ingredients 23 Sampling of bands 23 Analytical results 30 Discussion of test results . , 33 Washability curves 33 Heat- value curves 33 Regional variation 35 Southwestern Illinois group . 37 Southern Illinois group 40 Specific gravity 42 Summary and conclusions 42 2 Tables Page 1. Location of mines, by county 9 Percentage of banded ingredients 14 3. Specific-gravity distribution of banded ingredients in sample from Mine J 16 4. Analyses of banded ingredients 26 5. Fuel ratios of banded ingredients 31 6 Unit coal calorific values of face samples and of samples of banded ingredients 32 7. Comparison of coals at 5 per cent recovery intervals 34 8. Tabulation of float-and-sink data 36 Figures Page 1. Map showing locations of the mines sampled 8 2. Cutting a column of No. 6 coal 10 3. Typical block of No. G coal showing two varieties of banded ingredients 12 4. Block of No. 6 coal showing vitrain and durain 13 5. Block of coal composed of partly mineralized fusain 15 6A. Fragments of coal of low specific gravity 17 6B. Mineral matter in fractions of high specific gravity 19 7A. Thin sections from float-and sink fractions 21 7B. Polished surfaces of fragments of high specific gravity 22 7C. Polished surfaces of fragments of high specific gravity 24 7D. Polished surfaces of fragments of high specific gravity 25 8. Washability curves of Mines A, B, and C 38 9. Washability curves of Mines D, E, and F 39 10. Washability curves of Mine G . . . 40 11. Washability curves of Mines H, I, and J 41 BANDED INGREDIENTS OF NO. 6 COAL AND THEIR HEATING VALUES AS RELATED TO WASHABILITY CHARACTERISTICS By L. C. McCabe, 1 D. R. Mitchell, 2 and G. H. Cady 3 INTRODUCTION Purpose oe the Investigation A comprehensive investigation of the nature of Illinois coal, antici- pating the application of the knowledge obtained to the preparation and utilization of the coal, was initiated in 1931 as part of the program of mineral research by the State Geological Survey. The coal investigation was started with the systematic examination of column samples of Herrin (No. 6) coal in southwestern and southern Illinois. Such examinations by this and other laboratories have directed attention to the importance of recognizing the fundamental differences in the banded ingredients of bituminous coals such as are mined in Illinois. The present bulletin describes an investigation of the redistribution of the banded ingredients in the fractions obtained by standard float-and- sink methods and the effect of such redistribution upon the ash content and heat value of the separated product. The results obtained suggest certain implications with respect to the combustion characteristics of the prepared coal. The investigation, as carried on, made possible the deter- mination of ( 1 ) the usual float-and-sink data for the coals investigated, (2) the extent of the separation and /or concentration of the banded ingredients in the various fractions, and (3) the possible effect of the redistribution of the banded ingredients upon the ash content and heat value of the fractions. Scope of the Investigation The investigation employed samples of Herrin (No. 6) coal from 10 mines (Table 1 and Tig. 1) in southwestern and southern Illinois, the samples representing the general variations in the seam in the south- ern part of the State. 1 Assistant Geologist, Coal Division, Illinois State Geological Survey, Urbana. 2 Assistant Professor, Mining and Metallurgical Engineering, "University of Illinois, Urbana. 3 Senior Geologist and Plead of , Coal Division, Illinois State Geological Survey, Urbana. [7 ] C0NTBIB1 TIONS TO THE S'l 1 HI OF COAL Fig. 1. Map of Illinois showing locations of the mines sampled. BANDED INGREDIENTS OF NO. 6 COAL 9 Table 1. — Location of mines by county Mine A St. Clair Mine F Randolph Mine B St. Clair Mine G Perry Mine C St. Clair Mine H Franklin Mine D Montgomery Mine I Franklin Mine E Washington Mine J Williamson The sampling, experimental tests and laboratory procedure were as follows : (1) Initial channel and columnar sampling (2) Standard float-and-sink separation (3) Chemical analysis of fractions (4) Megascopic and microscopic determination of the banded in- gredients and mineral matter (5) Compilation and interpretation of data Comparison "With Previous Investigations Numerous float-and-sink tests have previously been made on Illinois coals ; 4 the present tests supplement but do not duplicate earlier informa- tion. The cleaning possibilities of the coals studied in the present in- vestigations are shown by the standard washability curves, but these data are supplemented by an additional series of curves, not accompanying previous reports, which indicate the effect of cleaning on heating values. The determination of the distribution of heat values among the different fractions and the graphical delineation of the information are important additions to conventional float-and-sink data. The latter pro- vide a control on the ash content of the product of a cleaning operation and the additional data make possible greater uniformity of quality. The value of the calorific data would undoubtedly be greater if, as may eventually happen, an improvement in heat cjuality would insure a premium price on a coal, for in this case larger losses from cleaning could be endured. But even under present conditions where the producer is primarily interested in selling a certain quantity of coal and the con- sumer in buying a certain quantity of heat, it may be of sales advantage to be able to produce a coal of higher calorific value if only a slight ton- nage loss is sustained thereby. 4 Coal washing in Illinois: Univ. of Illinois Eng'. Exp. Sta. Bull. 69, 1913. Dry preparation of bituminous coal at Illinois mines : Univ. of Illinois. Eng. Exp. Sta. Bull. 88, 1916. Cleaning tests of central Illinois coals : U. S. Bureau of Mines, Tech. Paper 361, 1925. Coal washing investigations, methods, and tests: U. S. Bureau of Mines Bull. 300, 1929. Washability tests of Illinois coal : Univ. of Illinois Eng. Exp. Sta. Bull. 217, 1930. The possible production of low ash and low sulfur coal in Illinois : Univ. of Illinois Eng. Exp. Sta. Bull. 258, 1933. Ill ( (in mini tions to THE STUDY ok ro.\l. Thus it is possible to reduce the ash of one of these coals from 14.28 per ccmI to 8 per cenl by cleaning al a poinl which will give 91 peT cent tonnage recovery. Al the same time 98.5 per cenl of the B.t.u. would Fig. 2. Cutting a column of No. 6 coal. The face sample was composed of cuttings from the channel to the right of the column. be recovered and the B.t.u. value of the clean coal would be 12,485 as compared with 11,615 for the uncleaned coal. The consumer would not only buy less ash and sulfur but would receive 7.5 per cent more heat BANDED INGREDIENTS OF NO. 6 COAL 11 than is present in an equal tonnage of untreated coal. It is quite reason- able to believe, furthermore, that coal at, let us say, 12,600 B.t.u., might sell at a premium above the price received for coal of less heat value. In such a case it would be important for the producer to know the loss that would be entailed in increasing the heat value of his coal to the higher specification. An additional distinctive feature of this investigation, with respect to Illinois coals at least, is the determination of the extent of separation and concentration of the banded ingredients (vitrain, clarain and fusain) effected by the float-and-sink process. To accomplish this, samples of each fraction were studied as they came from the separating liquid, using an ore-dressing microscope. In the course of a parallel investigation, the proportions of ingredi- ents in the column samples of these coals had been carefully determined. With this information at hand a rough check on the values obtained in the study of the float-and-sink fractions was possible. Acknowledgments The greater part of the experimental data were gathered by the senior author as a graduate student in the Mining Engineering Labora- tory of the University of Illinois. The associate authors were active in directing the work and in preparing the report. The release of the laboratory data for publication by the Dean of the College of Engineering and the Head of the Department of Mining and Metallurgical Engineer- ing is gratefully acknowledged. The writers take pleasure likewise in acknowledging the coopera- tion of the management of the mines where samples were collected and of Dr. 0. W. Bees, Analytical Division of the State Geological Survey, and his assistants for chemical analyses. PBOCEDITBE Channel Sampling A face sample from each mine provided the material Cor the tests. This consisted of the coal cut down along one channel adjacent to a column sample (Pig. 2) and supplied 10 to 15 pounds of coal for each foot of the seam. An effort was made to duplicate as nearly as possible the tipple feed involved in the cleaning process. In nine of the ten mines therefore, no impurities were excluded from the face samples be- cause in these mines cutting machines are operated in the bottom of the ccal and the entire fall of coal is loaded, the larger sizes being hand picked at the tipple. In the mine in Washington County the character- 12 CONTRIBUTIONS TO THE STUD1 OF COAL istic clay "blue band", normally 1 ' '■_> to 3 inches thick, thickens to 8 inches. Cutting machines are operated in this band, removing the greater pari of it, and any < • I .