Plastic Properties of Coking Coals JOSEPH D. DAVIS,F.
w. JUNG,BERNhRD JUETTNER,AND D. A. WALLACE
Pittsburgh Experiment Station, IT. S. Bureau of Mines, Pittsburgh, Pa.
I
pass 20 and remain on 40 mesh Plastic range tests hace b e m applied to twentyare used for the test. Temperas u r v e y of t h e g a s a n d two American coals covering the range in rank of ture of the charge and resistance coke making properties of those suitable for coke making; the results have are observed a t 2- to 5-minute A m e r i c a n coals ( 2 ) in which been correlated with coke making properties deterintervals within the plastic temthe Bureau of Mines has been mined on cokes made f r o m the coals under conperature range. When the mass e n g a g e d for the p a s t t h r e e first begins to become sticky, years, the plastic properties of stant carbonizing conditions by the Bureau qf resistance (to shear) develops t h e coals s t u d i e d h a v e been .Mines test method. The plastic range tests between the rabble arms and determined. Since in this study applied are: the Damm-Agde, for measuring the wall of t h e r e t o r t . The the gas and coke making properexpansion and contraction, the Layng-Hathorne amount of r e s i s t a n c e varies ties were measured by the same for measuring resistance to passage of nitrogen, within the plastic range with the uniform method, the opportunity kind of coking coal; for example, was p r e s e n t e d for finding the the plastometer for measuring m a x i m u m stickiwith some high-volatile coals the relation of plastic properties, as ness of the plastic mass, and the Marshall-Bird mass after initial fusion may bemeasured in the laboratory, to f o r measuring agglutinating power. The avercome very fluid, in which case carbonizing properties, particuage of the shatter index on 1.5 inches with the the resistance will drop almost larly to t h e q u a l i t y of t h e tumbler index on 1 inch is taken as a measure of to zero and then build up again coke. as decomposition p r o g r e s s e s . The methods used for deterthe quality of the coke. Apparent specific Finally, a sharp drop in resistmination of p l a s t i c properties gravity and cell space, at least for these twentyance indicates that t h e m a s s were taken from the literature two coals, are shown not to vary much for coals of (3) with very little n i o d i f i c a has set to form coke. medium and high rank. These properties are I n the Bureau of Mines extion. Three distinctly different not, therefore, considered a sensitive measure of pansion test a briquet of coal m e t h o d s w e r e u s e d in t h i s 1.9 cm. h i g h and 0.7 mm. in study of the p l a s t i c state of quality of cokes made f r o m different coals under diameter i s c o n t a i n e d i n an coal. They involve a measure of constant carbonizing conditions. 0.8-mm. Pyrex glass tube sunk the r e s i s t a n c e of the plastic i n a c o p p e r b l o c k w h i c h is coal to passage of n i t r o g e n , resistance of the mass to shear, and tendency of the mass to heated electrically at a uniform rate- over the plastic range. contract and expand during the plastic interval. Heating A plunger under a 500-gram weight rests on the briquet and conditions, particularly the heating rates, were kept close to its vertical position is read a t 2- to 5-minute intervals while those prevailing in the Bureau of Mines coke making test the test is in progress from a gage graduated in ten-thouin order that the results might apply as closely as possible sandths of an inch resting on its top. As the temperature rises, to those in the te-t. I n the nitrogen resistance test a 10-cm. there is first thermal expansion followed by a sharply defined column of sample sized through 20 and on 40 mesh is heated contraction, Around 400" C. expansion sets in and continues a t a uniform rate over the plastic temperature range in a until the mass sets. The welling coefficient is the ratio of Pyrex glass tube of 14-mm. bore. The sample consists of the length of the coked briquet to that of the briquet before four parts of sized electrode carbon and ten parts coal. being heated. The Sheffield Laboratory test, referred t o While the heating is in progress, nitrogen is displaced at a later, differs from the Bureau of Mines test in that the column constant