A STUDY OF THE COMBUSTION OF ORGANIC MATERIALS IN CLAY By ALBRA HENRY FESSLER THESIS FOR THE DEGREE OF BACHELOR OF SCIENCE IN CERAMIC ENGINEERING COLLEGE OF ENGINEERING UNIVERSITY OF ILLINOIS 1921 Digitized by the Internet Archive in 2016 https://archive.org/details/studyofcombustioOOfess NOV V- UNIVERSITY OF ILLINOIS Juxi.e...!. 19121. THIS IS TO CERTIFY THAT THE THESIS PREPARED UNDER MY SUPERVISION BY ALBRA ENTITLED A.. C,OOUSTI ,111 CLAYS IS APPROVED BY ME AS FULFILLING THIS PART OF THE REQUIREMENTS FOR THE DEGREE OF MCir^LO.B. .QE S.C.IEH.C2I 476y?-i iiir. - > ? V ^noviLuiHo me^avMU i... »> ^ i. ♦ r; YH Hoiaivaa^iuii iU vi3jH r » V* -* 4 - *m* 4 » r ^ ' t*f . » i I# * ’ r vtiu ■ .*-ii«>.V . ^■ •.■.^..-v,.at •?:'%*’ «• ■ f Vi W ■' .* ■ f /' ‘ j» ’ .* >![••■ jj a . «*• V v^ i ^gjfin «• .^r.. ✓. »v lOTi; ’j >JHi ;r.;ii,iajrjrfftrvai^vuiU mk f f%ii ' ' ' ' ? ' i ’:'v- ' '•►■ Ijl' :,'|}^ . . . ;.. HU ‘-t i>i 03 U -.•a . y ^ • |<#y , -i. . '..^.% /osa f .1 ^ ■ \% '■ fc X’ aiX r. 4 . '« ' ? 7 . \ ♦« tt||) • - 4 i«X # A--» iic'v- ar-i£>.J& , -^-hs'''S.' ‘''-i-tl ' j .'jy Trjl^^^t'»y.>jra-HqaA3ii , . ' fim ^ T/iBLE OF CONTENTS I INTRONIJCTICN Page (a) Carbon in clay.... 1 (b) Iron in clay 2 (c) Critical period in burning. 2 ( d) Steam. . 3 II EXPERIMENT. ^ (a) Peterminat i on of the carbon content of the clay.... 3 (b( Principle of the method 5 (c) Apparatus and method 5 (d) Procedure 7 (e) The use of MnO,, as an oxidizing agent 7 III RESULTS (a) Pis cuss ion of results 9 (b) Summary 9 IV BIBLIOGRAPHY 1. E. Orton, Trans. Amer . Cer. Soc . Vol.5, p.377 (l903) 2. J.W.Mellcr, Trans .Eng . Cer. Soc . ” 16, p. 259 (l916) 3. A.Hcpwood & ¥. Jackson, Trans. Eng. Cer. Soc. Vol.2 ,p.93 (1901) 4. Scotts Standard Methods of Chemical Analysis 2nd . Vol . p . 105 . T IITTRODUOTIOU The presence of organic materials in clays and their importance in the burning behavior of clays has long been a knov/n fact. It was noticed that burning clays with high carbon content presented a very different problem from burning clays with lov/ or medium percentages of carbon. In some cases v/here the carbon was very high the kiln would "burn itself" after a dull rod heat was obtained. If the burning v/as not under absolute control at that point the kiln would over-burn causing a total loss of the contents. Another peculiar circumstance in burning clay which is attributed to the presence of carbon, is the presence of a black core in the interior of the finished product. These cores may be due to carbon or to ferrous iron, or both. They may thus be developed in clays with no carbon but with a high iron content.^ The burning of such clays presents a very interesting problem and one that must be v/orked out -for each clay. (^) _Ca_rbon in clay .- Carbon in clays occurs in a form closely allied to bituminous coal or as partially decayed vegetable tissue, such as roots and leaves. This starts to burn as the kiln attains a dull red heat. The vegetable matter burns readily and with no danger to the v/are. All of our burning troubles are caused b^ tia.e bituminous form of carbon. This form! of carbon gives off a combustible gas which will burn on the surface of the brick if enough is present. This causes a rise in temperature which is not desired at this point. Experiments show that brick v;ith 5^ sawdust shov/ no core at the end of 45 hours burning but with coal, t}ie core trn^BSm -irMcyakTtac-,; f i ■ ,»« ' « » - -j* *\ * ‘■.'T r-v- ■ r.'i i- • *!?;• ..-O^-V - W-* . ‘.G ^!.-L Ixi . -T o 1 «ji;Jli'ii5t(ja n>, •j . - ^ *■* 41 *. v*C'r *Ci» ^ / - • « I'J . t '■*\. ' ’ T ^ r * ] *-•» I “'2 /bi>?i,.‘ 24? -in' : £^^'i . ^^■’LV c ^5rvo-i:'4C fil .?r- ./ •t-W'?' • I n 20 i\A _^'; . j** ■ ... ^ '•/iwij t<:< z . k i ’t' .♦■ . O i ;£ : 'i r ^ t ■t T ‘ .r ,. -. „ * ■ . -^^ ; ' 'viiv^ ^rff 1 * -V' '•'• "Vr i ii*l ^ . Ou:^ 2 iv i V - c-'t -V >> £>»j;ia' 3 r 7 t- . *■' .u,’\i: ■- • *• > ■ .3 - "■ r- - I. * }J3 d>;r ? ‘ . '' vlTii^' ' x\: ■• 2 ,dl^ * &;» 9 £ £4 . .1 > ^ , I ./» . -•.v:,b-,V-;.'Ji£i,' ■’ # * • ‘ W i 1 IS :V- i*'. it ^ >, j f .ri I.V-?.T 1 i i: . ‘’j'?'’ ' X '' r?» -■ -'^4^!' 4 V •'r..,..». . »)»■;■••:•• -.‘rvi fc. : ,. -•■.I .Mi ; . ...v..