URBANA el ILLINOIS STATE GEOLOGICAL. SURVEY 3 3051 00005 6410 Digitized by the Internet Archive in 2012 with funding from University of Illinois Urbana-Champaign http://archive.org/details/briquettingillin55737pier STATE OF ILLINOIS HENRY HORNER, Governor DEPARTMENT OF REGISTRATION AND EDUCATION DIVISION OF THE STATE GEOLOGICAL SURVEY M. M. LEIGHTON, Chief REPORT OF INVESTIGATIONS — NO. 3 7 BRIQUETTING ILLINOIS COALS WITHOUT A BINDER BY IMPACT Second Report of a Laboratory Investigation BY R. J. PIERSOL ^ PRINTED BY AUTHORITY OF THE STATE OF ILLINOIS URBANA, ILLINOIS 1935 STATE OF ILLINOIS Hon. Henry Horneb, Governor DEPARTMENT OF REGISTRATION AND EDUCATION Hon. John J. Hai.i.iiian, Director SPRINGFIELD BOARD OF NATURAL RESOURCES AND CONSERVATION Hon. John J. Haixihan, 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., Biology Henry C. Cowles, Ph.D., D. Sc, Forestry Arthur Cutis Willard, D. Engr., LL.D., President of the University of Illinois STATE GEOLOGICAL SURVEY DIVISION URBANA M. M. Leighton, Ph. D., Chief Geological Resource Section Coal Division Oil and Gas Division Non-Fuels Division Areal and Engineering Geology Division Subsurface Geology Division Division of Stratigraphy and Paleontology 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 cgpl^T (48241) Contents PAGE Chapter I — Introduction 7 Previous work 7 Suggested lines for present investigation 7 Determination of effect of varying quantities of mineral matter on briquets produced by impact process 7 Determination of exact limits of controlling variables 8 Determination of physical and chemical causes of compaction 8 Studies of the effect of time and exposure upon the briquets 8 Burning characteristics of the briquet 8 Systematic tests of a variety of coals 8 Tests upon fine coals and coal dusts 9 Future investigations 9 Protection by patent application 9 Acknowledgments 10 Chapter II — Summary of the Impact Investigation 11 Summary of previous results 11 Summary of present findings 11 Operating range . 12 Effect of variations in the percentage of mineral matter 13 Effect of variations in the character of the coal 13 Comparison of briquets made from coals of different geographic locations and from different stratigraphic horizons 13 Weathering characteristics 13 Burning characteristics 14 General conclusions 14 Energy consumption in commercial scale production 14 Chapter III— Coals tested 17 Chapten IV — Heating equipment and procedure 21 Description of rotary oven 21 Procedure with rotary oven 22 Impact die temperature 24 Chapter V — Operating range 27 Coals investigated 27 Results of tests 27 Washington County coal 27 Impact pressure range 27 Temperature range 30 Range of time of preheating 34 T3J PAGE Frank li n County coal .'i a) -3 ■ — t* 03 0) 3 o £• ft »»« O PS o a o o o oo o o — O o c O O o o t 1 - < coo o op -T — CO -r -T -T rr 1 - CO o • -* 1 1 - 01 01 3 1 - 00 W, C i / i - 99 rH / / IT. 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CO 6 IO ph en O «. o o >, v CO rt a 3 >h o £- O § ft M 3 A O > c3 1-1 § Ph Ph 0> .£ GO. + o « CH (1) O 0, CO s "3 w> >> ,Q ri <1> O M 1-1 -: 01 OJ M m C -r -* {£) — t" M CO CO 1 f 3 71 r. / V O 1 - - ■-- — i-l CM •* C* -T - f CICIX i— I tN "T O co -r rHCO-f C 1 CC -T •-H cc -r ^H CO -H ffl 3 CO CI "OCO O- T* CO CO co -f /: :' O CO CI CO T-i 1-i CO -*' r-l -H i-H r-H ci co 1— 1 r* "5 go co co CO CI 'O co co io co i> CO o co co oc -t- CI i-H C5 -t >o co os co — CO 1 - Ifl M -f -f o CO — t 1 -f >o -t 'O -H -fi •r 'o M o *H CO i-H C5 -# -# o ci >o 1- 1^ co »o co ci "o *j OC -f i-H CO CO CO -ti © -r 1- l~ CO ci i- CO •* co co co ■* CO -t 1 co co CO -+ co co ^s CO i-H CO -* co i^ i-i o O CO 1-CO "O iO ,c CS i-h CO o i-H CI 'O CO l^'cO CO l^i io' CO o CO -V TH T— I "" rt rt 1—i i i-H CM CO -— ? i rt i-h ci co i—i ci co i-h CI CO ^ CI CO i-h ci co t3 d e o P"43 O i CO CO CI CO •& -f CO s « _>> - CO CO co co co co Dal of late anal sis 03 OS OS OS o o C2 ""' " " ~ "~ H i-H m CO f lO Num- ber ample; ana- U'zed I-H m to -,-. CO CO -* HH g_.giS.-t> u? -Q g O « £ a ° r en '-^ o T—fl lO 03 co o © CD >i CO CO CO LO C3 CD ^X i- 1 o s ° 6 6 «j m^j m o co -V CO 1 — 1 CO f -3.S el 3 TD b- LQ CO CI co CI CI CD w "o 3 + o , — s O ,£, s ^_^ + 'c? _C + 'c? 2- + '5 3- a a 'aj o a a o + -a 13 o o bO w 14 IH _c 3 H o o 1 1 2 .2 -3 o •3 o t-t -* tf o o > > £ t§ & & i= CHAPTER IV HEATING EQUIPMENT AND PROCEDURE DESCRIPTION OF ROTARY OVEN THE equipment used and the procedure followed in this series of investigations are the same as those of the earlier tests except that a rotary type of oven instead of the stationary oven 1 was employed for preheating the coal. The rotary -oven provided greater uniformity of temperature in the coal, a desirable improvement in this series of tests in which operating conditions were to be exactly determined. ooooooooooooooooooo ooooooooooooooooooo Fig. 1. — Rotary oven for heating coal. The rotary oven (Pig. 1) consists of one of the previously used compaction dies surrounded by a heating coil and is herein referred to as the oven. The coal is heated in a cell constructed from a 3%-inch length of 2-inch pipe. The outer end of the cell is supported by the transite bushing B, loosely fitted into the open end of the oven. The inner end of the cell is closed by a removable plug which is loosely fitted into the socket C. in the closed end of the oven. The plug may 'Op. cit, p. 32. [21] 22 BBIQUETTING ILLINOIS COALS WITHOUT BINDEB be removed by a spanner wrench filled into the holes at J). The outer end of the cell is closed by a permanent steel plate insert, through which there is a 3-inch length of i/|-inch steel pipe through which the thermometer may be inserted into the cell and through which also moisture and other gases from the coal obtain outlet. The cell may be rotated by the wooden handle E. PROCEDURE WITH ROTARY OVEN Heat is applied to the oven containing the empty heating cell un- til the desired temperature is reached. The cell is then withdrawn from the oven, the plug removed, a weighed quantity of coal inserted, O 300 x xxx x x x> X o°° o 'Sose®*®* 85 i o S ! « ? y <, ? « s i « y o O - CELL X = OVEN 10 20 30 40 50 TIME OF HEATING (MINUTES) Fia. 2. — Heating curve for coal in rotary oven. the plug replaced and the cell put back into the oven as soon as possible (about 30 seconds). The coal is preheated for the specified length of time, the cell being periodically rotated by hand, three-fourths of a revolution every 30 seconds. The rate of increase of temperature of 45-grams of coal, rotated in the oven first heated to 300 °C, is shown in figure 2. The circles represent the temperature readings of the coal and the crosses those of the oven which was maintained at temperatures less than 300° C, by regulating the heating current. The data for this curve are shown in Table 3. For duplicate samples of coal, the results were reproducible. heating equipment and procedure Table 3 — Heating op Coal in Rotary Oven (Data for Fig. 2) 23 Temperature, degrees C. Time of heating (minutes) Oven Coal 1 265 289 293 293 293 291 291 195 2. . 210 3 223 4.. 239 5.. 246 6.. 255 7 263 8 290 289 268 9 273 10 290 278 11 290 290 281 12 284 13 290 286 14 290 287 15 290 289 16 290 290 17 290 291 18 290 292 19 290 292 20 290 293 25 290 294 30 290 295 35 290 295 40 291 291 291 293 295 45 296 50 296 55 296 60 293 293 293 293 293 293 297 65 298 70 298 75 298 80 299 85 299 Using a temperature-heating current graph (Fig. 3, Table 4) pre- pared from data obtained under equilibrium conditions, the temperature of the heating cell is readily regulated. The circles (Fig. 3) represent the temperature readings of the heating cell and the crosses those of the surrounding oven. The rate of increase of temperature of 45 grams of coal rotated in the oven at a temperature of 300 °C. (Fig. 2) is such that the coal in the heating cell attains the temperature of the oven about 15 min- utes after its insertion. The rate of temperature increase differs among coals from different sources and among samples of the same coal hav- ing different moisture content. 