rate through hot copper turnings (for removal of of coal is larger-1.6 cm. in diameter and 4 cm. high-the traces of oxygen) into the base of the heated tube by water scale is graduated in millimeters only, and the loading is under a head of 320 cm. Resistance to the passage of the 100 grams instead of 500. nitrogen through the sample is read a t 2- to %minute interSo far, twenty-two different coals covering practically the vals from a water manometer connected to the nitrogen entire range of rank of those used in America for production reservoir, and the temperature of the charge is read a t the of coke have been studied, and it is the purpose of this paper same time. From these data the temperatures, where re- to show the order of reproducibility attained in the plastic sistance develops and drops, are observed; by plotting the range tests, discuss the physical meaning of the test results resistance against the temperature over the whole range, and show how they are related to each other, and show what the maximum resistance and the temperature a t which it correlation has been obtained at this stage of the research occurs are obtained. with the coking properties of the coals as measured by the The plastometer is a cylindrical steel retort 13 cm. long shatter and tumbler tests standardized by the American and 4.8 cm. in internal diameter. It is rotated horizontally Society for Testing Materials. The relation of rank of the a t a constant rate in an electric furnace which is heated at the coals to shatter and tumbler indices, apparent specific grarity, rate of 3.4" C. per minute for the test. Through the tubular and porosity is also given. retort axle there is passed a shaft carrying rabble arms which REPRODUCIBILITY OF TESTRESULTS sweep the entire inner surface of the retort with a clearance of 0.8 mm. The external end of the shaft connects with a Table I shows the order of reproducibility attained in torsion head with graduated scale, resistance to turning being repeat tests (usually three) for eight coals of the series under taken up by a coil spring. The scale is calibrated in inch- study. The coals selected are: two medium high-volatile pounds directly with weights. Eight grams of coal sized to coking coals, one n-eakly coking coal, a coke-oven blend, one
iU COKKECTION with a
1269
I N D U S T R I A I, A N D E N G I N E E R I N G C H E M I S T R Y
1270
Vol. 23, No. 11
OF RESULTS, PLASTIC RANGE TESTS TABLE I. DUPLICATION
NITROGEN RESIST.4SCE hIETHOD (L.4ING-HATHORNE) PlasMax. AS TESTED resisttic range TEST ance c. .Mm.HzO % ..... 37.3 i 392-442 170 384-436 2 194 386-439 176 3
VOLATILE MATTER
COAL 22
COALBED Pittsburgh
I
.
.
-
20
-4verage Max. variation from av. Thick Freeport 36.3
21
Average Max. variation from a v . Green River 36.2
18 + 8
Average Max. variation from a v . 80% P r a t t 28.3 20% M a r y Lee
18
Average Max. variation from av. Pratt 31.5
8
Average Max. variation from av. M a r y Lee 27.6
15
Average Max. variation from av. No. 2 G a s 39.5
16
Average Max. variation from av. Alma 37.7
1 2
387-439 5 3 377-436 385-436
1 2 3
381-436 8 0 401-450 403-450 400-450
178 5 62 48 55
1 2
401-450 2 0 37 5-47 3 384-470
55 7 340 405
1 2 3
380-472 5 1 408-463 401-455 403-456
.....
389-441 4 1 (1) 393-445 (2) 393-443 (3) 394-
180 24 175 180
...
-
409 2
293 4 (1) 239 (2) 236 (3) 235
380 1 397 400 400
1.6 0 0.87 0.93 0.90
60
-
-
-
-
-
-
- 10
1 2 3
404-458 4 5 388-458 383-471 380-455
233 17 473 482 624
403-451 3 1 (1) 393-458 (2) 392-456
20.4 7.0 54.1 57.6
4 19 1 401 40 1
1 2 3 4
384-462 4 9 383-468 392-476 389-480 387-464
520 151 248 306 268 259
393-457 1 2 (1) 405-441 (2) 407(3) 4 0 5 4 3 8
55.9 1.8 6.5
.....
7:6
260 12 150 226 154
406-440 1 2
1 2 3
388-472 5 8 385-437 384-441 382-437
7.0 0.6 7.6
-
.....
-
.....
-
-
{;I
39j1445 (3) 396-445 (4) 399-448 (5) 393-451
..
..
317 1
392 1
2.5 0
150
301
384 3 383 376
1.8 0 3.6 3.6
83
379 4 378 378 380
3.6 0 1.1 1.1 1.1
260
...
-
... 401 0 413 416 415
... -
1
(1) 320 (2) 318
... 319 1
(1) . . (2) 2 8 i (3) 288
... -
... -
... -
... -
... -
288 1 (1) 265 (2) 269
379 1 369 375
1.1 0 2.1 2.0
10
4:7 6.5 7.4
415 2 434 433 436 437 436
110
-
-
... ... ... -
383-438 2 3 4.4 3.6
177 45 40.8
396-447 3 4 2.0 1.4
6.6 1.9 3.5
435 2 2.0
267 2 1.8
372 3 2.1
2.1 0.1 0.01
1.1 0 . 8
17.4
0.5 0.3
11.8
0.5
0.6
0.6
0.5
.....
-
-
c.