- 1 \ left adhering to the coal is removed during Loading. The "bine band" was therefore excluded from the sam- ple taken in this mine. Fig. 3. A typical block of No. 6 coal, natural size, showing two varietes of banded ingredients, vitrain (V) and clarain (C). Laboratory Preparation" of Channel Sample Each sample when cut down was sealed in a large can in the mine and transported to the laboratory where it was pulverized to minus ^ inch. From this a sample of about 2 pounds was then cut out with a BANDED INGREDIENTS OF NO. 6 COAL 13 riffle and a sample varying from 6 to 10 pounds was taken for the float- and-sink procedure as described by Callen and Mitchell. 5 The material passing a 48-mesh Tyler standard screen was excluded from the head sample used in the washability tests as this fine material remains in suspension for some time and contaminates the solutions used in the specific gravity separations. The material remaining on the 48- mesh screen was air-dried for 24 hours before the float-and-sink tests were made. Fig. 4. A block of No. 6 coal, three-fourths natural size, showing a band of vitrain (V) between two wider bands of splint coal (durain, D). Mixtures of benzene and carbon tetrachloride were used in pre- paring the series of liquids with specific gravities of 1.30 to 1.50 and mixtures of carbon tetrachloride and bromoform were used in preparing the heavier end of the series up to 2.0 specific gravity. Separations were made on the ten samples at the following specific gravities: 1.30, 1.35, 1.40, 1.50, 1.70, and 2.0. After gravity separation the fractions were dried in the air before an electric fan for a period of 24 to 48 hours. 5 Callen, Alfred C, and Mitchell, David R., Washabilitv tests of Illinois coals: Univ. of Illinois Eng\ Exp. Station Bull. 217, p. 32, 193U. 14 ro.vntii'.i nows to Tin; si i nv OF coal A 10- to 20-gram sample was riffled from each fraction for micro- scopic study. 'The remainder of the fraction was used in chemica] analysis. Moisture, ash. and total sulfur determinations were made on each fraction. B.t.u. determinations, which are seldom included in float- and-sink work, were made on all fractions except the 2.0 specific gravity float and the 2.0 specific gravity sink. The latter determinations fur- nished the data for the construction of the B.t.u. curves. PHYSICAL CHAEACTEE OF THE BANDED INGEEDIKXTS Megascopic Character and Distribution of the Banded Ingredients These coals are of the normal banded bituminous type. In the terminology of Stopes 6 the brilliant jet-black coal is vitrain, the glossy finely laminated coal is clarain, the dull laminated grayish coal, commonly known as splint, is durain. Fusain is the mineral charcoal (Figs. 3. 4, and 5). Table 2. — Percentages of banded ingredients Banded coal ingredients Banded impurities Mine County Vitrain Clarain Durain Fusain Pyrite Bone Clay A St. Clair 13.16 76.51 3.38 5.12 1.83 B St. Clair 7.83 83.09 2.62 4.76 1.70 C St. Clair 9.95 77.58 7.43 1.82 1 . 33 1.89 D Montgomery. . . 19.5 62.1 14.9 .8 1.5 1.2 E Washington .... 13.40 68.70 15.0 2.9 (a) F Randolph Perry 14.76 75.88 4.77 4.59 G 19.00 69.90 4.50 2.6 4.00 H 18.81 77.68 1.50 .42 .61 .98 I 22.70 72.40 2.3 .10 1.60 .9 J Williamson .... 20.1 76.55 1.35 2.0 (a) Eight-inch clay band removed in mining. The values obtained in the measurements of the banded ingre- dients made on polished surfaces of the columnar sections of the seam (Table 2) are, as previously stated, an indication of the proportion in which the ingredients should occur in the channel sample used in the float-and-sink tests. Stopes, Marie C, "The Studies on the Composition of Coal," The four visible ingredients in banded bituminous coal : Proc. Roy. Soc, London, Vol. 90B, p. 470, 1919. BANDED INGREDIENTS OF NO. 6 COAL 15 Clarain and vitrain are essentially complementary in occurrence, clarain comprising the greater part of the coal. The clarain average for the mines studied was 74.03 per cent, the values ranging from 62.1 to 83.0 per cent of the seam. A coal with a high percentage of clarain is Fig. 5. Block of coal composed partly of mineralized fusain. usually relatively low in its content of vitrain, and, conversely, much vitrain indicates less clarain. The vitrain content of the coal from Mont- gomery, Perry, Franklin, and Williamson counties is relatively high. Mine J, in Franklin County, showed a maximum for the group of 22.7 per cent vitrain, mine B, in St. Clair County, a minimum of 7.8 per cent. 16 CONTEIBl TIONS TO PHE STUDY OF COM. coals, although mine I) in jMonl- Durain is an uncommon ingredienl in [llinois locally bands 2 inches thick have been observed, gomery County and in mine E in Washington County durain comprises 14.9 and 15.0 per cent of the seam respectively. The quantity of fusain in the coals studied varies from a maximum of 7.4 per cent in St. Clair County (Mine C) to a minimum of 1.3 per cent in Williamson County (Mine J) the average being 3.0 per cent. But the amount of fusain does not indicate its importance in the prep- aration and utilization of the coal. Fusain is porous and friable, readily breaking away from the coal. It is the chief source of the dust in coals; therefore, any problem of dedusting is concerned principally with its removal. Mineral matter in the form of ealcite, pyrite, and kaolinite is often associated with fusain because of its porosity. Turning to the channel samples we find that the effect of float-and- sink procedure is to bring about a selective concentration of vitrain and clarain and of the mineral matter in different fractions, the fusain being largely removed in the dust. Table 3. — Specific gravity distribution of banded ingredients in sample from Mine J (Per cent by volume) Specific gravity Vitrain Clarain Fusain Mineral matter 1.30 float. . . 10.7 6.1 2.2 .8 .3 .2 '.2 4.3 20.1 34.3 12.2 2.1 1.0 .9 trace trace trace .1 .1 .1 .1 .0 1.35 float .0 1.40 float .0 1 . 50 float . . .2 1.70 float .3 2.00 float 1.5 2.00 sink 2.2 Total 20.5 74.9 .4 4.2 The ingredients in the gravity fractions from mine J in Williamson County as determined by microscopic identification of fragments, were so distributed that the 1.3 specific gravity fraction contained 52.2 per EXPLANATION OF FIG. 6A Fig. 6A. Fragments of coal of low specific gravity and low ash and sulfur content, separated by float-and-sink methods. (X 3) a. Vitrain, coal floating in a liquid of 1.30 specific gravity. Note the comparatively small size of particles in this fraction. B, c, d. Fractions composed predominantly of large angular pieces of clarain. BANDED INGREDIENTS OF NO. 6 COAL 17 — *—_ J : " .•"■'..