24 BRIQTJETTING ILLINOIS COALS WITHOUT HINDI. I! After attaining the temperature of the oven, the temperature of the coal increases slightly above thai of the oven, evidently due to an exo- thermic reaction of the coal. 350 n X 300 ( I > t 8 < ! 250 9 \ s ! 200 9 j t > ) : 150 I X 100 o = CELL X = OVEN 50 12 3 4 5 HEATING CURRENT (AMPERES) Fig. 3. — Heating curve for rotary oven. IMPACT DIE TEMPERATURE The preheated coal is transferred rapidly to the impact die which has the same temperature as the coal, as determined by means of a thermocouple inserted in a hole between the heating coil and the inside wall of the die. The temperatures within the die, in the space in which the coal is placed, were found by repeated trial to be within 3°C. of those of the die wall, the temperature of the wall and the opening in the die being measured alternately by the same thermocouple (Table 5). HEATING EQUIPMENT AND PROCEDURE 25 Table 4 — Heating of Rotary Oven (Data for Fig. 3) Heating current (amperes) Temperature degrees C. Cell Oven 2.5 150 182 207 225 246 266 286 320 351 146 3.0 177 3.5 4 203 222 4.5 244 5.0 263 5.5 283 6.0 316 6.5. . 332 Table 5 — Temperature Distribution in Impact Die Time (minutes) Temperature °C. Side opening Center of die 305 2 308 4 304 6 307 8 303 10 304 12 303 14 306 16 303 18 305 20 302 r 22 304 . 24 302 26 305 28 302 CHAPTER V OPERATING RANGE EARLIER tests demonstrated that satisfactory briquets could be formed without binder only by impact, hence it was desirable to ex- amine somewhat more fully than was previously possible the effect of variations in the impact pressure, the temperature of the coal, and the time of preheating. Such considerations as size of the coal and size of the die seemed of less critical importance than matters of operating control once it had been demonstrated that strong briquets could be made of commercially practical size from coal of a size easily obtainable. COALS INVESTIGATED Having discovered in the earlier investigation that the Illinois coals behaved somewhat differently under the impact process, it was desir- able in carrying on systematic tests on operating range to distinguish between coals briquetting with ease and those less readily briquetted. No. 6 coal from a Washington County mine was selected as a repre- sentative of the class of easily briquetted coals and No. 6 coal from a Franklin County mine was selected as representative of the class of more refractory coals. 1 Coals from each of these mines were used In the preliminary tests 2 so that considerable information is now available in regard to their behavior in the briquetting process. RESULTS OF TESTS WASHINGTON COUNTY COAL Impact pressure range. — Variations in the height of drop of a 500-pound hammer in the Turner impact machine produced the various impact pressures used. Only two sizes of hammer were available and the lighter 250-pound hammer did not produce strong briquets even at the maximum possible drop of six feet. Eighteen cylindrical briquets, 1.5 inches in diameter and approxi- mately 1.2 inches in height, were compacted from 40 grams of coal pre- a Op. cit, Table 5, p. 46. 2 Op. cit., Chapter III. [27] 28 BBIQUETTING ILLINOIS COALS WITHOUT BINDER heated LO minutes in the rotary oven al a coa] temperature of 250°C. The comparative strength of these briquets, classified according to height of drop, is shown in Fig. 4 and Table 6, which indicate a satis- factory impact pressure range of the height of drop of a 500-pound * 3 O 2 O O o o o o 12 3 4 5 HEIGHT OF DROP (FEET) Fig. 4. — Range of impact pressures used in briquetting Washington County coal and per cent tumbling loss of the briquets. hammer from 2l/ 2 to 5 feet, with an optimum value at 4y 2 feet. This is in agreement with the value of impact pressure previously recom- mended. Briquets formed by a 2 1 / 2 and 3-foot drop show a higher tumbling loss than those from other heights investigated. OPERATING RANGE 29 Table 6 — Impact Pressure (Height op Drop) Range Washington County Coal (Data for Fig. 4) Tumbling loss (per cent) Height of drop (feet) Individual Average 2.5 4.9 4.9 3.0 3.5 4.0 4.5' 4.8 4.5J 2.0' 6.0 2.6 3.5 3.3 2.0, 2.41 2.0 > 4.65 3.2 2.3 4.5 2.4 J 2.31 2.0 2.0 5.0 i.7j 2.61 3.0 J 2.8 :j(i BRIQUETTING [LLINOIS COALS WITHOUT BINDER In order that results obtained by the rotary oven might be cor- rectly evaluated in comparison with results obtained previously with the stationary oven, the samples were about evenly divided and were run half in each type of oven, other conditions being similar, in all eases impaction was by a 4%-foot drop of a 500-pound hammer. The temperatures recorded (Fig. 5 and Table 7) refer to the oven tempera- ture in the case of the stationary oven and to the coal temperature (heating cell temperature) in the case of the rotary oven. o z j 6 X . : o X ) O = STATIONARY OVEN X = ROTARY OVEN X X O ( > X * X ) X * X 25 50 100 150 200 250 300 350 TEMPERATURE (DEGREES C) Fig. 5. — Range of temperatures at which Washington County coal was preheated and per cent tumbling loss of the briquets. Temperature range. — Investigations of the effect of preheating coals 10 minutes at temperatures varying from 125° to 350°C. were made, using 48 samples of Washington County coal. The tests were made at intervals of approximately 25 °C. and two or three samples were tested at each temperature. The results showed that average tumbling OPERATING RANGE 31 losses of 3 per cent or less characterized only those briquets heated between 185° and 300°C. inclusive (Fig. 5 and Table 7), thus giving a wide range of permissible temperatures. Table 7 — Temperature Range Washington County Coal (Data for Fig. 5) Rotary Oven Stationary Oven Tumbling loss (per cent) Temp. °C. Tumbling loss (per cent) Temp. °C. Individual Average Individual Average 350 8.01 18.8/ 3.6 2.61 4.9/ 2.61 2.6/ 1.71 2.0 2.0 J 2.31 2.0 1-7 J 2.01 1.7 2.0 J 2.31 3.6/ 2.61 4.0/ 5.51 4.3/ 25.81 4.3/ 13.4 3.6 3.8 2.6 1.9 2.0 1.9 3.0 3.3 4.9 15.0 350 11.31 18.4 17.4 J 2.31 (a) 12.0 17. Oj 2.41 2.0 \ 2.4 J 2.01 2.3 \ 3.0 J 2.61 2.3 \ 3.6 J 3.01 2.9 \ 3.0 J 2.31 2.3 \ (a) 7.6 J 15.31 12.7/ 100.0 15.7 322 310 288 325 300 275 250 225 10.4 274 245 221 2.3 2.4 2.8 3 185 162 153 125 200 175 150 4.1 14.0 100.0 (a) Wide range of tumbling loss evidently due to nearness to critical point of briquettlng. 32 BRIQUETTING ILLINOIS COALS WITHOUT BINDEB lii anticipation of this parallel series of tests, an investigation had been made to determine the relation between the temperature of the coal in the heating cell of the rotary oven at the end of 10 minutes and the oven temperature (Table .S). 