408 390 382 372 380 392 384
EXPANSION
% 60 50 60 70 260 150 80
... ... ... -
HEATING RATES Coffman and Layng ( I ) showed for the Layng-Hathorne test that varying the rate of heating from 1.5" C. per minute to as much as 9 " per minute had little influence on the TESTRESULTS AND
PRODUCED
~DAMM-AGD TEST-E Initial Initial contrac- expanTotal tion sion
..... . ... -
interval is readily reproducible. The maximum resistance to passage of nitrogen and the resistance to shear (plastometer) are not so easily reproducible. Maximum variation divided by number of tests contributing to average is less than 15 per cent in most cases, but in some the average variation is larger, I n these methods it would undoubtedly be better to make at least five separate tests and average the results. This procedure is followed in the agglutinating power test; the results (Figure 4) correlate better with the strength of the coke than those of the nitrogen resistance and plastometer methods (Figures 2 and 3).
COALS O N PLASTIC RANGE
c.
+
117
416 2 419 418
87.9 355 Davis 60% Ocean, 40% 87.0 321 Davis: 20% f Ocean, 80% 86.0 319 Ocean 85.4 297 M a r y Lee 87.1 319 P r a t t , 80%a 86.8a 317 Mary Lee,20% Pratt 86.8 301 0 Calculated from analyses of coals blended.
+
2.3 0 1.6 1.6 1.6
51.8 7.2 13.4 27.4
O
280 (3) 285
%
376 2 379 381 379
393-444 28.2 1 1 4.1 No plasticity
high-volatile coal regularly used alone for making coke, one lowvolatile strongly coking coal, and two high-volatile gas coals. The initial critical temperatures by any of the methods of test are reproduced fairly easily, the plastometer perhaps giving the most closely agreeing results, the Damm-Agde test next, and the nitrogen resistance method least. The temperature marking the highest point of the plastic rangethat is, the point of maximum plastic resistance-is most accurately measured by the plastometer, although this point is not always sharply defined in either case. With some coals the curve giving the relation between temperature and plastic resistance tends to waver over several degrees at its highest point, and this tendency appears more pronounced in the nitrogen resistance test. The amount of expansion found by the Damm-Agde test (this is free expansion) for a coal in going through the plastic
%
...
2.3 2.3 2.3
286 1 (1) 297 (2) . . . 131 290
3 85-46 3 1 0 (1) 405-450 (2) 400-451
__
COAL
c.
377 377 375
400 4 408 409 411
373 65 240 250 210
O F BLENDIXG OF TABLE 11. EFFECT
{:
...
37.2 2.2 32.3 27.4 25.1
414 417
Average Max. variation from av. Av. max. deviation, units Av. max. deviation, % of units measur e d
c.
EXPANSION
(DAMM-AGDE TEST) Initial SyellexpanIng, Swelling sion ratio
-
44.7 59.0
-
Initial contraction
-
(1) 386-463 (2) 384-463
.....
Davis
C O N T R A C T I O N .4ND
YPLASTOYETER hf ETHODPlasMax. Temp. of resist- max. retic ance sistance range c. Kg.-cm. C. 396 (1) 3881440 3j:3 403 (2) 393-441 35.0 396 (3) 388-442 39.4 403
LAYNG-RATHORNE TEBT Plastic Resistance range C. Mm. HzO 412-498 774 407-487 307 399-466 414 395447 263 384-461 520 380-472 373 404-458 233
O N THE PROPERTIES O F THE COKE
PLASTOVETER TEST Plastic Resistrange ance ' C. KO.-em. 411-427 29.7 395457 25.3 401-449 40.9 387-443 40.0 393-457 55.9 385-463 51.8 405-451 20.4
-
AGQLU- SHATTER APPAR TINATINQ
AND
ENT
TUMBLER SP. POWER I N D I C E S GR.
Kg.
Av. %
12.2 11.6 10.6 9.7 13.0 10.1 9.9
82.5 79.4 77.8 56.7 82.2 73.6 66.7
0.82 0.80 0.82 0.83 0.82
0:84
!'iovember,
1933
INDUSTRIAL AND ENGINEERIhG
temperature of softening of the coal but that it had considerable effect on the maximum plastic resistance and on the temperature of coke formation. For rates as low as 1.5" per minute the maximum plastic pressure was lorn as a rule (although for Pocahontas coal it was abnormally high). The temperature of coke formation for the loa heating rates was i n v a r i a b l y low. S i n c e t h k extrerne h e a t i n g rates which these investigators experimented w i t h tended t o give variable r e su 1t s , and since higher r a t e s experimented with in the FIGURE 1. RELATION OF RANKOF COAL Bureau of Mines TO STRENGTH OF COKE laboratory led to difficulty in reprorl ucing plastic pressures, an intermediate rate of 3.5"per minute was adopted for this test. It was planned to run the Davis plastometer a t the same rate in order that the plastic resistance and the nitrogen resistance figures should be comparable. The rate realized is 3.4" to 4 " per minute. The heating rate in the Damm-Agde test is 4.2"per minute which is well within the range of ready reproducibility found by Coffman and Layng.