- - hW ''■ S "V' .ST f k-. ■ v^f^lttMl^i fiua - i ^n>4 FTP*- *•* ■',-■ *yrr ■ EBP fell ' -*r -SjT *," ^'^ HI jr&at&t^ ■ , a. sp. gr. 1.30 float fr. sp. gr. 1.35 float c. sp. gr. 1.40 float d. sp. gr. 1.50 float Fig. 6 A. (Explanation on p. 16.) IX C0NTMB1 no\s TO THE ST1 D1 OF kiai, ccnl of the total vitrain in the sample, 71.3 per cenl of the fraction being vitrain. The fractions L.35 Id L.70 inclusive contained 91.1 per ccnl of the clarain. Fusain, as stated, was largely removed in the minus L-8 mesh "dust" and was nol carried through the float-and-sink process. However, occa- sionaJ aeedlelike strands of the anmineralized or "soft" variety of fusain are presenl in the fractions of 1.30, L.35, and L40 specific gravity. The "hard" variety of fusain, which commonly occurs as bundles of min- eralized strands, is more noticeable in the fractions heavier than L.40 specific gravity. The mineral matter is concentrated in the three heaviest fractions (1.70 float. 2.0 float, and 2.0 sink). The distribution of the banded ingredients in the various fractions of coal from Mine J is shown in the accompanying illustrations (Figs. 6A and B). The vitreous, brilliant, homogeneous appearance, and con- choids! fracture of the vitrain in the 1.30 specific gravity fraction (Fig. 6A-a) is in distinct contrast with the angular, more earthy, dull appear- ance of the high-ash coal in the 1.70 and 2.0 specific gravity fractions (Fig. 6B-e, f, g). The 2.0 specific gravity sink fraction is largely cal- cite or kaolinite plates, pyrite, clay, or shale. The bright, angular, laminated coal of the 1.35, 1.40 and 1.50 specific gravity fractions (Fig. 6A-b, c, d) consists largely of clarain. Microscopic Nature of Fractions in Thin and Polished Sections Microscopic verification of megascopic determinations, using thin sections and polished surfaces of individual fragments, readily demon- strated that the rougher identification was sufficiently accurate for all practical purposes. The illustrations (Fig. 7 A thin sections, and 7B, C. D. polished fragments) indicate the microscopic appearance of the general type of material found in the different fractions but they do not begin to embrace the range of specific variation. Vitrain such as composes a large part of the 1.30 fractions is readily identified megascopically (Fig. 6A-a). Frequently when ob- served in thin section it is highly resinous (Fig. 7A-a) or may display EXPLANATION OF FIG. 6B Fig. 6B. Mineral matter concentrated in fractions of high specific gravity. (X 3) e, f. Mineral matter in these fractions occurs finely disseminated through the coal or as fine plates. g. Fraction consists largely of calcite or kaolinite plates (K), pyrite (P), "slate" or shale (S). BANDED INGREDIENTS OF NO. 6 COAL 19 e. sp. gr. 1.70 float /. sp. gr. 2.00 float g. sp. gr. 2.00 sink Fig. 6B. (Explanation on p. 18.) 20 CONTRIBUTIONS TO THE STUD? OF COAL cellular plani structure (Fig. 7A-b). These illustrations are representa- tive of the microscopic appearance of the vitrain bands, which are known in have had their origin in the wood or bark of plants. The coal found in fractions of 1.35, 1.40, and 1.50 specific gravity consists lar»vh of cla rai n, which even megascopically lacks homogeneity. 'The photographs (Figs. 7A, c, d) illustrate this lack of homogeneity, but by no means indicate its extent. Typical low-ash chimin (Fig. 7A-c), cut approximately across the bedding, contains a predominance of fine laminae of micro-vitrain, representing shreds of woody material. Deposited among the accumulation are the spores and pollen of the flora — these appear as white, lenticular bodies in the figure. Along with the vegetable debris is a slight amount of ash-forming material. The black areas and strips in the illustration are either pyrite or fusain, both of which are opaque in thin section. EXPLANATION OF FIG. 7A Fig. 7A. Thin-sections from float-and-sink fractions shown in figure 6A. a Vitrain showing elliptical shaped resin bodies containing num- erous vacuoles. In thin section this coal in translucent; the groundmass is usually orange-red in transmitted light and the resin bodies appear wine-red. b Vitrain showing well developed cellular plant structure. Such structure is not uncommon in vitrain but is usually less con- spicuous, as in upper and lower portion of figure. The cell bodies are filled with material of unknown character and origin. That part of the vitrain composed of closely com- pacted cell wall material is orange-red in transmitted light and the material filling the cells is light yellow. c Typical translucent clarain (attritus), cut across the bedding, consisting of thin laminae of microvitrain and small lenti- cular white pollen or spore bodies. The micro-vitrain has an orange-red color in transmitted light and the spores are light yellow. (I Fusain in clarain (attritus) is frequent. The hazy white areas are open or mineral-filled cells in the fusain which is opaque and hence appears black. About a third of the material shown consists of clarain or translucent attritus. The section is cut approximately parallel to the bedding. e Mineralized fusain, the mineral matter filling the cell cavities. Sections of fusain are only slightly translucent in thin sec- tions and are frequently completely opaque or black. /. Translucent clarain (attritus) which contains considerable dis- seminated pyrite. The section is approximately parallel to the bedding. BANDED INGREDIENTS OF NO. 6 COAL 21 ■W:^ %* a. sp.gr. 1.30 float (X 100) b. sp.gr. 1.30 float (X 100) c. sp.gr. 1.35 float (X 50) d. sp.gr. 1.40 float (X 50) e. sp.gr. 1.50 float (X25) /. sp.gr. 1.50 float (X50) Fig. 7A. (Explanation on p. 20.) 22 CONTRIBUTIONS TO THE STUDY OF COM g. sp.gr. 1.70 float (X 25) Ji. sp.gr. 2.00 float (X 25) Fig. 7B. Polished surfaces of fragments of coal and mineral matter from float-and-sink fractions of high specific gravity. g Vitrain (V) embedded in a groundmass of "bone" coal (B). h Bands of vitrain (V) separated by "bone" coal (B). BANDED INGREDIENTS OF NO. 6 COAL 23 Fusain may occur as opaque masses embedded in the translucent clarain (Fig. 7A-d). A single fragment of fusain. when viewed at low magnification in the microscope (Fig. 7A-e), appears opaque except where the preparation has broken through mineral-filled cell cavities. It is through such cell openings that mineral-bearing solutions at some time found easy passage and place for deposition, resulting in coal frag- ments of high specific gravity and ash content. Clarain may contain pyrite in disseminated form (Fig. 7A-f) which in thin section appears as small black areas, thereby considerably increasing its specific gravity. When much mineral matter is present in coal it is very apparent on polished surfaces whether the coal and the mineral matter are in- timately mingled as in bone coal (Figs. 7B-g and 7C-i) or interlam- inated (Fig. 7B-h) or whether the minerals occur in relatively pure masses of pyrite (Figs. 7C-j and 7D-k) or of kaolinite (Fig. 7D-1). Other occurrences than those pictured are common, but the illustra- tions serve to indicate the microscopic appearance and general type of material found in the fractions of high specific gravity. ANALYSIS OF THE BANDED INGREDIENTS Sampling of Bands The banded ingredients from three mines in coal No. 6, only one of which, however, is among the group included in the float-and-sink studies, have been analyzed in connection with this investigation. The ingredients were picked from the coal at the face, placed in cans, and sealed in the mine. The poor lighting usually made accurate selection of vitrain a slow process, so that to save time a small sample of care- fully cleaned vitrain was powdered in a mortar, sealed in a small vial and inserted in the larger and less carefully cleaned sample. On reach- ing the laboratory the small sample was used for mine moisture de- termination and the larger sample was carefully hand cleaned for more complete analysis. All material in the fusain sample not passing a 20-mesh Tyler standard screen was discarded. This eliminated pyrite nodules and the larger mineralized particles from the samples submitted for analysis. With reasonable care in sampling to exclude vitrain bands and adhering fusain, clarain was easily collected in quantity because of its relative abundance. Durain is of such small importance that no samples were collected for analysis. J I CONTRIBUTIONS TO THE STUDY OK COAL i. sp.gr. 2.00 float (X 25) j. sp.gr. 2.00 sink (X 25) Fig. 7C. Polished surfaces of fragments of coal and mineral matter from float-and-sink fractions of high specific gravity. i Small resin