'Phis investigation revealed a difference in temperature of about 25°C. The assumption was accordingly made that a similar difference existed between the oven temperature and the coal heated in the stationary oven. Hence, since the temperatures for the stationary oven are measured as oven temperatures and those of the rotary oven as coal temperatures, for comparative purposes the circles in Fig. 5 should he shifted about 25°C to the left (toward lower temperature). It is evident that results obtained by the use of the rotary oven are similar to those obtained using the stationary oven, except that coal heated in the rotary oven produced slightly better briquets through a slightly wider temperature range (25°C). OPERATING RANGE 33 Table 8 — Temperature Lag Washington County Coal Temp, of coal preheated 10 minutes ( C C.) Temp, of rotary oven (°C.) Individual Average Individual Average 3501 350/ 322 3101 310/ 2891 287/ 2741 274 272 J 2461 243 \ 247 J 2221 220 220 J 1861 185/ 1651 162/ 1551 152/ 1261 125/ 350 322 310 288 273 245 221 185.5 163.5 153.5 125.5 3751 373/ 330 3281 323/ 3111 306/ 2931 293 293 J 2611 267 266 J 243] 242 243 J 215 \ 210/ 1971 204/ 1771 173/ 154 \ 151/ 374 330 325.5 308.5 293 265 243 212.5 200.5 175 152.5 34 BBIQUETTING ILLINOIS COALS WITIIOI "I' BIN DEB Range of time of preheating. — In this scries of tests the primarj variable was the period of preheating extending from 5 minutes to 2 hours. The impact was produced throughout by the fall of a 500- pound hammer 41^ feet, and the temperature of the rotary oven was o o o o 5 o ° o Q 20 4 60 80 100 120 PREHEATING T LME (MINUTES) Fig. 6. — Relation between preheating time of Washington County coal and tumbling loss of the briquets. maintained at 250°C, the optimum temperature suggested by the series of temperature range tests. The actual temperature of the coal in the heating cell at the end of the various periods of preheating (Fig. 6 and Table 9) ranged from 185° to 249 °C, these temperatures being within the permissible range (Fig. 5) but for the most part below the optimum temperature previously determined. OPERATING RANGE 35 Table 9 — Time of Preheating Range (a) Washington County Coal (Data for Fig. 6) Time of preheating Temp. °C. of coal at end of heating- Tumbling loss (per cent) (minutes) Individual Average Individual Average 5 200 185 192.5 2.8 2.8 2.8 10 230 235 232.5 2.3 2.3 2.3 15 232 228 230 2.0 2.2 2.1 20..... 234 232 233 3.0 2.5 2.8 30.... 247 242 244.5 2.5 2.3 2.4 45 249 247 248 2.3 2.3 2.3 60 248 247 247.5 3.4 3.4 3.4 90 244 244 6.4 6.4 120 249 249 8.7 8.7 (a) Temperature of impact die kept a.t 250° C. The results of tumbling tests on the briquets (Fig. 6) indicate a desirable range of time of preheating of from 5 to 50 minutes, a much wider range of permissible temperature than was previously known. 36 ISR1QUETTING I I.I.I NOIS COALS WITHOU'J HINDI B FRANKLIN COUNTY COAL Impact pressure range. — In the determinations of the impact pres- sure range of a Franklin County coal similar conditions were maintained as were u^d in testing the Washington County coal. o o ° o 12 3 4 5 6 HEIGHT OF DROP (FEET) Fig. 7. — Range of impact pressure used in briquetting Franklin County coal and per cent tumbling loss of briquets. Higher impact pressures (Fig. 7 and Table 10) were necessary to procure strong briquets, a drop of 31/2 to 5y 2 feet being necessary with an optimum at 5 feet, as compared with 41/2 feet for Washington County coal, and briquets so formed showed a slightly greater tumbling loss than the Washington County briquets. The tumbling losses in- crease very rapidly with drops of 4 feet and less. OPERATING RANGE 37 Table 10 — Impact Pbessuke Range Franklin County Coal (Data for Fig. 7) Tumbling loss (per cent) Height of drop (feet) Individual Average 3.5 4.0 4.5 5.0 5.5 5.31 7.9/ 5.6 \ 8.4/ 2.8] 4.5 [ 2.8 3.7 j 2.81 3.1/ 3.7 \ 2.9/ 6.6 7.0 3.4 3.0 3.3 ::x RBIQUKTTING ILLINOIS COALS WITHOUT I'.IMiKIl Temperature range. — Since somewhal better briquets were pro- duced from Washington County coal heated in the rotary oven than [rom coal heated in the stationary oven, temperature-range investigations with Franklin County coal were made exclusively with (lie rotary oven. z o o o O ° O O o o 100 150 200 250 300 350 400 TEMPERATURE (DEGREES C) Fig. 8. — Range of temperatures at which Franklin County coal was preheated and per cent tumbling loss of the briquets. The best briquets (tumbling loss about 3 per cent) (Fig. 8 and Table 11) were formed from Franklin County coal at a preheating tem- perature range from 175° to 350 °C, Avith briquets of approximately equal strength throughout. This range is about the same as that of Washington County coal (175° to 325°C.) but the strength of the Franklin County briquet is less influenced by temperature. OPERATING EANGE 39 Table 11 — Temperature Range Franklin County Coal (Data for Fig. 8) Temp, of coal preheated 10 minutes (°C.) Temp, of rotary oven (°C. Tumbling loss (per cent) Individual 370 \ 375/ 350 345 323 \ 318/ 3001 292/ 2801 280/ 257 \ 258/ 220 220 223 220 1901 191/ 1701 172/ 1501 150/ 130 130 Average Individual 372 347 321 296 280 257 220 190 171 150 130 3801 392/ 370 365 339 335 320 310 3081 303/ 275 273 250 250 250 250 2251 225/ 2081 208/ 180 180 1501 147/ Average Individual 386 367 337 315 306 274 250 225 208 180 148 21.2 3^6 2.9 3.6 3.2/ 3.2/ 3.1 3.7 3.1/ 2.8/ 3.4 3.4 2.8' 4.5 2.8 3.7 2.8 3.6 4.3 2.8 9.0 6.4 52.0\ 31.4/ Average (a) 3.3 3.2 3.4 3.0 3.4 3.4 3.2 3.6 6.7 41.7 (a) Anomalous results may occur at either end of operating range. 40 BRIQUET'J I M. IIMils COALS WITIIOI T KIMJKK Range of time of preheating. — Following the same procedure used in testing Washington Couniy coal, the eoal tempera! lire ai the end of various periods was first noted (Tabic 12) and the quality of the briquet resulting from imparl determined by tumbling (Fig. 9). The results indicate thai the si rouges! bri<|iieis (tumbling loss between '.'> and 4 per cent) were formed after five and ten minutes of preheating °3 22 o o o o o 20 40 60 SO 100 PREHEATING TIME (MINUTES) Fig. 9. — Relation between preheating time of Frank- lin County coal and tumbling loss of the briquets. and others less strong (tumbling loss 4.5 to 5.6) after heating from 20 to 50 minutes. A closely similar range (5 to 50 minutes) was ob- served for Washington County coal but the tumbling losses of the Franklin County briquets, particularly those made from coal preheated 20 to 45 minutes, were greater than those of briquets made from Wash- ington County Coal. OPERATING RANGE 41 Table 12 — Time of Preheating Range Franklin County Coal (Data for Fig. 9) Temp, of preheated coal Tumbling loss (per cent) Time of preheating (°C.) (minutes) Individual Average Individual Average 5 2101 210/ 210 3.41 4.0/ 3.7 10 220] 223 220 220 J 221 2.8) 4.5 2.8 3.7 J 3.4 20 (a) 245 245 5.6 5.6 30 (a) 255 255 4.8 4.8 45 2481 250/ 249 4.51 4.7/ 4.6 60 2601 247/ 253 15.5) 19.2/ 17.4 90 2851 260/ (b) 272 14.21 33.0/ 23.6 (a) Due to mechanical difficulties, duplicates were of no value. (b) Temperature got out of control. CHAPTER VI EFFECT OF VARIATIONS IN THE PERCENTAGE OF MINERAL MATTER IN considering effects of variations in the mineral content upon the briquetting characteristics of coal, it was considered advisable to limit the investigation to coals which yield less than 21 per cent ash. The actual mineral matter content will in all cases exceed the ash con- tent, the amount of excess varying with the amount and kind of mineral matter. However, since an arbitrary limit of 20 per cent ash is in excess of the ash content permissible in coals used in the manufacture of satis- factory briquets, if such high-ash coal produces briquets of satisfactory strength, the amount of ash above that limit is of little or no importance so far as its effect upon the strength of briquets is concerned. Similarly if satisfactory briquets can be made of coals up to 20 per cent ash con- tent, irrespective of the kind of mineral matter, it is apparent that the kind of mineral matter is of little or no importance. In view of this, tests were made to determine the effect upon the briquetting characteristics of increasing the ash content of a low-ash coal by regular increments until about 20 per cent