CHEMISTRY
1271
If coked without stirring, however, this coal is known to produce a fine-grained, firm coke. Herein, then, lies a limitation of the plastometer method for estimating strength of coke a coal will produce. Semi-bituminous coals (and those of low bituminous rank as well, Figure 3) do not have strong fusion tendencies and do not therefore exhibit much plasticity. The temperatures marking the point of initial expansion, and the beginning of the plastic range by both the nitrogen resistance method and the plastometer show regular variation n-ith the blend of coal except that for the plastometer the blends of Davis and Ocean coal are not in the expected order. The discrepancy here, however, is small. Furthermore, since these temperatures do not mark the initial points of exactly the same phenomena, they do not necessarily vary by the same law. The initial expansion temperature marks the point where gas begins to be evolved rapidly and is the temperature of initial actire decomposition. Of the two strongest coking coals, Davis and hlary Lee, t h e l a t t e r starts decomposing a t t h e l o w e r temperature; it is a l s o h i g h l y expanding, whereas the Davis is only EFFECTOF BLENDIKG ON PLASTIC RANGETESTRESULTS m o d e r a t e l y so. AND OK THE PROPERTIES OF THE COKEPRODUCED Since the Dhvsical Table I1 shows the results obtained in blending coking properties Of the FIGURE3. RELATION OF PLASTIC REcoals of high rank with others of medium rank, the Davis cokes f r o m these SISTANCE IS PLASTOMETER TO STRENGTH O F COKE and Mary Lee coals being of high rank (low volatile) and the coals a r e practiOcean and Pratt being of medium rank. The shatter and cally the same, it tumbler indices of the cokes show that consistent improve- cannot be argued that coking power varies directly with tendment is realized by blending the Ocean and Pratt coals with ency to expand. This point will be referred to again later. Davis and Mary Lee coals, respectively, and it is known that SIGNIFICANCE OF INITIAL PLASTIC-RANGE CRITICAL this is true from by-product coke-oven practice. The agglutiTEMPERATURES nating Dower varies In Table I11 temperatures of initial expansion, resistance regularly in both cases with theindices of the to passage of nitrogen, and resistance in the plastometer coke a n d w o u l d developed are listed for the twenty-two coals so far studied. doubtless be of some The initial expansion temperature is the point where deservice in predicting composition gases first begin to be evolved rapidly and may s u i t a b l e blends of also be called the "temperature of initial active decomposicoals of t h i s s o r t . tion." At the temperature where resistance to nitrogen The plastic resistance develops, the charge of coal fuses or a t least flows enough by both the plastome- t o form a more or less fused mass. This fact has been verified ter and the nitrogen by observing a particle of coal under the miscroscope while resistance tests varies it is being heated. The temperature where resistance dewith the quality of the velops in the plastometer marks initial resistance to shearcoke, as one would that is, shear between the vanes of the instrument and the expect for Pratt and walls of the retort. It is therefore the point where the mass Mary Lee coals and becomes sticky. Each initial temperature is averaged for all their blend, but their the coals, and, on an average, coal begins to expand and variation is not con- also t o decompose actively, offer resistance to passage to FIGURE 2. RELATION OF NITROGEN sistent for the Ocean- gases, and become sticky within a temperature range of 11" RESISTANCEIN LAYNG-HATHORNE Davis blends. So far C. (389" to 400"). Further, the maximum variation from OF COKE TESTTO STRENGTH as these tests are con- the averages of these critical temperatures is of the order of cerned, therefore, the agglutinating power test gives the most 25". Since the coals given in Table I11 cover practically reliable indication of comparative coking power, and this con- the entire range of rank of American coals used for making clusion is in accord with trends for the twenty-two coals of the coke, it is evident that coals vary but little in their temperaseries shown in Figures 2 to 4. tures of initial softening. Furthermore, if these critical The reason for the anomalous behavior of the plastometer temperatures are to be of use in distinguishing between with the Davis coal is believed to be that this low-volatile different coals of nearly the same rank, it would appear that coal, when stirred, will hardly fuse together and become the temperatures themselves must be determined with a sticky a t all; there is not sufficient fusible substance present. high degree of accuracy and that the process of determination The residues from the tests indicated imperfect fusion. must be carefully standardized. I
~~
"
I
1
I N D U S T R I A L A N D E N G I N E E R I N G C H E 121 I S T H Y
1272
TABLE 111. RELATION OF TEMPERATURES ~ C ~ A R K I KTHE C BEGISNIYG OF
THE
PLASTIC RANGE FIXED C
ASH IN
COAL 16 9 22 12 15 8 20 6 18 7 3 14 1 5 13 2 17 19 21 4
11 10
BED Alma Pittsburgh Pittsburgh Pittsburgh No. 2 Gas M a r y Lee ( a a s h e d ) Thick Freeport Blenda P r a t t (washed) Mary Lee (unu-aehed) Roda Chilton Pittsburgh Blendb Black Creek Elkhorn P r a t t (unwashed) Sunnyside Green River Davis hlichel Orient
ST.4TE
COrNTY
JfINE
W.Va. Pa. 1%'. Va. Pa. W. Va. Ala. Pa. Pa. Ala. -41a. Va. TV. Va. Pa. Pa. Ala. KY. Ala. Utah KY. Md. British Columbia Ill.