bodies (R) within a groundmass of "bone" coal, the entire fragment embedded in plaster of Paris (PI). j Pyrite (P) and kaolinite or calcite (K) associated with vitrain (V), the entire fragment embedded in plaster of Paris (PI). BANDED INGREDIENTS OF NO. 6 COAL 25 Jc. sp.gr. 2.00 sink (X 25) '" 4 ' • 1. sp.gr. 2.00 sink (X 25) Fig. 7D Polished surfaces of fragments of coal and mineral matter from float-and-sink fractions of high specific gravity. k Fragment composed almost completely of mineral matter — cal- cite or kaolinite (K), pyrite (P), vitrain (V), embedded in plaster of Paris (PI). I Small needlelike fragment of vitrain (V) partly surrounded by kaolinite (K), embedded in plaster of Paris (PI). A fusain rodlet (F) is also shown. LM, < << N I 111 II I TIONS TO ITII': STI 1)V OK COAI. s ""3 . B -*- §£ co io co -r K5 lit ~ / CI O CI CO f ■*' -t- -t* 12,204 13.S37 14.170 CI C". c -f / CI CI CD — - CI 1" -r c c ■ o /- o — CO -r -v CD -f -* 1 - — 1 - V. 1 - CO it CI -T c i to -t' -r "5 CO "3 o H CD lO CS cs ci ci ■-i 01 01 -h COCO oi ci co CO CD I- CI CI CI 00 •— CI C 1 CO CO 'O CI CO CD O CI CO -f -+' O rt faJO aon co co co i — r— 1 ^H o coco CI CI CI NOW Cl IO CD CI CI CI V 'u "O co -* LO o o HCCO IO »o CO I- i-l C. CO 'O 'O "3 Sa 3 CO CI (M o O -t 1 CI 1- CO -p -f'OiO c-. o o Cl -T IR oo o co O -f 1- -r -v -v .2 fcl C3 OJ > s l~ -t r-H 00 ■* to CO -* -* o ci co O iO CD CO ■* ■* l~ i-H 00 ci >-OiO CO -f -P O io T-i IO -1- -t f H|. "O O CI -V 'O o IO t-- • CO U0 CO IO c-i ci iO o -V LO 02 O 1 3 oo ■ ■ GO • o CI oo G5 CO • OS ■ Con- dition >-( o co rf< hnm-* ihnco^ HC-im-f himoo<* +3 CD M bO 3 > u > '5 t- "5 > - 00 CM CO l> CO CO i— 1 —1 CO 6 6 6 6 6 c 3 O a a. c c Ea ) a c c b J a % c c & (7 B 3 C C c 'b _C !i a r w a i 3 p bO 3 "3 BANDED INGREDIENTS OF NO. 6 COAL 27 CO 05 O O CO O CO LO CM "O CO CM 00 lO "0 i— 1 tOHC m a CO' t- O i- co co co CO CO CO CO O'O'*-* LOiOON OLOr- O HONOO O CO 00 CO COOCOO CO CO » co co lo co co o •* cm th co co co ■<+< onion oraon oooci cotoon -^ co i> O C3 CM 00 CO CNOO"-^*'* CNfeOTH-"^" CM" CO - *-* ■hn'^"^" o'cm"-*-* Co"0~Co"co~ 0>h"m">* OSi-h^+US" "" T-H T— 1 TH 1— rH i — r- co oo o o -* r- CO N o O iO c rH O CO 00 CM CM CO rH O ■ t~- ^ "Cf CM LO 1> N CO CN HCOCC 00 rH CO CDNCC rH T)i N t>MC) co'-^Tt co co cv co co ^t TH tH 10 CM CO CO ■ . rH rr ^ NCCH CM O "" LO [^ 1^ . CO LO^C CO CM r- COOr LO rH r- LO lo oo co co t^ CDHC • o cm lo a r- o o- -HIOCC CO ^ "-0 co r~ co CM CM Cv i-i CM O ■ 1-1 cm' cm' o rH CM O • O t- tr. ■* CO CV ■ 00 O C CO rH t-^ ■*COC CO CO CO CO 1 — ■* m co CM CO ^ . COr-lTf CO rH O rH rH O N CO r- 00NCI rHrHr- • rHrHr- . H CM O rH r- CO N O r-H t— 1 1— 1 — 1 1 — 1 I— CO co o- Cl CM O — — - 1- rH lO lO CM ■* CM o oc o o c . o o c o o c o o c o o c CM CM CO CM -* Tt LO LO Tf CO CO O- CO iffl oc O CO -ct CSNN CO rH C£ O i-O c O CO LO OtOHJ i—i CO c co oo c CO lO CO CO t> CM 00 N ■* -# Tt -* ■* 'O *# ■* -=r CO -* Tt ■HTfU^ *# m co LOCON LO LO N rH O-l CO 00 CO CO • 1> 03l> LO CO CM Ci oo co tjh CM CO ■ . co io ^ co oo c- CO LO rj- CM rH CO CM !>• C CM CO C lO 00 >— CO ^ c OHN C0 CO CM LO 00 CM lo N CM ■* T« "O -*-*-* ■# T< LO CO -* ic. CO ^ Tt CM Ol CO rH rH CM rH rH CM Ol rr -* CM CO lO ^H CO co cm oo i-h O 'eff Tf CO LO LO CO CO tjIio • 'cfi -*' ** id CO CM rH CM CO 00 T*' N rH -*' ■ rH rH . rH ^ • rH rH • rH rH CM CM lO . CO • 00 ■ i_o CM co • co • CO • o ■ Ol • CD '■ CO ■ CO ■ o 1—1 '■ T-H ■ i> • '■ T—i '. 1-1 ; ! '~ H y—i ; ,_l ; '-' '. ^ rH CM CO -* rH O) CO -* i— I CM CO ^f rH ca co Tf i— I CM CO ^1 rH Ol CO ■HI rH CM CO ^t< rH CM CO "* ^J j "3 "3 o o o o Ki ca ca e ci o o o o o CJ o o p, ft a +-* H-^ o o o o O ■+^ -Q A g g g g a .g _g ^g '3 '3 '3 '3 "5 u Sr J-t t* f-t ca ca ca a ca 03 C3 a CO CO o p o o o o a .u feH Ph fe CO t- 00 CO o rH CM CO CO 00 CO "# rH CM CO l^ N N co t- oo l> t- l> CO CO rH co CO co co CO 6 6 Q. 6 6 6 6 6 H w H r? H p? H? w cd CD ID 0}

f -+' -t"' -t o i -t- -t- -r e i co -t — CJ oi -t -r co -r -t- -t co -r -r -t PQ _ won 1-711- i^ coa oi -ti cc i~ co -t 1 OS Ifl CO 03 US 1- 1- i> os a Ol -t !£ OS CO 1 - ci-i- 1- coco O H |H — l^H |H ,-H ,- NWC ^ 01 o • o ■taio HMC ■* CO CO co co o os co -* -t >-0 >6 CO O-l CO • i-i Ol CO co -t -t 'OO oc -f >o ec KJCOtO • J? a M O * t-H ^H i— < i 1 ^H f— 1— 1 1— t 1— a M _o t- i-H IM i.O OS c Ol I- -d -f 'C t- CO o o i-i co co • 02 CO -* ■* -* TH IT. t- i^ co -t- 1- c ^H ^H O ^h Ol 01 01 01 Ol 5 o3 r-H t-H i — 1 r— — .— 1— ( 1— 1 1— lO «o t^ o o o o o o • oo o o o c © © c ooc coo ooo t^-. a CO -a § i-H CO 1- O CO o OiOTf CO OCDC KJOOi- O OS >0 l~ O Ol OON ^H O I-. lOOs'-t i-H 0-i rt -t-' d O id © r-i En oj LO«5iO iO LO iC -tf -f "-0 iOOI~ "Q i.O O 1Q CO CO • 73 CD i.O o Ol-t O i-i CD © i— 1 CO OS o tx O OS CC CDO-* CO .-s CO Ol l^iO rCJ CM -f -# t> t- -* -* OJ CO OS t^ © 1-1 rt l 00 - CO ■ l> • ^ i (3 i— I CI co 13 co tH M fl l— l C a .e _a a a '3 '5 '3 "3 '3 '3 Ph ui t-t CO a u u += o3 i> ^ O pq > > 1* •o to Ir^ co © CD "O" o 1* en CO co -* «o> o o T— 1 lO lO lO lO CO co CO CO >C0 ira 6 6 6 6 6 6 a * as co r- CON N OS "O i-H CO N00 CO i-l N 00 OS OS O -* ■* -V Tti iO IO IO 00 CO ■# "# CO i-H (N IO CD CD 00 CI CD ■* «0 "O O iO OS IONH i-H i-H CI CON 00 co io "O i— l CO io CI CI CI CO CD 00 CO CO CO "* CD CI ci ci co CI CI CI o o o o oo o o o oo o o o o oo o © o © oo o IO 00 OS CD »0 i— I 00 lO N o o o IOCO-* N00O0 o co co i-O OS CD LO i-H CI "O CD CD oo co N ■*UJI!J iHCOCS lOiOiO ■-I CD OS IO "O CD IO -* o CD 00 OS *# lO ,-H 00 "#00 os ci co O OS -* IO CD CD CO iO i-H CO 00 N N N CO con N co co co lOOSN co co-* -* NO co cOTt< ci -# © cj ci co CD 00 OS oon 00 OS N co CON CD i-H iocs' ^h 00 OS "O co oo rH i— 1 CO OS 00 CI -*' CD CO • CD • CD • OS ■ OS • OS • O ■ 00 • OS • 00 ■ CO ■ 00 • CI • CI • i-h CI CO •*# --I ci co <* i-i ci co -f rHOIK -* i-H CI CO ■* d '3 03 o o 3 3 O o o o o d a H^ h-4 CD ca d d § § d a ^ M d d S3 c3 30 CONTRIBUTIONS TO THE STUDY OF COAL Analytical Results The banded Lngredienl (samples were all subjected to proximate analysis, including sulfur and B.t.u. determinations (Table I). The analyses indicated certain importanl differences in the character of 1he ingredients. The analyses of fusain are typical of the greal variability of the moisture and ash content of this material as previously pointed ou1 by Pan- and others, 7 due to its porous nature. In mine L, Fi'anklin County (Analyses 23, 24) it may be noted that the moisture content of fusain varies from 8.99 to 22.80 per cent, and the ash content from 4.80 to 16.91 per cent. Air drying loss is high for the same reason. Another note- worthy peculiarity of fusain is a high fixed carbon content, commonly about 75 per cent on a dry ash-free basis. This results in a fuel ratio (F.C./V.M.) commonly between 2.5 and 3.0 (Table 5). The heat value of pure fusain, on a moisture and mineral matter-free basis (unit coal) is commonly about 15,000 B.t.u., although there are erratic variations from this value possibly clue to the fact that occasionally fusain will merge gradually into vitrain. Vitrain is generally characterized by less ash than the other in- gredients, and a relatively low moisture and mineral matter-free (unit coal) calorific value. The composition of clarain does not differ greatly from that of the seam as a whole. The fuel ratio of clarain and vitrain is much less than it is for fusain. but in samples from the same mine the fuel ratio of clarain is found to be lower than that of vitrain. In general there is an increase in the fuel ratio for the bands as well as for the raw coal south- eastward across the southern part of the State (Table 5). Theoretically, unit coal (dry, mineral matter-free) values of stand- ard face samples in a small area such as that represented by the opera- tions of a single mine are essentially uniform, not varying more than 100 units and usually not more than 50 units from a well established value for the mine. Such average values provide a means of determining the probable character of the ingredients as compared with the character of the entire seam. From a general knowledge of the character of clarain it would be expected that the unit coal calorific value of this ingredient would be a little higher than that of the seam as a whole, that vitrain would show a little lower value and