- ■ .L. "Si :i;. . . « j OJ i«ii®w wi> I • 'v»!,-,v • v 5 .y ’'A' l?e» - iif.fl a t<3- •»i • . • #. if ff’H?!. Xp urf X uA>t; !• M w 0 «>: Mf..' liX'rr Xai' 1 I i; lii T -a 4 • kj|N( ■if^t’lC y\t . X ' fl V X (’:. 2 ii'f imI lyfoxhxj ' ^ v -:-£0 i£ still present at the end of this time. (b) I ron in clay .- Iron occurs in two forms in clay, depending; on burning conditions. Ferrous iron forms in the presence % of carbon v;ith no excess air, while ferric iron results from excess 1 air . (c) Critical period in burning .- Up to 110° "water of plasticity" is driven off. The v/ater left in the clay coming from the dryer is usually called "hygroscopic water" . From 110° to 500 or 600° the clay substance breaks up and the "chemical water" is driven off . The clay is nov; at a dull red heat and if air is circulating the carbon starts to burn. The rate of burning increas- es with increase in temperature. The carbon near the surface burns first, leaving a dark core in the center. As the air attacks the carbon in the interior of the brick, the passages between the grains of clav become choked v;ith CO or CO and C 0 which must dif- 2 ^ fuse outv/ard before fresh air can enter and burn the carbon. This process requires time, since the diffusion of gases through small capillaries is a. slow process. Between 900 and 1000° the pores start to close up, so the passage of e,ir is restricted. It, is absolutely necessary to have complete oxidation before this contra, ct- ion has progressed to any great extent. At 1000° the ferrous iron fuses in contact with the clay, and so if oxidation is not complete a.nd the ferrous iron is not oxidized to ferric iron at this point, we have formed a slag v/hich slows up oxidation due to the increasing difficult^'' of air entering into the interior. In bad cases the bubbles entangled wath the fusing slag cause the brick to swell and bloat.^ •I. ^ if ♦rf'il p ij| :«b-" I JrV- ,*:r y . t4 <-»r ' • • 1 >■ .«>‘i'' ^ f^.-'^C ■ 4 i»ii ■'’i rwcXf'’^ i*i'*i p V » * ‘ ■■ ' _ ’"p'm ,■’’ 0tn:x\ t Vl ifJ ■ . «h , I I •>- . *i ifi/ * - *y--- ^ ur^ T 4 «i 10 ‘ .: /’Tfl \».*J ■ sr, r * ilQ ..-.tf Jt’.ii ■ •',;.# i?> I • . ^ ^ J§^' '*' '^ ^«o's 4 vii” , ^~'j "f i». ’ ’ /-r !f 3 >*iw.. "id OC'C ^ lr«r- . j **vV y .»•>' v.- ♦ ■ * * .. . - <• ^ , : p/o 5 » * .»i ivrc-uxp^l r^lilp ud t.\' ..: S'.:- ..V ”A^i*> , *ii i»r r ;f!(* .r»c)*fj5t .- 9 T iXL-lf. r t^. V-i ■ ; t : V .; ; V t '. • - . , X i n ^ *lli \';tiir- .' « r/r*' JW^0' , i ^1 -A A i •: w'.‘"-!^ *v- ■ « .I-*.'v^ e»V^ui,^Qi .(jI^^ ,^A I .• ■<* «• * 4 K-^,:tr't n.i: » ■> : X.*<^p> ■'‘■vi^smf X‘€,t»«v' '1^:^ t*a nXr X ^ .- 11 ^ 1 * f , A O** A ■ m I II* JBJBi' 4 ?i![>tstj^*~' ^1 (d) Stepjn » » The state of the atmosphere circulating v/hi ch around the brick during oxidation determines the rate at^fresh air penetrates the interior of the vra.re . The more air the better, as brick in badly ventilated parts of the kiln are more apt to have cores. The effect of steam in the kiln is to act as a screen preventing the entrance of air, so it is necessary to remove all steam as quickly as possible. II SXPERIT.CETTTAI. (a) Determination of the carbon content of the clay .-. The clay used in this v/ork V7as obtained from the Coates’ Manufactur- ing CorTipany, Fort Dodge, Iowa, and v;as a blaclf shale used in the making of brick and tile. The carbon content was determined by 4 the " Scott Wet Process” , using the apparatus shown in Fig.Fo.l. One gram of the clay was mixed with 10 grams K^Cr 0 ^ 2 7 PS an cxidizer in flask A. 50 cc. cf H SO v/as admitted 2 4 through B and then boiled for five minutes. Before adding the H SO , the system was cleaned out by drawing air through the train 2 4 for five minutes, and then v/eighing U tubes C and D, After oxidation wa.s complete the tv/o U tubes were v^eighed again. The in« crease in v/eight showed the amount of CO absorbed b^^ the Ma Ca. This amount multiplied by .2727 gave the amount of carb on^ v/hich divided by the amount of clay used a,nd multiplied by 100 gave the percentage. Three preliminary tests were run and then three complete tests, giving 3.93, 3.S and 9^ of carbon. ; 5 , *, MMiniBiK. -5- (b) Principle of the method .