Boone Fayette Marion Fayette Kanawha Jefferson Allegheny Allegheny Jefferson Jefferson Wise Logan Allegheny -4llegheny Walker Letcher Jefferson Carbon Muhlenberg Garrett
Spruce River 4 Edenborn Monongah Allison Point Lick 4 Flat Top Wildwood
.
, ,,
.
,
,
.
Franklin
......
Wylam 8 Flat Top Roda 3 Boone 2 Ocean 2
......
Empire KO. 204 Kylam 8 Columbia Green River Arnold hlichel Orient
(MorsTUREAND
DRY ASHC O ~ L FREE) % % 7.3 7.6 6.1 8.6 2.8 8.7 6.5 5.5 3.2 16.1 2.8 4.3 6.1 7.6 2.7 2.2 9.4 6.3 7.4 7.4 6.3 13.4
Vol. 25, No. 11
58.5 62.9 59.5 62.9 59.4 68.5 60.4 64.3 66.4 66.4 62.2 61.3 62.4 69.6 61.8 61.7 66.3 56.6 56.6 75.2 70.8 59.7
Average, Av. deviation of different coals J l a x . deviation from av.
DAMXAGDE TEST 1x1-
INITIaL RESISTANCE LayngPlasEXPANHathorne tometer SION test te(it T I ~ L
c.
c.
383 394 387 :374 388 384 381 399 404 382 388 385 395 407 388 415 $07 ,390
-
389
.25. .
401 407 406 405
-
394 11 21
"C 396 393 389 39 1 406 :383 393 407 405 393 408 395 387 395 408 420 398c
...
411 426c
. . 400
...
26
20 per cent Davis and 80 per cent Warden coal. b 40 per cent Davis and 60 per cent Warden coal. c These coals developed no resistance in t h e plastometer.
a
As to the relative merits of the three test methods for showing the beginning of the plastic range, it is somewhat difficult to decide on the basis of results obtained so far. The Damm-Agde test gives an indication of the initial contraction temperature (from 40" to 160" C. below the fusion temperature) which the other two tests do not give. It is believed that this indication is worth while because the weakly coking coals 10, 19, and 21 begin t o contract at low temperatures as compared a-ith those of stronger coking properties. The interval between initial contraction and initial expansion (the latter is not greatly different from that for other coals) is large, being over 100". If this behavior is borne out by tests of other coals, it must mean that a long contraction interval connotes poor coking power. The Damm-Agde test, therefore, gives more information as to i n i t i a1 plastic-range phenomena than the other two. Between the initial expansion, initial n i t r o g e n resistance, and i n i t i a l plastic resistance temperatures as measured b y t h e i r respective tests, t h e r e s e e m s little to c h o o s e ; alt h o u g h these temperatures do not mark exactly t h e same changes taking place in the mass as previously s t a t e d , i t so FIGURE 4 . RELATION OFAGGLUTINATh a p p e n s t h a t the ING POWER TO STRENGTH OF COKE changes take place at very nearly one and the same temperature for a given coal, and one indication can have no greater value than the others for indicating carbonizing properties.