that fusain would be above the aver- age. These probabilities are based on supposition supported by observa- tion that vitrain contains less hydrogen than clarain, and that the carbon content of fusain is usual lv verv high. 7 Parr, S. W., Hopkins, H. C, and Mitchell, D. R., Fusain : Industrial and Engineering Chemistry, Vol. 3, p. 64, Jan. 15, 1931. BANDED INGREDIENTS OF NO. 6 COAL 31 Table 5. — Fuel ratios of banded ingredients (Fixed carbon/ volatile matter) County Vitrain Clarain Fusain Washington 1.2 1.15 1.18 1.14 1.11 1.03 1.03 1.06 1.01 1.11 2.0 2.0 3.4 Average 1.16 1.34 1.37 1.06 1.18 2.46 Jackson 2.86 Average . . . . Franklin 1.35 1.54 1.57 1.64 1.18 1.36 1.48 2.86 2.3 9.6 Average 1.58 1.42 5.95 Analyses of face samples and of samples of the banded ingredients from mine E. Washington County, mine K, Jackson County, and mine L, Franklin County, are available for comparison. The data (Table 6) indicate that for these three mines, at least, the unit coal B.t.u. value of vitrain averages less than, and that of clarain about the same as, the average B.t.u. value for the seam in each case. The values for fusain are exceedingly irregular, so that averages mean very little, but it is apparent that values may be very high. The point to be made is that there is some possibility of variation in heat value of the prepared coal due to the concentration of one or the other of the ingredients in one or more of the fractions. 32 ro.vnuiir I'KiNS to r r 1 1 1-. mi nv <>!■ C0A1 S s s ^^ d co -r co co Ol Ol ,-i pH ^r, -.-. - 1 - 1 (5 to © -f -+i >-H CO CO IO O LO ssi 03 o © to © CO >o OJ CO © © 50 CO ■* ■<* co 1—1 1 — 3 t— r* T. co 1—1 "3 CO CO I> a- CO Ol Tt ** "# ■* CC 'O ■* ■* "3 1— 1 t-H T— 1—1 3 CO of c lo cc i— rH LO co t-h"© t~ rs ■* © -t © CO co CO o CO © © co co cm -d Ol c t^ LO lo LO co lo © > -* -* Tf -* t( ■* ■* ■* ■* ■3 1— 1 r-H 1— T— 1 T— i-H i-H i-H T— 1 i — 1 1— 1 1 — i B of co" i> th"c l-O" ■* LO C o" ,—7 tC ©" -p ©co t^ ooc ■* © © c LQ LO -* o -t< lOCO^t coco © Th © i.C LO LO •^ © CO ■sH ■* tJ '"* CC •* -f -f -t tH -* ^* ■* Ol h i> o 5 OC ) co c B r-H r- a © ©ot- " © OT to O) l^ | © CO ^H c<- ) LO >. oo"©"cv r i-h o- ) -tl lo ^ i— T rf © ©co t^ co t- '. Ol © . © © .-h © O o3 B CO CO c - > co c -^ ^t< lOiOiO I>-"lo"C -*"o NNCDiOC of t^ co" co ©" co" l o" © t^ t^ l-~l> OOiOiOir © O © O i— i o o CO CO c > co a ) © © CO CO C Tf io -^ to lo iO lO 66c 6c c " 1 -^ ;£ :£ c 'co CO CO O o O o ■> o p. Ph o, a. z. oC B.£ '2 £ +s 1/ o r a c B (Com itrain . larain a c B e o (Com itrain , larain usain . E=H>C m^ fin >OP& fe fo >Ofe >> B +^ p B B "5i B o CO _B o 3 ( J 2 ^ CO M 3 the weight pins tlic sum of the weights preceding in each case) is used as ordinate and the correspond- Table 7. — Comparison of the coals at 5 per cent recovery intervals Sample Coal recovery Ash B. t. u. value] (dry) B. t. u. recovered B. t. u. increase A Per cent 100 95 90 85 100 95 90 85 100 95 90 100 95 90 100 95 90 85 80 100 95 90 85 100 95 90 85 100 95 90 100 95 90 100 95 90 Per cent 13.62 10.6 9.0 8.0 13.45 10.8 9.1 8.0 13.37 10.0 8.0 12.24 9.5 7.8 13.82 11.5 9.8 8.5 7.6 14.28 10.3 8.5 7.5 15.05 11.2 9.5 8.1 9.85 7.2 6.5 10.26 7.5 6.5 9.29 7.0 6.2 11,756 12,300 12,580 12,720 11,796 12,200 12,500 12,650 11,791 12,350 12,850 11,533 11,750 12.350 11,743 12,150 12,420 12,600 12,780 11,615 12,400 12,680 12,820 11,698 12,320 12,680 12,850 12,743 13,200 13,300 12,778 13,150 13,325 12,933 13,300 13,475 Per cent 100 98.6 96.0 92.0 100 98 9 96.0 91.0 100 99.5 97.5 100 99.8 97.0 100 98.5 95.1 91.5 87.2 100 98.2 97.5 93.4 100 99.5 97.2 93.0 100 98.5 94.0 100 98.0 94.0 100 98.0 94.0 Per cent 7.0 B 6.0 c D 9.0 E 7.1 5.8 F 9.1 G 8.4 H I 4.4 J 4.3 4.2 BANDED INGREDIENTS OF NO. 6 COAL 35 ing determined B.t.u. as abscissa. This curve shows the heat character- istics of the coal sample from the lightest to the heaviest fractions, and reveals the extremely low heat value of the heavy fractions. The Coal Eecovery-B.t.u. Recovery curve is constructed by using the coal weight per cent of the fractions as ordinate and the corresponding cumulative B.t.u. per cent as abscissa. This curve when used with the Coal Recovery-Ash and the Coal Recovery-Sulfur curves reveals the con- ditions most favorable for separation from the standpoint of quality and maximum recovery. As a further demonstration of the value of B.t.u. distribution data when used with the conventional float-and-sink information, a table has been prepared (Table 7) showing the effect upon B.t.u. recovery of each 5 per cent decrease in coal recovery until 6 to 8 per cent ash is reached. A tonnage rejection of 10 per cent (90 per cent recovery) entails a heat loss of 2!/2 to 6 per cent, representing the fuel discarded. But there is an improvement in the quality of the coal of from 542 to 1,065 B.t.u. per pound (4.2 to 9.1 per cent), the improvement for coals from areas outside Franklin and Williamson counties being somewhat greater than that for the coal from within these counties. Natural low-ash coal such as from mines H, I and J, lose more heat value as tonnage recovery is lowered by refuse rejection than do high-ash coals because of the relative- ly larger amount of coal lost. Regional Variation The ten coals to which this investigation applied represent the two most important varieties of coal mined in Illinois from the standpoint of production, namely the coal from southwestern Illinois mined in the Belleville and Standard districts and the coal from the southern Illinois Franklin-Williamson district. The Herrin (No. 6) coal in the southern Illinois field is slightly higher in rank and lower in ash and sulfur than the coal from this same bed in southwestern Illinois. The unit coal calorific value of the coal in southwestern Illinois varies from about 14,350 to 14.450 ; that in southern Illinois from 14,500 to 14.700. Mines A to G inclusive represent coals in southwestern Illinois ; mines H, I, and J represent southern Illinois coals. Certain similarities are found in the curves of each group of coals so that in discussing briefly the characteristics of the curves it is convenient to group them geographi- cally. A summary of the float-and-sink data appears in Table 8. 36 CONTRIBUTIONS TO THE STUDS OF COAL pq Ph o d 02 o '°. o -t; a PQ iHNOoeoooMm-tcc OrtHl.fflf -fC/jOO oocx>T-icoi-(t~co05t»-35 O" ©' r-i O O O* O ©' ©' © H 3 S3 3 CO l-OJOCII M — i -r< i-h O CO-t>CO-* '5 iN-fioowHoo-f ra co n o co to n -t >n ■* t)< o d co © 1(3 CO T— < 3 pq ©COOOiiOCOGOOOCO^HOl -* CO 1 - ~ C~.-l"0-tO t^COMCrtCONCBNCC CO tsN^oionocc-HO co-t CO i(3 >o O CO J5 '3 cooiroiowjOMcoioio o d CO © CO 3 pq Oi-isoonocamoo CO 'O KJiOHNtNCOMM lO CM ■* CO 00 >0 CO N O N Of of Of of i-H of of of co" of 3 "3 CO '■fO-#03L~010l01©'"cH .d CO CO^OOCOC33i-it^.oOOt^ OOOONCMOOOlfflMO '3 HiOMOONOOlOiOCa ■* H O ffl CO U5 ■-< CD CO CO IMNrtH Ol CM i-H CM i-H o d co © 00 d j3 co co CD 6 pq lOCO'cHiOOOt^OOCOCDOl Ol CO Ol 20 O ^-i CD CO l^ X0 MNINCO'-ICOMCDCON co" co" co" of co" co" co" co" co" co" 3 CO H ■* N ■* lO N tH M O CM MOSMMCOMHHHH CO t^COTtHOl^C3202000CO Tt '(3 1(3 © i(3 CO Oi-h OO 1 -o • (J 3 co" r-f f-fesi ~ pq d CO ooco©>c3i-coco-. go-to 3 O CO CO CO i— 1 01 ~h CO -f oo cici«rjc;irt © 3 Ol CO ~ 3 ■" CO © GO CO "(3 CO OO CO Ol -f hi _S 1(3 © © CO CO CO CO '(3 1 - CO CD 1> o +3 "3 CO © Ol CO I- Ol CO Ol l- UO ONi"t b- 1^ Ol CO i-l CD P= '3' © o ©00 >o © CO Ol o oo© 3 CO' co' t^-' oo" +3 pq t^CX)Ol-*CO©-*rtlO>00 3 KJ CD CO CO K3 K3 iH CM i-l CO o "3 o. CO CO © oi ©CDt^i-ix3-*CMCOiO© o -3 NiO-tCONCDOOONN - H "H TjfcOOlrH^OrtCMOffi © ■3 HOOrtCMONMCOn <1 cocooicococococococo +3 OlO^OOOCOiOCMCOOl bjD lO^COLCOCDCOCOCOOlOl QJ CD ^fQOflHhOK"^ P. s 03 £ CO BANDED INGREDIENTS OF NO. 6 COAL 37 Southwestern Illinois Group coal recovery-ash curve The A curves for these coals show a change in slope toward the lower end at 85 to 90 per cent recovery. Cleaning of such coals to pro- vide a low ash content (about 8 per cent) commonly necessitates a loss of weight of about 10 to 15 per cent. (Figs. 8, 9, and 10.) ASH DISTRIBUTION CURVES The curves of Ash Distribution for the group are fairly regular, in general not having the sharp change in direction indicative of an easy separation of coal and mineral matter. These curves, therefore, like the