ash content was at- tained. These tests indicated that ash up to 20 per cent of the coal did not weaken the briquets appreciably. This being the case there was no reason for examining the effect of variations in the relative pro- portion of the various minerals present. PREPARATION OF SAMPLES Using the sample of Washington County coal from which other tests were made, the sample for low-ash content was prepared from hand- picked 3 by 6-inch lump, referred to as Washington County (B). This was crushed to minus 4-mesh. The minus 48-mesh coal was discarded because of difficulty in handling the fine sizes in gravity separation. The final sample contained 7.2 per cent ash and 8.5 per cent moisture, the air-dried moisture being 2.9 per cent. 143] 44 BBIQUETTING [LLINOIS COALS WITHOUT BIN DEB The high-ash sample was prepared from a grab sample of minus 2-inch coal. This was crushed to minus t-mesh 3 from which the minus 48-mesh was discarded. The — 4 -+- 18 mesh coal was separated into two fractions at 1.10 specific gravity and the 0.oa1 fraction discarded. The sink fraction contained 19.6 per ceni ash and 1.7 per cenl moisture after the evaporation of the gravity separation liquid. After subjection lo standard air drying procedure the coal contained l.(i per cent mois- ture. COMPOUNDING OF SAMPLES Samples of coal having intermediate ash content of 10, 12.5, 15, and 17.5 per cent were prepared by compounding the two end samples. The minus 48-mesh of the low-ash samples had been discarded, as stated, because it was necessary to discard the fine size coal of the sam- ple of high-ash coal prepared by gravity separation. z u a. ujIO O 5 z _l m 5 5 10 lb 20 2 5 ASH (PER CENT) Fig. 10. — Influence of mineral matter on mechanical strength of briquets as measured by tumbling loss. Coal used was from Washington County. 0_ ° \ o c EXPERIMENTAL RESULTS Variations in the ash content of the coal up to nearly 20 per cent ash did not produce appreciable weakening of the briquets (Fig. 10. Table 13). EFFECT OF VARIATIONS OF MINERAL MATTER 45 Table 13 — Influence of Mineral Matter Washington County Coal (Data for Fig. 10) Tumbling, loss (per cent) Ash (per cent) Individual Average 7.2 10.0 3.3) 2.6/ 4.9) 5.2/ 3.41 4.1/ 3.11 4.0/ 2.41 3.6/ 2.81 4.0/ 3.0 5.1 12.5 15.0 3.3 3.6 17.5 19.6 3.0 3.4 CHAPTER VII EFFECT OF VARIATIONS IN THE CHARACTER OF THE COAL IN this chapter is described the results of tests on coal samples consisting of pure banded ingredients, separated from hand-picked blocks of coal, and of the ingredients mixed in various proportions. The artificial blending of ingredients produces a range of variation probably in excess of the natural range of variation in the proportion of ingred- ients due to variation in coal type. Results of additional tests on coals of the various ranks represented in the main Illinois coal basin are also included. INFLUENCE OF THE BANDED INGREDIENTS Clarain, the bright laminated coal, is the principal banded ingred- ient of Illinois coals and generally composes more than 50 per cent of the bed. The remainder of the coal is usually composed of the brilliant jet-black vitrain with relatively unimportant fusain or mineral char- coal. Splint coal (durain) is occasionally present in thin layers but is unimportant. The proportions of these ingredients vary considerably in the same bed and from seam to seam, nor are they similarly distrib- uted in the bed and in the various prepared sizes of coal. Hence in- formation in regard to the effect of variations in the relative propor- tions of the ingredients is of interest. Preparation of samples. — The only coal ingredients investigated were clarain, vitrain, and fusain. No tests were made on splint coal because of its relative unimportance in Illinois coals. The samples of clarain and vitrain were hand-picked from LaSalle (No. 2) coal and are referred to as Woodford County (A) and Woodford County (B) respectively. The samples collected at the mine were more carefully worked over in the laboratory until an essentially pure sample of each ingredient was obtained. The sample of fusain was obtained from a local concentration of the material in No. 6 coal in St. Clair County. The material used consisted of soft unmineralized fusain. [47] 48 BRIQTJETTING ILLINOIS COALS WITHOUT BINDEB S o Q ■< o O o CO CD CO fa si .2 »- CO co CD -H l~ l^ .*-. CD c3 -t^ OS CM i-H t~~ ©cm' rs c^j co ■* co co O c? t> S coo coo O'* co co'-* © i-i -*' CD o -H W l-H CM "6 << c3~" Hon HIMOJ HMCO « 3 3| -d o | -v co M< CO CO CO 03 >> en C2 © c3 c3 p>s tn cd CO © CO -* CM i— 1 >> o t^ co CD "3^ 3 6 6 6 fc d 3 CD CD m = 3 h cD°9 ,ai ■Sg'clc. O 3 O cci S " o '3 '5 N 2S§ « ? i T<»_ ,0.3 EFFECT OF VARIATIONS IN COAL CHARACTER 49 The sample of each ingredient was passed through rolls and screened to minus 4-mesh. The material was quartered down and samples taken for analysis (Table 14) by the Analytical Division. Method of testing. — Individual samples for briquetting consisted of the pure ingredients and various combinations of the ingredients, (a) clarain and vitrain, (b) clarain and fusain, and (c) vitrain and fusain. Operating conditions for all tests approximated optimum values. A 40-gram sample was preheated 10 minutes at 250°C. in the rotary oven, transferred to the die heated to the same temperature, and then im- pacted by a 4l/2-foot drop of the 500-pound hammer. Experimental results. — As in previous tests the tumbling loss is the basis for evaluating the briquet (Figs. 11, 12, 13, and Tables 15, 16, 17, respectively). The varying percentages of each of two components are plotted on the abscissae, one component decreasing along the upper abscissa and the other increasing along the lower abscissa. Clarain-vitrain ratio. — The mechanical strength of the briquet remains unchanged, within experimental limits, up to at least 25 per cent vitrain (Fig. 11). When vitrain approaches 50 per cent or is present in greater quantity than 50 per cent, the strength decreases. Clarain-fusain ratio. — Tests on briquets made from fusain showed that briquets could not be made from this material when pure, nor from clarain containing more than 25 per cent fusain. Of these samples of mixtures of clarain and fusain (Fig. 12) in proportions of 5, 10, and 25 per cent fusain respectively, only that with 5 per cent fusain yielded fairly strong briquets (tumbling loss 4 per cent). Vitrain-fusain ratio. — Percentages of fusain up to about 5 per cent materially improve the strength of a vitrain briquet (Fig. 13), but higher percentages cause a very rapid decrease in strength. Percen- tages of fusain higher than 10 per cent produce a briquet weaker than that made from pure vitrain. Fifty per cent fusain causes utter failure of the briquet. BRIQUETTING 11,1.1 Mils COALS WITHOUT ItlNDKIt 30 O 20 CLARAIN (PER CENT} 00 75 50 25 A } O ° < C I 25 50 75 100 VITRAIN (PER CENT) Fig. 11. — Tumbling loss of briquets formed from mixtures of clarain and vitrain. CLARAIN (PER CENT) 100 75 50 25 ^40 H Z LU o a. UJ a. 30 \^> m i/> O _i ^ 20 z _j OQ 2 H 10 ( < > o o 25 50 75 100 FUSAIN (PER CENT) Fig. 12. — Tumbling loss of briquets formed from mixtures of clarain and fusain. EFFECT OF VARIATIONS IN COAL CHARACTER 51 Table 15 — Clahain-Vitrain Ratio (Data for Fig. 11) Tumbling loss (per cent) Clarain (per cent) Vitrain (per cent) Individual Average 100 2.51 2.6/ 2.5 95 5 1.91 2.2/ 2.1 90 10 3.0) 2.2/ 2.6 75 25 2.21 2.3/ 2.3 50 50 2.81 5.2/ 4.0 100 (a) 21.01 2.6/ (a) Wide range of tumbling loss evidently due to nearness of critical point of briquetting. Table 16 — Clarain-Fusain Ratio (Data for Fig. 12) Tumbling loss (per cent) Clarain (per