CORRELATION OF PLASTIC PROPERTIES OF COALWITH QUALITYOF COKEPRODUCED
THE
In order to make the results comparable, the same rate of heating was maintained in the plastic range tests as that prevailing in the 800" to 900" C. carbonization tests of the
>urvey. The average of the 1.5-inch (3.81-cm.) h a t t e r and the 1-inch (2.54-cm.) tumbler indices was chosen as a practical measure of quality of coke, measurements being made in accordance with the standardized methods of the American Society for Testing Materials. As an absolute meawre of coke quality, these indices mobablv fall short _of &at cou"ld herdesired, and t h e r e f o r e exact correlation wit11 9 p l a s t i c properties for 5 90 this reabon alone could ; not be expected. However, such coke tests do 5 furnibh a good measure of the handling properj ties of a coke, and this mas one of the main objectives of the engineers who designed and s t a n d a r d i z e d t 11 e FIGURE5 . RELATIONBETMEEN tPStS PLASTIC RANGEA S D STRENGTH O F The relatioll of rank C O K E , L 4 Y N G - H A T H O R \ E TEST of the coal to the quality of coke for the twenty-two coals is shown in Figure 1, rank being based on content of total carbon, and quality of coke on shatter and tumbler indices. It is probable that the correlation is as good as could be expected, considering that the methods of measuring both properties in question are admittedly approximate. Grade of the coal apparently has an effect, for coal 17 is of exactly the same rank as coal 18 but it contains about three times as much mineral matter and is therefore of much lower grade. Furthermore, coal 17 is out of line with the average in the figures which follow. Figures 2 to 4 show the extent of correlation obtained for the twenty-tFo coals studied between quality of coke and resistance to nitrogen, resistance to shear, and agglutinating power, respectively. These properties are roughly proportional to the quality of the coke, which has been shown to be roughly proportional to the rank of the coal. It seems probable that, if due consideration were given to the grade of the coal (as well as rank) and that if greater refinement were resorted to in the plastic measurements themselves, closer correlation could be lm
i 7 0
J M
zd
November, 1933
IN D U S TR IAL A N D EN GI N E ER IN G CH EM I STR Y
realized. Realizing the empirical nature of the tests, further refinement should probably first consist in making a larger number of repeat tests and using the average. Mott and Wheeler (4) claim that there is an important relation between expansion properties of a coal and the strength of coke which it will produce, when expansion is determined by the Sheffield laboratory test. They conclude, in particular, that a coal must expand at least 25 per cent in order to produce a good coke. I n Table IV the expansion of the coals of the group considered in this p a p e r is given, expansion being determ i n e d b y t h e B u r e a u of Mines method which is similar to, but not e x a c t l y the same as that used a t Sheffield. The strongest coking coals of the series fill the Mott and mheeler requirernent of 25 per cent expansion. On the other h a n d , the coals expanding FIGURE6. R E L A T I O BXE TWEEK PLASTIC RAKGEA N D most are not those that proSTRENGTHOF COKE, P L ~ s - duce the s t r o n g e s t cokes. TOMETER hfott and Wheeler's discussion leads one to believe this is true, although they state that it is not invariably so. The Sheffield test differs from that used by the Bureau of Mines in that in the latter case free expansion is measured and in the former the charge is under a slight load. This difference would probably cause some difference in the results. STRENGTH OF COKEAND LENGTH OF PLASTIC RAKGE I n Figures 5 and 6 the length of the plastic range for the Layng-Hathorne test and the plastometer, respectively, is plotted against the strength of the coke, strength being measured by the average of the 1.5-inch shatter and 1-inch tumbler indices of cokes made a t 800" C. There is some relationship, but it is admittedly rough. Perhaps the best interpretation is that both high-rank, strongly coking coals and low-rank, weakly coking coals have short plastic ranges and that the ranges of coals lying in between tend to increase with coking power. The Layng-Hathorne ranges for the highest rank coals, 4 and 11, are believed to be misleading. Because of the known lack of aftershrinkage in these coals, the plug of coke in the reaction tube remains impervious to gas long after it has actually set. These coals do not contain sufficient volatile matter to become fluid in the plastometer; apparently such volatile matter as they contain possesses very strong coke-cementing power, for they do produce strong cokes. Furthermore, they have high agglutinating powers a t moderate dilution with inert; but the strength of the test buttons falls off rapidly with increasing dilution. Low-rank coals 10, 19, and 21 have low plasticity (none a t all in the plastometer); apparently there is just enough fusion to plug the reaction tube in the nitrogen resistance test over a short range of temperature. I n the test retort a t 500' C. they did not produce a coherent coke a t all. Coals 5, 6, 8, 9, and 12 have long plastic ranges by both methods and they produce moderately strong cokes. It can be argued that these coals have sufficient aftershrinkage properties, since they are regularly coked in ovens without pushing troubles. Coals 2, 3, 13-16 are similar as regards rank, strength of coke, and petrography; they would be expected to have plastic ranges of about the same length, and they do by the plastometer test. By the nitrogen resistance test the points are scattered over a wider range,
1273
For this reason and because of bhe interference of nonshrinkage in the Layng-Hathorne test, the plastometer is believed to give the better measure of the length of plastic range. TABLEIV. SWELIJNG TESDEKCIES OF COALS
COlL B E D
MINE
AV. SH.ATTERSWELLhIOISTURE- AND AND ING ASH-FREEC.ARBOB TUMBLER TENDFixed Total INDICES EBCY
% COALS SWELLING
Mary Lee" Pittsburgh Pittsburgh Pittsburgh Alma Pratt" Roda Pittsburgh Blendb Mary LeeC Thick Freeport PrattC
Flat Top Edenborn Allison Monongah Spruce River 4 C0.ALS S W E L L I N G Wylam 8 Roda 3 Ocean 2
......