Coal Eecovery-Ash curves, indicate a disseminated distribution of the mineral matter in the coal. The D curve for mine B is exceptional in this group as it indicates a rather sudden increase in mineral matter at the 80 per cent recovery point. REFUSE REJECT-ASH CURVES The Refuse Reject-Ash curves in this group of coals are like the curves last described only moderately concave upward for the same reason. SULFUR CURVES In general the sulfur curves of these coals indicate high pyritic sulfur content and break sharply in the portion representing the heavy fractions. Cleaning, even at high gravities with minimum loss in weight of the coal, would materially reduce the sulfur content, particularly when the sulfur content exceeds 5 per cent. B-.T.U. DISTRIBUTION CURVES- The B.t.u. distribution curves are based on values either determined in the laboratory or by extrapolation and represent the calorific characteristics of any portion of the coal from the lightest to the heaviest fractions. The C curve in the southwestern Illinois group flattens markedly at about 90 per cent recovery thus indicating that the increment beyond this point has little calorific value. This is in con- trast to the curves of the southern group which cross the 90 per cent recovery line with a somewhat higher B.t.u. value and maintain their steepness beyond 90 per cent recovery. :;s C0NTRIB1 TIONS TO THE STUDT OF COAL 2000 13000 I 4000 ASH OR B.T-U-% 10 SULFUR % 5 Fig. 8. Washability curves of Mines A, B, and C. BANDED INGREDIENTS OF NO. 6 COAL 39 Fig. 9. Washability curves of Mines D, E, and F. 10 CONTRIBUTIONS TO THE STUDY OF COAL COM, RECOVER! B.T.U. RECOVERY CURVES The Coal Recovery-B.t.u. Recovery curve is a straighf line with a sharp break at the end; this break for the group under consideration generally lakes place at aboul the 90 per cenl recovery point indicating thai there is relatively little heat loss in the first 10 per cent of reject. This supports the interpretation of curve P> and the general conclusion that the main benefrl in cleaning these coals will he derived by rejection of not more than 10 per cent. It is thus shown that 10 per cent tonnage rejection does not entail a like loss of the available B.t.u. ; curve E indi- cates that 95 to 98 per cent of the B.t.u. is retained at ninety per cent tonnage recovery for the coals tested. T U (DRY BAg 9000 I 1000 13000 14000 MINE G A- COAL RECOVERY -ASH S- COAL RECOVERY - SULFUR D- ASH DISTRIBUTION R- REFUSE REJECT - ASH 5C -SPECIFIC CRAVIT Y B-COAL RECOVERY - B.T. U. C - B.T U DISTRIBUTION E-COAL RECOVERY - B.T-U RECOVERY ASH OR BTU % SULFUR % S Fig. 10. Washability curves of Mine G. Southern Illinois Group washability curves The curves A, D, and B contrast with similar curves for the coals from southwestern Illinois in having sharper breaks, indicating less dis- seminated ash. The amount of mineral matter can be reduced but little without considerable coal losses. It is probable that rejections greater than 5 per cent are not practicable for the coals tested. (Fig. 11.) As indicated by the S curves, the sulfur is evenly disseminated through the coal and no material reduction can be expected by washing. CALORIFIC VALUE CURVES The calorific value curves (B, C, and E), show that a rejection of 5 per cent refuse has little effect on the B.t.u. values but rejections greater than this amount entail considerable heat loss. BANDED INGREDIENTS OF NO. 6 COAL 41 [DRY BASIS; 8000 9000 000 12000 ASH OR BT.U.% 10 SULFUR % 5 MINE H A- COAL RECOVERY - ASH S - COAL RECOVERY SULFUR D - ASH D IS7RIBUTI0 N R - REFUSE REJECT - ASH S C - SPEC FIC GRAVI7 Y B- COAL RECOVERY - B T. U. C - a T U DISTRIBUT ON E - COAL RECOVERY B.T.U RECOVERY I Pig. 11. Washability curves of Mines H, I, and J. 42 CONTRIBl TIONS Mi TIM Ml iiy OF COAL Specific ( Ib lvity The specific gravity curve shows the specific gravity at which a separation musi be made in order to obtain a product of the desired ash content or heating value. SUMMAKY AND CONCLUSIONS Herrin (No. 6) coal of the Illinois coal basin is a normal handed bituminous coal containing- the usual handed ingredients, vilrain. chimin, fusain, and durain, usually only the first three but in places all four, and mineral impurities. When the coal is crushed to small sizes (minus Vi inch in these experiments) the banded ingredients and the impurities are separated and appear in more or less discrete particles. However, the foremost problem in the improvement of the coals is that of removing the mineral impurities, the effect of which is measured not merely by the loss in tonnage or the improvement in ash content, but also by the effect on the heat value of the coal. The coals of southwestern Illinois investigated in this series of tests have an average ash content of 13.7 per cent and can be cleaned to an 8 per cent ash content by rejecting 10 to 15 per cent of the tonnage as refuse. The coals from southern Illinois (Franklin- Williamson district) that were tested can he cleaned to a 7 per cent ash content by rejecting 5 per cent of the tonnage or to 6.4 per cent by rejecting 10 per cent. In general 25 per cent of the total sulfur can be eliminated in the southwestern Illinois coals tested when cleaning is carried out at 85 to 90 per cent recovery, whereas in the southern group only slight sulfur reduction can be expected from mechanical cleaning. It is generally recognized that an important advantage of cleaned over uncleaned coal is its higher B.t.u. value. The variations in B.t.u. value in coal subjected to the cleaning process are therefore of interest and have received particular emphasis in these studies. The series of curves that have been constructed showing the nature of variations in the heat value of different fractions of the coal provide a means, in addi- tion to the usual washability curves, for determining the most desirable point for separating coal from ash and sulfur and in standardizing the B.t.u. of the coal as it is marketed. It was found that in cleaning the coals of the southwestern Illinois group to about 8 per cent ash the average tonnage recovery was 87 per cent. The B.t.u. recovery, however, was 94.2 per cent and the heat value of the clean coal was increased to 12,671 B.t.u. (dry) as compared with 11,704 for the uncleaned coal. In addition to the improvement in the BANDED INGREDIENTS OF NO. 6 COAL 43 fuel due to the ash and sulfur removal, the cleaned coal contains 8.3 per cent more heat than the coal that has not been cleaned. Cleaning the coals in the southern Illinois group to obtain a 90 per cent recovery provides a coal with 6.4 per cent ash, and 94 per cent of the B.t.u. is recovered. The average dry B.t.u. of the cleaned coal is 13,366 as compared with 12,818 in the uncleaued coal, an improvement of 3.5 per cent. These results of float-and-sink tests on representative samples of No. 6 coal from various mines in southwestern and southern Illinois indicate in only a general way the possibilities for improvement of these coals by mechanical means. The data presented for any particular mine are in themselves insufficient basis for establishing cleaning procedure. Extensive sampling and testing of the sizes to be mechanically cleaned should precede any decision in regard to the type or capacity of a clean- ing plant which will best meet the needs of a particular mine. The attention given in this report to the banded ingredients in coal No. 6 is in line with the emphasis placed on the fundamental constitution of Illinois coal in investigations that have been carried on by the State Geological Survey during the last four years. There is an increasing realization of the heterogeneous constitution of our coals, and that they are composed of several distinct materials rather than of a single sub- stance. The float-and-sink tests for determining the washability of coals provide additional evidence, beyond that furnished by concurrent micro- scopic studies, of the lack of uniformity in the character of the material and of the tendency of different ingredients to accumulate in the different fractions in proportions quite different from those in which they occur in the coal as a whole. That this would probably be the case is more or less obvious, if