- To carry on the study of the coinhustion of organic materials in clay, it v/a.s desired to find the amount of CO given off during oxidation. To accomplish this 2 it was necessary to find some way of measuring this gas. Our first attempt v;as with the use of gas mete-rs. e volume of gas and air v/as measured by one meter, the gas then passing through a CO 2 absorption tra.in and then through a second meter. The difference in the two meter readings would give us the CO content of the 2 gas. This process was not successful due to the fact that the hydrocarbons in the gas tended to interfere v;ith the accuracy of the meters. The apparatus finally adopted is shown in Pig. No. 2. (c) Aonaratus and method .- The furnace used v/as made of a 4” porcelain tube and covered with an asbestos coverii-ig. It was wound Y/ith No. 20 chromel wire, connected in series with an ammeter and a rheostat used to vai’y the current. The outer end of the furnace v/as closed with a perforated disk, softer the sample was in place. At the other end a porcelain tube connected with a conden- ser and drip bottle to collect the moisture from the gasses. The drying of the gases were completed by passino- through a H .SO wash 2 4 bottle. The CO,, v/as absorbed by passing through a solution of KOH made by dissolving 300 grams cf KOH in 300 grams of v/ater. The gases a;nd air then passed through another drying tube containing H SO which collected all v/ater given up by the KOK solution. 2 4 This absorption train v/as placed on a balance pa.n so the am.ount of CO absorbed could be weighed. The draft through the furnace was obtained by means of i -7- a vacuum pump run by a smalTi motor. A manometer which had been calibrated by means of a ga.s meter was attached to the train. By reading* the manometer, the volume of air passing through the fur- nace was known. (d) Procedure .- The cube of clay was placed in the center of the furnace with a thermocouple beside it. Pieces of brick were placed in front of the cube so as to divert the in- coming air to all parts of the brick. The suction pump was started so as to produce a draft of 2 cubic feet of air per minute through the furnace. This draft was kept constant through all the experiments. The air would burn the carbon to CO^ and pass through the H SO bottle into the KOH solution where the CO was absorbed. 2 4 2 ' These bottles were placed on a balance so the amount of CO 2 absorbed in the KOH solution could be weighed at a given time. The temperature was kept constant for each run. Several tests were made at each temperature and the results checked. The results obtained are shown graphically in Pig. Ho. 3. The points for a given run are indicated by the use of the same color. ( e) The use of M nQ^ as an oxidizing agent .- It v/as desired to know what effect MnO v/ould exert unon the oxidation of 2 the clay. With this idea in view some of the clay was ground to pass through a 20 mesh screen and cubes of clay were made mixing 1, 3, 5, 3 and 10"'^ of 5ln0^ v;ith the clay. The clay was pressed in a 2" X 2” X 2” mould and burned in a muffle kiln. Draw trials were drawn at 500, 600, 700, 800 and 900 degrees. Ho decrease in the size of the cores could be seen, except in the ones containing 10!^ 76 ^m5 CO^ Q>VOlve.d. -9- MnO • This decrease could be seen for each trial dra?/n, showing 2 that MnO acted as an oxidizer at all temperatures at \7hich trials 2 were drawn and with the same effect at all these temperatures. Ill RESULTS (a) Discussion of results .- The results obtained are rather v/hat one would expect from preceding knowledge of the oxidation process. The slight difference in the data for differ- ent runs at the same temperature is due to the difference in texture of the samples. The curves shov/ the marked increase in the rate of oxidation for each increase in the temperature. is interest- ing to note the slight increase in the rate of oxidation with the addition of lInO . It would be interesting to find the increase 2 in the rate of oxidation at a constant temperature, with varying volumes of air. The time available was not sufficient to take up this side of the problem. ("b) Summary . - The results of the investigation are shown on Dig. ho. 3.