Flat Top Wildnood M'ylam 8
loo
zeo 68.5 62.9 62.9 59.5 58.5
TO
%
%
%
82.8
260e 200e 150C 127 110
PER CENT
87.1 85.5 85.1 84.6 84.5
68.0 73.0 61.9 60.9
50 T O I00 P E R C E N T
66.4 62.2 62.4 69.6 66.4 60.4 66.3
86.8 86.3 85.4 86:2 84.0 86.3
66.7 65.0 56.7 79.4 69.9 64.3 43.1
80C
70 70 60e 60e
60
60
C0.4LS S W E L L I N G 50 P E R C E N T A N D LESS
Davis Arnold 75.2 87.9 82.5 5Oe Blendd ..... 64.3 77.8 506 Michel &fiche1 70.8 87:4 78.7 3.5e ~. Elkhorn No. 204 61.7 84.6 62.8 20 Chilton Boone 2 61.3 84.8 65.5 10 Black Creek Empire 61.8 84.0 61.4 10 Sunnyside Columbia 56.6 81.5 29.0 0 Green River Green River 56.6 80.3 46.0 10 a Washed coal. b Blend of 60 per cent Davis with 40 per cent Pittsburgh coal. c Unwashed coal. d Blend of 20 per cent Davis with 80 per cent Pittsburgh coal. e Coals having a combined shatter and tumbler index greater t h a n 65.5 per cent
COMPARISON OF KITROGEN RESISTANCE WITH RESISTAXCE IN THE PLASTOVETER DEVELOPED It would seem that the more sticky (highly viscous) the fused mass of a coking coal becomes just before it sets into coke, the stronger the resulting coke; but this is not necessarily so, for high viscosity a t this point might result in retention of large bubbles of gases, rendering the coke highly porous and weak. Figures 2 and 3 do show for this series of coals that the strength of coke formed is roughly proportional to the maximum viscosity of the mass whether maximum viscosity is measured by the nitrogen resistance method or by the plastometer. It is of interest to see how the results by the two methods measurement compare among themselves. Table V gives the results arranged in the order of decreasing viscosity as measUredbY the nitrogen FIGURE7. RELATIONOF APPARENT resistance method. SPECIFIC GRAIITYOF COKETO RANK The resulting order OF COAL by the plastometer is not in exact agreement with that of the nitrogen resistance method. The coals furthest out of line are 4, 3, 15, and 22. Coal 4 produces the strongest coke of the series, and the plastometer indication is too low as compared with that for the coals immediately following. On the other hand, the coke is very little better than that for coal 8 and the nitrogen resistance figure may therefore be taken as too high comparatively. This is a coal having little aftershrinkage as shown by retort tests, and this property tends to give high maximum resistance in the nitrogen resistance test. Coals 2 and 3 are similar and should not give very different maximum viscosity as the plastometer shows. This statement applies also to coals 15 and 16. Coals 1, 9, 12, and 22 are of nearly the same rank and are from the same bed. Their maximum viscosity is more nearly the same by the plastometer than by the nitrogen resistance method, and they
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INDUSTRIAL AND ENGINEERING CHEMISTRY
1274
Vol. 25, No. 11
would not be expected to differ greatly in this respect. It is believed that the plastometer is the best of the two tests for measurement of maximum viscosity, mainly because it is independent of the variations introduced by lack of aftershrinkage.