once the heterogeneity of the coal material is realized. It is one purpose of the present report to encourage this realization. With respect to the banded ingredients of the coal, the present tests and others that preceded have shown that fusain, and to a less extent vitrain, breaks into small particles in the mining and preparation processes and tends to become concentrated in the "carbon" sizes. Fusain is largely removed in the minus 48 mesh material, which was not subjected to the float-and-sink procedure in the present series of tests. It was found that concentrations of vitrain of 71.3 per cent can be obtained in the coal floating at 1.30 specific gravity, whereas the fractions 1.35 to 1.70 contain 91.7 per cent of the clarain. In American practice, there is little practical application made of the effect of variations in amounts of coal ingredients on the use of coal. Such applications are confined almost entirely to the regulation of fusain in coal used for coking purposes. Such regulation may consist of (1) 44 CONTRIBUTIONS TO THE STUD'S OF l 1'iisiiin l>\ removal ol' sizes in which it lends to concentrate (dedusting) or (2) careful mixing practices to ovoid so^re^o t i n 1 1 ol' this constituent. It is now fairly common practice in holh wet ond dry cleaning processes to dedusl ond so remove the I'usoin which is concen- trated in the line sizes. 8 It is noteworthy that in a few coses Kuropeon preparation is eonsiderohh more advanced c lerciolly, permitting the rearranging of the component parts in combinations other than in those in which they occur in the seam. It is with the belief that, with increasing scientific information in regard to the nature of the coal and its components, such preparation may promise a profitable procedure in the near future, and with the hope of stimulating further researches in the possible separation of these ingredients and their effect on the utilization of coal, individually or in certain definite proportions, that the results of these cleaning tests have been included in this report. s Hebley, Henry F., The Dedusting of Coal, Transactions A.I.M.M.E., Vol. 108, Coal Division, 1934, p. 88-127. A PRELIMINARY REPORT ON UNIT COAL-SPECIFIC GRAVITY CURVES OF ILLINOIS COALS Outline Page Introduction 47 Unit coal-specific gravity curves 50 Mine sampling and laboratory procedure 50 Plotting of data 51 District curves 52 District VII 52 District VI 54 Significance of data 55 Variations in the coal substance 55 Role of mineral matter in curve variation 56 Factors of analytical procedure in curve variation 56 Figures 1. Dry coal calorific value-ash curves 48 2. Map showing location of mines sampled and areas of districts VI and VII 49 3. District unit coal-specific gravity curves, by mines 51 4. Graph showing comparative values for fresh (Ei, E 2 , E 3 ) and stored (E) coal. ... 52 5. Graph showing relation of values for vitrain (VEi, VE 2 ) and head samples (Ei, E 2 ) from the same mine to dry coal calorific value-ash curves 53 6. Unit coal-specific gravity curves based on duplicate portions of the same sample. . 54 r 45 ] A PRELIMINARY REPORT ON UNIT COAL-SPECIFIC GRAVITY CURVES OF ILLINOIS COALS* By L. C. McCabe, 1 D. R. Mitchell, 2 and G. H. Cady 3 INTRODUCTION For purposes of classification, the relative constancy of the pure coal substance is assumed. This assumption has been carried to the extent of constructing a dilution curve 4 based on the determined B.t.u. and ash content of the coal. It is generally concluded, from empirical data, that this dilution curve is essentially a straight-line curve: The dilution curves for the coals under consideration are shown in figure 1. The dry ash and B.t.u. values of the series of float-and- sink fractions were used in establishing the points which determine the direction of the curve. Space does not permit the consideration of each curve in detail but some characteristics which are common to almost all the curves may lie pointed out. By referring to Table 1 and figure 1 it may be seen that the intermediate fractions of 1.35, 1.40, and 1.50 specific gravity, which constitute the greater weight per cent of a given coal sample, fall more frequently on a straight dilution line than do the lighter or heavier frac- tions of the same sample. In most instances there is a marked steepen- ing of the curve between the 1.35 and the fraction of lightest gravity (1.30). In general the curve also increases in -steepness between the fractions of 1.50 and 1.70 specific gravity. Grtinder 5 pointed out the deviation of high-ash fractions from a straight line, and Thiessen and * Presented before the American Institute of Mining and Metallurgical En- gineers, New York Meeting, February 1934. 1 Assistant Geologist, Coal Division, Illinois State Geological Survey. 2 Assistant Professor, Mining and Metallurgical Engineering, "University of Illinois, Urbana. 3 Senior Geologist and Head of Coal Division, Illinois State Geological Survey. 4 Brinsmaid, W., The amount of inert volatile matter in mineral constituents of coal: Jour. Ind. and Eng. Chem., Vol. I, p. 65, 1909. Stansfleld, E., and Sutherland, J. W., Determination of mineral matter in coal and fractionation studies of coal: Trans. A.I.M.E. Coal Div. pp. 614-626, 1930. 5 Grtinder, W., Waschkurven and heizwert, Gliickauf, Vol. 68, pp. 114-119, Jan. 30, 1932. [47] 48 CONTBIBl I kins TO THE STUDY OK ro.W. Reed 8 have recently indicated ar apparenl uncertainty of points repre- senting low-ash fractions of Illinois coals. 12 18 24 ASH PERCENTAGE (DRY COAL) Fig. 1. Dry coal, calorific value-ash curves. It will be noted in figure 1 that the head samples invariably occupy a position above the dilution curve determined by the corresponding Thiessen, G., and Reed, F. H., Studies of the graphical method for calcu- lating pure coal calorific values. Fuel Vol. 13, pp. 168-175, 208-217, 1934; Illinois State Geological Survey Report of Investigation No. 32, 1934. UNIT COAL-SPECIFIC GRAVITY CURVES 49 Fig. 2. Map showing locations of mines sampled and areas of districts VI and VII of the Illinois Mining Investigations. 50 CONTRIBUTIONS TO THE STUDY OP COAL float-and-sink fractions. Caw lev 7 and Gooskov 8 have gone beyond the scope of this paper in determining the cause of the apparent deteriora- tion of coals floated in organic solutions. UNIT COAL-SPECIFIC GRAVITY CURVES The dilution curves (Fig. 1) provide a variety of ash- (or min- eral matter) free values depending upon what portion of the curve is projected as a straight line to the O-ash boundary. For this reason consideration of the unit coal values (Parr formula) 9 of the fractions obtained by float-and-sink method was desirable. Mine Sampling and Laboratory Procedure The mines A to L inclusive (Fig. 2) all operate in the Herrin (No. 6) coal in southwestern (A-G) or southern (I-L) Illinois that is. in districts VI and VII of the Illinois Mining Investigations. 10 A standard channel sample from roof to floor was taken for the float-and-sink tests. Nothing was excluded in taking the sample except in the case of mine E in Washington County where the clay "blue band" of No. 6 coal has an abnormal thickness of 8 inches and was not included in the sample. All samples tested in this study were ground to minus 14 inch. In the first series of samples, eighteen to twenty months expired between the date of sampling and the date of analysis. In the second series of samples (three samples from mine E) analysis was within two weeks of the time of sampling. Float-and-sink separations were made using mixtures of benzene, carbon tetrachloride, and bromoform following the procedure used by Callen and Mitchell. 11 In the first series of samples, fractions floating in liquids of specific gravities 1.30, 1.35, 1.40, 1.50, 1.70, 2.0, and the fraction sinking in the 2.0 solution furnished the material for analysis. In the second series of samples from mine E in Washington County, 7 Cawley, R. L., Notes on the determination of the calorific values of high-ash coal : Fuel, Vol. 11, No. 8, pp. 302-303, 1932. Cawley, R. L., Notes on use of different media for float-and-sink tests on coal: Fuel, Vol. 11, p. 303, 1932. 