cent) Fusain (per cent) Individual Average 100 2.5) 2.6/ 2.5 95 5 3.31 5.1/ 4.2 90 10 9.71 19.0/ 14.3 75 25 30.01 64.0/ 47.0 52 BRIQUETTING ILLINOIS COALS WITHOUT BINDER Effect of various proportions of banded ingredients. — The in- vestigations in briquetting characteristics of the banded ingredients in general indicated thai the natural proportions in which these materials occur in coal arc more favorable lor the formation of good briquets than any blend which greatly increases (lie percentage of either villain or fusain. Clarain makes as good briquets as Hie whole coal, probably be- 100 70 VITRAIN (PER CENT) 75 50 25 O t| O 25 50 75 100 FUSAIN (per cent) Fig. 13. — Tumbling loss of briquets formed from mixtures of vitrain and fusain. cause its physical constitution closely approximates that of the whole coal and in clarain the ingredients are intimately blended. Since the varia- tions in type of Illinois coals are in general of a small order, being due to only small variations in the proportions of the ingredients, it is im- probable that in any coal either fusain or vitrain occur in sufficient amount to be of much importance in their effect on the briquetting EFFECT OF VARIATIONS IN COAL CHARACTER 53 characteristics of the coal. It is quite possible, however, that in small sizes of prepared coal, concentration of one or the other of these ingredi- ents may take place to the detriment of briquetting strength. Table 17 — Vitrain-Fusain Ratio (Data for Fig. 13) Tumbling loss (per cent) Vitrain (per cent) Fusain (per cent) Individual Average 100 (a) 21.0\ 2.6/ 97.5 2.5 3.6\ 3.6/ 3.6 95 5 4.31 6.0/ 5.2 92.5 7.5 14.71 19.2/ 16.9 90 10 24.01 (a) 4.8/ 75 25 (a) 100. 04 62.0/ 50 50 GO- (a) Wide range of tumbling loss evidently due to nearness of critical point of briquetting. (b) No briquet formed. Table 18 — Analyses op Coals op Various Rank Lab. No. C-683 C-684 C-697 C-750 C-696 RANK (Unit coal B.t.u. 14,200 14,400 14,600 14,800 15,000 Location Countv Macoupin Randolph (A) . . Williamson (A) . Saline (A) Saline (A) Bed Analyses (a) Moisture 12.7 10.4 8.5 5.5 6.3 Ash 7.7 11.1 8.2 8.2 7.5 (a) Moisture and ash are recorded on "as received" basis. 54 HKKjlJICTTINU ILLINOIS COALS WITHOUT BINDER EFFECT OF VARIATIONS IN RANK OF COAL The moist mineral matter-free B. t. u. value has recently been adopted by the American Standards Association as the tentative basis for defining the rank of coals such as are found in Illinois. This value corresponds to what might be termed moist "unit" coal, and for Illinois coals varies from about 11,200 to 14,200; figures which correspond approximately to 14,100 and 15,100 on the unit coal basis. In order to study the effect on the strength of briquets of variations in rank of the coal from which they were made, five coals were selected representing successive increments of approximately 600 units in heat value (200 units on a "dry" or unit coal basis). The samples (Table 18) were hand picked from clean lump coal to obtain as clean coal as possible. o 9 T o 14200 14400 14600 14800 RANK (UNIT COAL B. T. U.) 15 200 Fig. 14. — Influence of rank of coal on mechanical strength of briquet as measured by tumbling loss. Preparation and briquetting of samples. — All samples were crushed to minus 4-mesh and briquetted under standard conditions. Experimental results. — There appears to be a slight but consistent decrease in the strength of a briquet with increase in the rank of the coal (Fig. 14 and Table 19). EFFECT OF VARIATIONS IN COAL CHARACTER 55 Table 19 — Influence of Rank of Coal (Data for Fig. 14) Unit coal B.t.u. Tumbling loss (per cent) Individual Average 14200 ±100 14400 =■= 100 1.81 2.0/ 3.41 3.7/ 4.31 4.1/ 5.0\ 4.3/ 5.51 5.6/ 1.9 3.6 14600 * 100 14800 * 100 4.2 4.6 15000 * 100 5.5 CHAPTER VIII COMPARISON OF BRIQUETS FROM DIFFERENT COALS FOR the purpose of investigating in a preliminary way varieties of commercially important coals produced in Illinois, 25-pound grab samples of %-inch screenings were collected in 19 mines located in various parts of the coal basin and from each of the workable beds. The coals represent practically the complete range of variation in rank and type, and the results obtained are believed to represent fairly the varia- tions in the briquetting characteristics that may be expected among Illinois coals. Analyses of the samples collected were made by the Analytical Division (Table 20). Table 20 — Analyses of %-Inch Screenings Lab. No. County Bed Moisture (a) Ash (a) C-685 C-666 C-742 C-688 C-633 C-687 C-700 C-637 C-632 C-634 C-686 C-665 C-698 C-638 C-667 C-669 C-699 C-620 C-635 Bureau Edgar Franklin (C) . . Fulton Grundy Henry Jackson Livingston .... Menard (A) . . . Menard (B) . . . Peoria Randolph (B). Saline (C) . . . . Sangamon (B) . Vermilion (A) . Vermilion (B) . Williamson (B) Woodford (D) . Woodford (E) . 7 18.7 21.2 5 12.4 18.2 6 10.3 12.3 5 14.7 21.7 7 18.8 11.4 1 14.6 20.8 6 9.5 18.2 7 15.0 15.6 5 16.2 13.6 14.7 14.6 5 15.0 19.7 6 11.2 24.2 8.8 14.5 5 14.2 15.9 7 13.1 19.5 6 20.1 11.6 6 8.8 13.2 2 12.8 24.1 2 13.7 16.1 (a) Moisture and ash are recorded on an "as received" basis. PROCEDURE OF TESTS Briquets were made from each sample under a consistent set of conditions. These consisted of one impact of a 500-pound hammer, dropped from a height of 41/2 feet on a 45-gram sample of coal that had [57] 58 BBIQUETTING ILLINOIS COALS without BINDER been preheated For aboul lo minutes in an external rotary oven to a temperature of 250°('. find transferred to the impact die (also heated to 250°C). The standard tumbling test was used as a practical and applicable criterion of that kind of mechanical strength desired in a briquet. RESULTS The results of the tests showing the strength of briquets, and also the bed moisture of the coal and the briquetting loss, have been tabulated with respect to geographic locality of the mine from which the samples were taken and the stratigraphic position of the coal bed. Effect of geographic position. — Southern Illinois coals are some- what more difficult to briquet than coals from other parts of the State (Table 21). There is no consistent difference in briquetting capacity among the coals mined elsewhere than in Jackson, Franklin, Saline, and Williamson counties, for briquets of varying mechanical strength were produced from coals in each district. Effect of stratigraphic position. — The results of the briquetting tests (Table 22) when arranged with respect to the stratigraphic posi- tion of the coals fail to show definite superiority or deficiency in strength in the case of any bed. The samples of each bed, with the ex- ception of No. 1 coal, cover a wide geographic area in which the geologic conditions affecting the coals have considerable variation. briquets from different coals Table 21 — Effect of Geographic Location 59 Geographic location Mine Bed Tumbling loss (per cent) Individual Average Northern Illinois Bureau 7 5.6\ 6.8/ 6.2 Grundy 7 5.71 ■ 7.2/ 6.5 Woodford (D) 2 6.71 7.6/ 7.2 Woodford (E) 2 3.11 3.5/ 3.3 Western Illinois Fulton 5 3.51 5.1/ 4.3 Henry 1 6.01 8.8/ 7.4 Peoria 5 10.01 6.5/ 8.3 Central Illinois. . . Menard (A) 5 5.11 6.2/ 5.7 Menard (B) 5 3.81 1.5/. 