8 Gooskov, W., An experiment on parallel float-and-sink testing in carbon- tetrachloride and zinc chloride: Colliery Guardian, Sept. 16, 1932, pp. 517-518. 9 Parr, S. W., and Wheeler, W. F., Unit coal and the composition of coal ash : Univ. of Illinois Eng. Exp. Sta. Bull. 37, 1909. 10 Preliminary report on organization and method of investigation : Illinois State Geol. Survey Cooperative Mining Investigations Bull. 1, p. 12, 1912. "Callen, Alfred C, and Mitchell, David R., Washability Tests of Illinois Coals: 7niv. of Illinois Eng. Exp. Station Bull. 217, p. 32, 1930. UNIT COAL-SPECIFIC GRAVITY CURVES 51 float fractions were removed from solutions of 1.275, 1.30, 1.35, 1.40, 1.50, and 1.70 specific gravity. The fraction sinking in the solution of 1.70 specific gravity was the end of the series. SPECIFIC GRAVITY Fig. 3. District unit coal-specific gravity curves, by mines. District VII (Belleville), Mines A-E. District VII (Central), Mines F-G. District VI (Southern), Mines I-K. District VI-VII boundary, Mine H. Plotting of Data A curve was plotted for each sample with unit coal values as ordin- ates and specific gravities as abscissas (Pig. 3). Data representing values obtained from different samples from the same mine produce similar curves. The chart shows two small groups of characteristic curves, each group representing samples from adjacent mines, suggest- ing the possibility that a distinct type of curve may characterize the coal in each district. 52 CONTRIBl TIONS TO TIJIO SI I in OF com. District Curves DISTRICT VII District VII embraces a part or all of fifteen counties (Fig. 2) in the southwestern part of the coal basin. The curves for this district (Fig. 3) fall into two separate groups; A, B, C, D, and E from mines in St. Clair, Washington, and Randolph 14,000 O 13,750 Fig. 4. Graph showing comparative values for fresh (Ei, E 2 , E 3 ) and stored (E) coals. counties taking similar form and comparable positions while F and G, from mines in Macoupin and Montgomery counties respectively, assume a lower and different form on the graph. UNIT COAL-SPECIFIC GRAVITY CURVES 53 The A-E curves are distinguished by a flattening or reversal in direction caused by a low unit B.t.u. in the fraction of 1.35 specific 4 VE, ° vE £ BE 2 w< \"E, o FLOAT AND SINK FRACTIONS • HEAD SAMPLES aVITRAIN SAMPLES \\ \ E 2 ASH PERCENTAGE (DRY COAL) Fig. 5. Graph showing relation of values for vitrain (VEi, VE?) and head samples (Ei, E 2 ) from the same mine to dry coal calorific value-ash curves. gravity relative to the 1.40 fraction. This is only barely perceptible in the G-curve which is geographically farthest removed from the A-E r.-i CONTBIBUTIONS TO THE STUDY OK COAL group. The F-curve which is derived Erom a sample intermediate be Iwccii the Gr-sample and the A-E group flattens considerably in the frac- tions of 1.35 and 1.40 specific gravity. As noted above, resampling of mine E in Washington County was undertaken to verify results as there had been a considerable lapse of time between sampling the mines and analysis of float-and-sink frac- tions and head samples. The results of this check are shown graphically in figure 4. Curve E of figure 3 is reproduced in figure I to facilitate comparison with the curves of the check samples E ; . E 2 , and E g . Jn \\ L.\ \ SPECIFIC GRAVITY Fig. 6. Unit coal-specific gravity curves based on duplicate portions of the same sample. general form and relative position of fractions, the four are similar with the exception of the low position of the 1.40 specific gravity fraction of curve E 2 . The markedly lower position of curve E in relation to the other three is undoubtedly due to oxidation in storage. DISTRICT VI District VI, with mines for the most part operating in 'No. 6 (Herrin) coal, produces a greater tonnage than any other district in the state. The mines sampled are all in the ISTo. 6 seam. UNIT COAL-SPECIFIC GRAVITY CURVES 55 Curves I and J are based on data obtained from samples in mines that are only a little more than a mile apart whereas the mine represented by sample K is about 7 miles to the south. Although there is no marked parallelism in form in this group, the differences are small and the group is confined to a narrow range and to a distinct position with relation to the other curves. Curve H, which represents a sample from near the boundary of dis- tricts VI and VII, occupies an intermediate position between the two groups. The curves L x and L 2 (Fig. 6) are constructed from data obtained from a single sample collected in mine L ( Pig. 2 ) , in the northwest part of district VI. The sample was riffled into two equal parts which were carried through the float-and-sink and analytical procedure as two separate samples to test the possibility of duplicating results on identical materials. SIGNIFICANCE OF DATA Although the purpose of this paper is to present the data obtained, there are certain implications which might be of value in further study of this problem. The variations in the curves of figures 3 and 4, as well as those ob- served in the dilution curves (Fig. 1), may be due to one or more factors. Those which appear to be pertinent to this problem are ( 1 ) variation in coal substance with change in specific gravity, (2) variation in kind and quantity of mineral matter with the specific gravity of the fraction. (3) factors of analytical procedure which tend to introduce error in analysis, particularly in high-ash and high-sulfur fractions. Variations in the Coal Substance Advances in microscopic investigations of coal have revealed that a considerable range of materials enters into the constitution of almost ail coals. These studies indicate that not a single "pure coal" but num- erous "pure coals" comprise a seam. It is shown in Table 3 (p. 16) that the separation of Illinois coals into several well chosen gravity fractions by float-and-sink methods tends to concentrate vitrain in the light, clarain in the intermediate, and pyrite and other mineral matter, and to some extent fusain, in the hea.vy fractions. A 7 itrain concentration in the fractions of 1.275 and 1.30 specific gravity appear to be responsible for the initial steepness of the curves of figures 1, 3, and 4. This is substantiated by plotting the pertinent data 56 CONTRIBUTIONS TO THE STUDY OF COAI. of available vitrain samples on figure 5. When the two channel samples E x and E 2 were taken, vitrain samples corresponding in locality were secured. These hand-picked villain samples are identified with the dilution curves of figure 5; e. g., the channel sample furnishing the curve E x and the vitrain sample whose position on the figures is [lumbered VE X are from the same locality in the mine. The position of the vitrain is above the curve of the fractions from the same room. This is possibly due to the fact that the vitrain was separated by hand and was not sub- jected to the apparent deteriorating effect of organic solutions. A more complete treatment of the chemical significance of the constituents ap- pears in another place. The Bole of Mineral Matter in Curve Variation No detailed information on the nature of the mineral matter as distinguished from ash. is available for the fractions separated. In the heaviest fractions (2.0 sink) pyrite, calcite, kaolinite, and undifferenti- ated shale particles are present. Further investigations which might have some bearing on this phase of the problem are (1) the possibility of regional or district mineral suites, (2) the variation in the nature of mineral matter from fraction to fraction within the same sample, and (3) the relationship of mineral derived C0 2 to the B.t.u. values of the fractions which determine the curves. Factors oe Analytical Procedure in Curve Variation Considerable difficulty is encountered in determining the B.t.u. values of high-ash and high-sulfur fractions. The difficulties in calori- metry undoubtedly contribute to the marked decline in B.t.u. in the 1.70 specific gravity fraction and consequently are in part responsible for the terminal steepness of the curves of figures 1, 2 and 3. UNIT COAL-SPECIFIC GRAVITY CURVES 57 » Eh oo co o ci o • co C5 (35 (35 © GO t- IHOOH IN CM O 00 o tO CO CO *0 IO CO CO CO l^ CO io "3 i-H C~. 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