2.7 Sangamon 5 2.31 3.1/ 2.7 Southwestern Illinois. . . Randolph (B) 6 4.31 5.3/ 4.8 Eastern Illinois Edgar 5 8.61 7.3/ 7.9 Livingston 7 2.51 3.5/ 3.0 Vermilion (A) 7 6.61 7.7/ 7.2 Vermilion (B) 6 3.31 3.3/ 3.3 Southern Illinois Saline (C) 5 7.81 9.8/ 8.8 Williamson (B) 6 8.51 8.5/ S.5 Jackson 6 5.0\ 7.2/ 6.1 Franklin (C) 6 8.31 9.2/ 8.8 fiO briquetting illinois coals without binder Table 22 Effect of Rtratighaphic Position Bed Mine (county) Tumbling loss (per cent) Individual A verage 1 Henry 0.0 1 8.8/ 7 4 2 Woodford (D) (J 7 7.6/ 7.2 Woodford (E) 3.11 3.5/ 3.3 5 Edgar 8.61 7.3/ 7.9 Fulton ' 3.5) 5.1/ 4.3 Livingston 2.51 3.5/ 3.0 Menard (A) 5.11 6.2/ 5.7 Menard (B) 3.81 1.5/ 2.7 Peoria 10.01 6.5/ 8.3 Saline (C) 7.81 9.8/ 8.8 Sangamon (B) 2.3 \ 3.1/ 2.7 6 Franklin (C) 8.3\ 9.2/ 8.8 Jackson 5.01 7.2/ 6.1 Randolph (B) 4.31 5.3/ 4.8 Vermilion (B) 3.31 3.3/ 3.3 Williamson (B) 8.5 \ 8.5/ 8.5 7 Bureau 5.61 6.8/ 6.2 Grundv 5.7) 7.2/ 6.5 Vermilion (A) 6.6) 7.7/ 7.2 CHAPTER IX WEATHERING CHARACTERISTICS THE two following chapters concern the results of tests on certain properties of briquets which would affect their desirability both actually and as compared with coal. These properties are: (a) the weathering characteristics of the impacted briquets, and (b) the ignition and quenching temperatures. WEATHERING TESTS The study of weathering characteristics of impacted briquets con- sisted in determinations of (a) the effect upon the briquets of standard accelerated weathering tests used in testing coal and (b) the effect upon calorific value of the briquets and possible disintegration effect of con- tinuous outside exposure. Accelerated weathering tests. — The accelerated weathering tests applied to the briquets followed the procedure recommended by the U. S. Bureau of Mines for determining the weathering characteristics of coal/ which is briefly as follows : "1. Not less than three and preferably five samples of fresh coal should be taken from the mine representing different locations. "2. The samples to consist of 30-50 lumps of approximately l^-inch cubes. These cubes should be placed in a sample can and the voids around the cubes filled with fine coal to prevent abrasion and oxidation of the cubes in transit to the laboratory. "3. On receipt at the laboratory, screen out the fine coal used for packing by placing the coal on a ^-inch screen. The fine material simply drops through the screen without the necessity of shaking. "4. Discard any pieces that show evidence of being cracked or crushed. Weigh and determine air drying loss in a standard oven at 30° to 35 °C. for 24 hours. "5. Remove the sample from the oven, weigh and immerse in water for one hour. "6. The coal is drained and dried again in the oven at 30° to 35 °C. for 24 hours. "7. Remove the sample from the oven and place the coal on a standard ^-inch square mesh sieve. The sieve is shaken gently so that fine coal particles will drop through. The sieve should not be shaken vigorously enough to break any of the cubes. 1 Fieldner A. C, Selvig, W. A., and Frederic, W. H., Accelerated laboratory test for determination of slacking characteristics of coal : U. S. Bureau of Mines, Rept. of Inv. 3055 (1930). T61J 62 BRIQUETTING ILLINOIS COALS WITHOUT lilMil.lt "X. Weigh the oversize and undersi/.e and calculate I he percentage of undersize. "9. This constitutes the first cycle. Repeat the alternating wetting and drying until 8 cycles have been completed in the case of coals thai do not slack readily. The cumulative percentage of the fines produced at each cycle is taken as an index of the slacking characteristics of the coal." In general Illinois coals show less than 5 per cent degradation at the end of the first cycle, whereas coals of lower rank (sub-bituminous) show 5 per cent of degradation and more, usually considerably more. Phocedure. — Briquets given the accelerated weathering tests repre- sented Will County (B), Sangamon County (A), and Franklin County (B) .coals, the coals having the composition shown in Table 23 as de- termined by the Analytical Division. Tests were carried through 8 cycles. Kesults. — The results of the tests showed no disintegration for the briquets made from any of the coals tested. The same briquets were sub- jected to an additional eight cycles, making a total of 16 cycles. Slack- ing losses were as follows: Will County, 0.16 per cent; Sangamon County, 0.11 per cent; and Franklin County, 0.12 per cent. The briquet's relative, resistance to these accelerated weathering tests as compared to coal is suggested by Table 24, which shows the re- sults obtained by Mitchell 4 on a variety of Illinois coals through a series of 8 cycles. Table 23 — Analyses of Coal Used in Briquets foe Accelerated Slacking Tests Lab. No. Mine (county) Moisture (a) Ash (a) C-690 C-689 C-743 Sangamon (A) Will (B) Franklin (B) . . 12.7 16.9 8.7 9.2 3.4 10.0 (a) "As received." 4 Mitchell, D. R., Accelerated slacking tests of some Illinois coals : Acad. Science, 23rd Annual Meeting, Vol. 23, No. 3, March, 1931. Trans. 111. WEATHERING CHARACTERISTICS 63 Table 24 — Accelerated Slacking Tests by Mitchell (a) Accumulative percentage weight loss Cycle Will County coal Franklin County coal 1 1.1 5.2 7.6 12.6 19.1 21.9 25.4 29.5 0.5 2 1.4 3 2.9 4 6.4 5 8.8 6. . 9.4 7 10.5 8 11.5 (a) Trans. Illinois State Acad. Sci., A^ol. 23, No. 3 (March) 1931. Outside exposure tests. — The purpose of these tests was to ascer- tain the effect of weathering on the amount of disintegration and the change of calorific value of the impacted briquets. Procedure. — The briquets tested were made under standard condi- tions from Will County (A), Washington County (A), and Franklin County (A) tipple samples of lump coal. Three briquets from each county were placed in separate compart- ments of a wooden tray, each briquet being entirely exposed. The tray was placed on the exposed flat roof of the Survey laboratory for a period of 90 days from February 24 to May 25, 1934. The exposure (Table 25) included 6 snow falls, totaling 19.4 inches, each followed by thaws, average ranges in daily temperature of 22°F. (in 22 instances across the freezing temperature), a maximum daily range of 36 °F. and a total range of 101°F., with relative humidity ranging from 100 to 30.3 per cent. 64 BIQUETTING ILLINOIS COALS WITHOUT LIMH.lt Tahll 2") Wlatiilk Record Feb. 24 to May 25, 1934 U. S. Weather Bureau, Urbana, Illinois Station Precipitation °F. Temperature Relative humidity Day Snow (in.) Total (water) (in.) Max. Min. Cloudy or fair 1934 February 24 1.1 3.6 0.4 .11 .36 .04 17 17 17 14 31 41 43 46 54 47 38 35 32 25 19 28 51 66 49 50 57 69 33 36 53 61 39 32 37 43 39 33 40 58 66 58 64 69 76 69 68 65 60 67 73 69 64 4 10 4 10 1 20 34 34 38 37 32 26 22 16 4 5 19 40 25 30 34 33 16 11 27 39 22 19 26 22 33 21 15 32 41 30 32 42 54 46 47 47 38 43 49 51 38 91 . 3 96.7 87.0 88.0 88.0 77.7 97.7 97.7 68.3 55 . 3 57.7 100.0 72.7 88.3 77.0 72.3 72.3 61.3 62.3 65.0 55.0 81.3 81.3 82.0 72.0 60.7 86.3 77.0 70.0 63.7 98.3 83.0 81.0 61.7 57.0 80.3 84.0 65.0 76.3 86.7 86.7 88.7 63.0 65.7 62.3 62.1 76.3 c 25 26. . c F 27 F 28 F March 1 F 2 .27 .01 .05 .02 C 3 C 4 C 5 c 6 c 7 2.8 .31 c 8 c 9 1.2 .12 c 10 F 11 F 12 F 13 C 14 .03 F 15 C 16 F 17 .23 .78 C 18 4.3 C 19 F 20 F 21 F 22 0.4 0.8 .04 .08 C 23 24 C F 25 F 26 1.05 .61 C 27 28 4.8 c F 29 F 30 C 31 C April 1 .20 C 2 F 3 C 4 .03 C 5 c 6 .13 c 7 F 8 F 9 F 10 C 11 .08 c WEATHERING CHAKAI TElilSTK'S 65 Table 25 — Concluded Day Precipitation °F. Temperature Relative humidity Snow (in.) Total (water) (in.) Max. Min. Cloudy or fair 1934 12 48 45 61 57 60 67 74 68 49 50 65 75 58 56 58 52 60 72 73 73 78 81 82 78 84 82 82 90 83 74 71 74 64 70 76 85 88 88 88 91 84 79 74 68 34 29 34 45 38 43 53 45 40 30 41 40 37 32 42 33 32 39 46 47 55 55 58 60 55 63 54 59 62 52 43 58 53 50 42 50 55 60 64 67 60 49 53 37 47.7 56.0 56.0 71.0 64.7 54.0 46.0 43.3 54.7 59.3 49.0 43.0 51.7 44.7 92.7 53.3 52.0 49.3 55.7 59.3 50.0 47.3 54.0 84.0 64.0 30.3 45.0 44.0 31.3 41.0 43.3 76.3 78.0 43.7 44.7 43.0 34.3 52.3 46.0 88.3 51.3 31.0 65.0 35.3 F 13 . C 14. . F 15 .03 .33 c 16 . F 17 F 18 F 19 F 20 c 21 c 22 .01 F 23 c 24 F 25 F 26 .22 c 27 c 28 F 29 F 30 F May 1 F 2 c 3. .. , c 4 F 5 c 6 F 7 F 8 c 9 c 10 c 11 F 12 c 13 .27 c 14 c 15 c 16 F 17 F 18 F 19 F 20 F 21 c 22 .12 F 23 F 24 .14 c 25 F i;i; HKiQurcrriNU Illinois coals WITHOUT BINDEB Results. -Excep! for a slight surface cracking, the briquets have the same appearance as freshly made briquets. Some chemical change look place during the exposure of these sets of briquets as shown by the analyses of the composite samples (Table 26). There was a decrease in unit H.t.u. value of from 1.01 to 1.01 per cent, variable; increases in moisture, the amount apparently increas- ing with the rank of the coal, and a decrease in volatile matter, the amount apparently decreasing with the rank of the coal. Differences in ash and sulfur content are probably due to the slight changes in the weight of the briquets due to the variation in moisture and volatile mat- ter, although there is some possibility of oxidation of pyrite. Table 26 — Analyses of Briquets Used in Outdoor Exposure Tests County Will Washington Franklin Lab. No. C-738 C-833 C-739 C-834 C-740 C-835 Bed 2 6 6 "A" "B" "A" "B" "A" "B" Moisture Ash Volatile 1.2 5.2 46.3 3.6 14205 3.8 5.0 44.8 3.3 14012 1.6 11.1 45.3 3.3 14288 4.2 10.9 43.2 3.4 14139 1.6 7.0 38.6 1.2 14380 6.2 6.S 38.1 Sulfur B.t.u. (unit coal) 1.2 14149 Analyses "A" and "B" are for briquets before and after exposure, respectively. CHAPTER X IGNITION AND QUENCHING TEMPERATURES THE ignition and quenching characteristics of fuel are two characteristics possible of determination on a laboratory scale using but a small quantity of fuel. Tests to determine these characteristics could be applied to the impacted briquets supplied by the laboratory equip- ment, whereas large scale burning tests must be reserved until briquets may be available in quantity through the operation of an experimental or pilot plant. The significance of the ignition and quenching temperatures lies in their usefulness as an index of ease of lighting and of sustaining ignition. Ignition temperature is an important factor determining the suitability of coal for storage and bunkering. The fact that the compo- sition of the impacted briquets differs from the coal from which they are made mainly in containing less moisture suggested the probability that ignition and quenching temperatures would, for this reason, be at least slightly less than those characteristic of the coal. The results of the tests indicate that this is the case. DEFINITIONS AND METHODS There is no standardized method for the determination of ignition temperature. Arms 1 has summarized the various suggested ignition temperatures as follows: (1) The temperature at which self-heating begins. (2) The temperature to which coal must be raised in order that it may unite with oxygen and burn. (3) The temperature (zone) at which rapid self -heating begins. (4) The temperature to which coal must be raised in order that it may maintain its own combustion. (5) Definitions on a time basis, such as' the time required for a given external temperature to ignite the coal or cause it to glow. (6) The temperature of the glow point. •Arms, R. W., The ignition temperature of coal: Univ. of 111. Eng\ Exp. Sta. Bull. 128 (1922). [67] 68 BBIQl ETTING MI.INOIS COALS WITHOUT BINDER (?) The blue flame temperature. (8) The crossing point of the outside heat, coal-heat curves. (Wheeler.) Anns round that none of these definitions was entirely satisfactory. In addition, all these methods require coal of very fine size. In the present study it is desired to compare the ignition tempera- tures of impacted briquets with those of corresponding natural coals. All samples should be in lump Form so that the effect of iextural differ- ences may he observed. Preliminary tests indicated that satisfactory results may he ob- tained for lumps of coal (or briquet) under constant conditions of rate of heating and air supply using the appearance of a yellow flame as an indicator of ignition temperature. In this report the definition of ignition temperature selected is the temperature at which the yellow flame appears, since this is readily re- producible for identical samples. Quenching temperature, for the purposes of this investigation, is defined as the temperature at which the flame from burning coal will disappear as the temperature is lowered. It is evident that the minimum temperature of sustained combustion approaches this quenching temper- ature, the interval diminishing with increasing precision in operation. Thus the quenching temperature is a limiting value of maintenance temperature. EQUIPMENT The equipment and procedure of the present series of tests were devised to test the quenching and ignition temperatures of impacted briquets and the coal similar to that from which the briquets were made. No comparison is made with results obtained on Illinois coals by earlier investigators of ignition temperature, since the purpose was simply to inquire into the relative behavior of the two kinds of fuel under similar conditions of operation. An electric muffle furnace (Fig. 15) was constructed for use in the ignition and maintenance temperature tests. The furnace consisted of a 3-inch inside diameter alundum tube A, 18 inches long, wound with 2 heating elements B, each having a resistance of 15 ohms, of No. 19 chromel wire. Each coil had a separate controlling resistance C, and an ammeter D, in series with it, so that the temperature of the front and rear part of the furnace could be controlled separately, if desired. The alundum tube with the heating coils was given a coating of alundum cement about I/4 inch thick, fired, and then placed in a steel and transite case E, 8 inches square and 30 inches long, packed with sil-o-cel ; a IGNITION AND QUENCHING TEMPERATURE 69 steel tube F, 214 inches inside diameter and 26 inches long, was fitted into the alundum muffle;, to protect it, and to increase the heat capacity of the furnace and thereby minimize small fluctuations in temperature. Fig. 15. — Diagram of combustion furnace. A steel tray G, 1% inches wide, and 30 inches long, was used to carry the nickel dish H, on which the sample I was placed. The thermocouple J was mounted in the tray with its junction directly under the dish. The thermocouple leads extended out to a milli-ammeter, mounted near the open end of the furnace. Air was introduced into the furnace through a small iron pipe K, leading to the back of the furnace, being located beneath the tray; thus the air was heated to fur- nace temperature before its escape from the pipe. The air supply was measured by a calibrated orifice and differential manometer. The fumes exhausted from the furnace were collected by the hood L, and vented outside the building by the fan M. PROCEDURE For the determination of ignition and quenching temperatures, samples were prepared from briquets and from blocks of the correspond- ing coal by cutting them into cubes weighing approximately 3 grams each. 70 BRIQUETTING [LLINOI8 COALS WITHOUT BIN DEB Before performing duplicate tests, the approximate ignition temper- ature of the particular sample was obtained by exploratory trial. Then the temperature of the rear half of the furnace was set 15 degrees higher than this approximate temperature. Tins was to assure a slow rate of temperature rise of the sample through its ignition temperature. At the instant a yellow flame appeared, the temperature of the sample as measured by the thermocouple was recorded as ignition temperature. The quenching temperature was obtained by drawing the tray sup- porting the flaming sample (for which the ignition temperature had just been determined) into the cooler front half of the furnace, thereby causing the flame to be quenched. By means of exploratory tests, this lower temperature was set slightly below quenching temperature, thereby assuring a slow rate of temperature drop of the sample through its quenching temperature. At the instant the yellow flame disappeared, the temperature of the sample as measured by the thermocouple was recorded as quenching temperature. EFFECT OF AIR SUPPLY Since the air supply undoubtedly has an important bearing on ignition and quenching temperatures, standardization of conditions .of air admission was necessary and a series of tests was run for this purpose. Briquets, four months old, from AVashington County coal, were used in this standardization. Table 27 shows both the ignition and quenching temperature values for an air supply ranging from 2 to 6 cubic feet per minute. Series (a) represents tests, made from pieces of the same briquet, showing the effect of various rates of air flow. Series (&), (c), (d), and (e) are duplicate tests of briquets formed from the same coal under identical conditions. The average values of both igni- tion temperature and quenching temperature are not affected by wide variations of air flow within the middle of the range investigated and therefore the median value of 4 cubic feet per minute was selected for use in all tests. BRIQUETS COMPARED WITH NATURAL COALS The briquets for these tests were prepared from coals from four counties, Will, Sangamon, Washington, and Franklin, with analyses as shown in Table 28. From samples of lump coal similar to those used for the briquets, pieces were selected for corresponding tests. The coals at the time the briquets and tests were made had been in the laboratory about four months. ignition and quenching temperature Table 27 — Effect of Air Supply 71 Test Air (cubic feet per minute") 2.4 3.0 3.5 4.5 5.0 5.4 Ignition Temperature (a).. (&).. (c) . . . (d).. «... Mean (a).. (6).. «.. (d).:. «... Mean 544 509 549 549 549 554 578 549 549 554 544 554 558 554 551 563 529 558 529 558 549 563 558 549 563 558 551 558 554 549 554 545 550 557 547 553 Quenching Temperature 480 509 494 470 509 539 578 519 534 485 534 529 558 499 485 563 - 509 549 529 558 509 534 534 509 558 504 . 549 509 544 544 541 519 514 512 526 534 544 549 549 549 549 548 519 539 534 534 524 530 Table 28 — Analyses of Samples Used in Determination of Ignition and Quenching Temperatures Lab. No. C-418 C-690 C-614 C-743 County Will (A) Sangamon (A) Washington (B) Franklin (B) Bed Moisture (a) . . Ash (a) Volatile (b) Sulfur (b) B.t.u. (unit coal) No. 2 9.1 4.7 50.4 3.4 14517 No. 5 12.7 9.2 46.6 5.0 14517 No. 6 8.5 7.2 49.2 5.0 14448 No. 6 8.7 10.0 40.0 1.1 14672 (a) (b) "As received" basis. Moisture-free and ash-free basis. Ignition temperature.. — -For each coal investigated (Table 29) data show a consistently lower ignition temperature due to briquetting. Only for Sangamon County coal is the amount of decrease so slight as to be comparable with the magnitude of mean deviation. Quenching temperature. — Although from its very nature the ex- perimental determination of quenching temperature is less accurate than that for ignition temperature, nevertheless the mean values (Table 30) show the same general lower values for briquets compared with the corresponding coals. 72 BBIQUETTING ILLINOIS COALS WITHOUT BINDER ►J «! o O IS p rH « pq H K P En o W iO >fl tc u: 4H CD 'rH pq P CI CO ^ 1 1 1 ,-H JQ i-H ++++ ! + 1 1 to o C. -f -t< C5 OS O O O -* n-t?i"OHC.OH iQ 'O >o U3 'O lO -t< -t 1 'O a o g tn "o3 O a > CD Q oococaconoizio ++! +1 l+l EG 42 O io "o -t >o -h -v >o -v m lO »0 »Q lo »0 lO »0 »0 t-O CD 3 .2" pq > P H-tOOOCHHO 1+1++Y i i 03 o -HOO-*^*0-*-*>0 cococ)-+-t<.-Hcococ-o lO iQiOiOi^ »0 iO"OiO C o e o3 C 03 "o3 O o CD P ^++1 ! 17+ cfi O ^fOOCJOC^-HClCO Cl--Hr-HOOOO.-Hr-H lO »0 'O "-O i-O ^O tH to +3 cd a" 'rH pq > CD P CN 1 T-H I I ,_| 1 CM T-H ++I M 1 ++ CO -a O OOTtoiOiTfOTforj CI C. ~ C. ~ O CO 3 Is "3 o O CD P T-HCO-tfl^T-H^POOT-H^fl ++ 1 1 + 1 ++ CQ O lONONiOO CI 'O "tf t^ N N CD N N 00 1^ t— '-H pq CD P OOrllcOcDHiOHN 1 + 1 •++ 1 1 + 42 O CDhhhhhcOOiO t^ t> CC > CD 1 1 1 17+++ "3 O o A 1 3] *+ "^ "+ 1 — + 1 tF "^f ^H "^ 1 — O o >o LO ,^ a. O0>00»0000*0 c3 CD Q r-H lO t— ! rH i— 1 CO CO (M t-l 0) 3 ++++ 1 1 1 .2* lOTfLOlOOlOOCOLO ffl o OOCOOO(X)ONCOCON TjtiO^#-*>tf-*^t<'*** > CD Q LO>-<^HTt<-#-*^OLO 13 o O COl-lf-llT-Hl-ll-llT-l 1 1 1 + +++ + 3] L0 00-+^f^#-*00 O COOOOCOCOCOCMCM P. i* LO LO LO lo io lo lo lo tsjo _g OOCOOCICOHN TO CD .ST CD Q T +l ++T ++ ^ '£ • O^C^^^Cl-^ClOO m O CT> CM O CO CO OMhh TjH IO 'O tO LO ^h LO LO LO s>° CD LO O iO LO LO O OS o o 'S' "3 o o +++I+TT O-^OOO^LO-*-* o >-H i-H C C". ■ C C-' »oo c o 1Q LO LO TjH LO -f T^ lO LO S 03 > CD Q coooocs^moooo bo + + l 1 1 I++ CO CD .2" 'fcH OOC>l!M(MNClCJH m o NShhhhONcD LO-*"#-#-*^t CD Q iO O LO >o -* O O CO -* 1 1 1 1 ++++ "3 o o NONNCDrHWLOO) o rtiHOlNro'^CONN 'c? '*-*COCO-*-*'*-*'* 5 CD O^CDCCO ^ CD .2" CD P 7 _|_ J_01 Ol —i ++ ! + t^ cm r- r- .-* co FQ o OO HONCOO CO tH "* CO TH ■* p d, a CD H p c3 CD a -C c ~ a b OrC < 74 BBIQTJETTING ILLINOIS COAXS WITHOUT BINDER Effect of moisture. — The lower ignition and quenching tempera- tures of the briquets as compared with the corresponding coal- are prob- ably due to the lower moisture contenl of the former. Coal when dried to a "moisture-free" condition has lower ignition and quenching temper- atures than coal from which the moisture has not been expelled (Table 31). Table 31 — Influence of Moisture on Ignition and Quenching Temperature (Tests on Washington County Coal) Ignition temperature Quenching temperature Tests As received Moisture- free (a) As received Moisture- free (a) Obs. Dev. Obs. Dev. Obs. Dev. Obs. Dev. a 558 558 549 558 544 549 558 544 552 +6 +6 —3 +6 —8 —3 +6 —8 6 529 529 539 544 509 534 558 539 535 —6 —6 +4 + 11 —26 —1 +23 +4 9 485 509 509 524 534 534 534 529 520 —35 —11 —11 +4 + 14 + 14 +14 +9 14 524 519 534 534 460 519 549 460 512 + 12 b +7 c +22 d . +22 e —52 f +7 g +37 h —52 Mean 24 (a) Not briquetted. BIBLIOGRAPHY 75 BIBLIOGRAPHY A bibliography of literature relating to briquetting bituminous coal without a binder is appended to Report of Investigations No. 31. Since the date of the previous publication the following literature has appeared: 1 — Holik, J., "Die bindemittelfreie Brikettierung nach Apfelbeck." Gluckauf 70, No. 17, 385 (1934). Description of a new type of roll press developed by Apfelbeck to briquet without binder lignite coal in Czechoslovakia and used on unit scale to briquet bituminous coals which, in certain instances, require the addition of a binder. 2 — Matsunami, H., and Morimasa, T., "Die Brikettierung von Kohle ohne Pechzusatz." Brennstoff-Ghemie l.'i, 471 (1933). Journal Fuel Soc. Japan, page 110 (1933). Description of laboratory tests in which bituminous coal is heated to the softening point and briquetted without binder in a hydraulic press at very low pressures. 3 — Thau, A., "Briquetting coal without a binder." Colliery Guardian lift, 333-335, 383-385 (1934). Summary of recent literature on briquetting coal without binder. 4 — Thau, A., "Steinkohlenbrikettierung ohne Bindemittel." Gluckauf 70, No. 16, 376-378 (1934). Description in English: "A new method of upgrading slack coal." Colliery Guardian U8, 352-353 (1934). Description of a process for partial carbonization of bituminous coal in which the coal at the softening temperature is compressed by being forced through an extrusion die. The compressed product may be broken up and screened into desired market sizes. X WASCHER'S" IBRARY BINDERS S07 S. Goodwin