strong indication that both are of real significance relative to coking power. 2. For coals of intermediate rank the length of the plastic range as measured by the nitrogen resistance test agrees fairly well with that measured by the plastometer; for coals of highest coking rank and for those of low rank there is lack RELATION OF POROSITY AND APPARENT SPECIFICGRAVITY of agreement. The tendency of these coals to slow afterOF COKETO RANKOF COAL contraction, rendering the mass impervious to gas after the coke has set, causes the setting temperature to b e uncertain Shattei and tumbler indices of cokes have been used as a in the nitrogen resistance method. Coals giving the strongest measure of their quality, and it has been shown that the cokes and those giving the weakest have short plastic ranges; quality so measured bears a rough relationship to the rank for intermediate coals, the strength of the coke tends to of the coal used and to its plastic properties. Porosity vary directly with the length of the plastic range. and apparent specific gravity have also been suggested to 3. The results of the Damm-Agde test do not show direct indicate quality of coke; that is, the higher the apparent proportionality between percentage expansion and strength specific a r a v i t v of coke. However, coals expanding less than 25 per cent and the lloTVer do not produce good cokes, and this agrees with work of other s p a c e , t h e investigators cited. better the coke is 4. The temperature range covered by initial plastic-range ‘Onsidered. It is phenomena-development of resistance to passage of gas known that these and to shear, expansion, and evolution of gas-is narrow. properties can be On an average these phenomena are covered by 11’ a t varied by approximately 400’ C. FIGURE8. RELATIONBETWEEN CELL changing the con5 . Critical initial temperatures may be measured easily SPACE O F COKE A N D RANKOF COAL ditions under within 1’ or 2’ C.; the end temperature of the plastic range which a given coal is measured most accurately by the plastometer. is carbonized (for example, by varying the density of the charge), but little is known as to their variation with rank LITERATURE CITED of coal used when the carbonizing conditions are kept constant. The carbonizing conditions for the coals considered (1) Coffman, A., and Layng, T., IND.ENQ.CHEM.,20, 165-70 (1928). in this paper were kept constant. Figures 7 and 8 give the (2) Fieldner, A. C., Davis, J. D., and Reynolds, D. A., Ibid., 22, 1113-23 (1930). variation of specific gravity and porosity with rank of coal. (3) Fieldner, A. C., Davis, J. D., Thiessen, R., Kester, E. B., and These figures show that coals of low coking rank have low Selvig, W. .1., Bur. Mines, Bull. 244 (1931). apparent specific gravities and high porosities, or high per- (4) hlott, R . A . , and Wheeler, R. V., “Coke for Blast Furnaces,” Colliery Guardian Co., Ltd., London, 1930. centages of cell space, but for coals of medium and high coking rank the variation with rank is small. R E C E I V E D June 21, 1933. Presented before t h e Division of Gas and Fuel Chemistry a t t h e 85th Meeting of t h e American Chemical Society, Washing-
TABLE V. RELATION OF PLASTIC PRESSURE RESULTS, NITROGEN ton, D . C . , March 26 t o 31, 1933. Published b y permission of t h e Director RESISTAXCE, AND PLASTOMETER TESTS of t h e Bureau of Mines, T h e Carnegie Institute of Technology, a n d t h e Mining Advisory Board. (Not subject t o copyright.) Bernard Juettner and AV. AV. SHAT-
SHATTER
TER
MAX. AND MAX. PLAS- TuxN TOMETER BLER
COAL ANCB Mm. H z 0 Kg.-cm.
0
4 774 29.7 520 55.9 8 414 40.9 6 55.0 11 400 19.2 3 380 49.5 7 371 25.3 5 307 12 37.2 280 40.0 1 263 15 260 7.0 2 255 24.2 Unwashed coal, high i n
MAX.
AND
ANCE
DICES
D. A. Wallace were research fellows, Bureau of Mines and Carnegie Instit u t e of Technology, Pittsburgh, Pa.
MAX. PLAS- TuxN TOMETER BLER RESIST- IN-
R-w--
% 82.5 82.8 79.4 78.7 65.0 69.9 77.8 73.0 56.7 6218 ash.
Mm. Hz0 9 18 17a 14 22 20 16 13 21 19 10
250 233 218 188 180 178 177 172 55 53 26
Kg.-cm.
29.1 20.4 21.4 15.2 39.6 28.2 5.9 13.1 0.0 0.0 0.0
% 68.0 66.7 43.1 65.5 61.9 64.3 60.9 61.4 46.0 29.0 48.5
CONCLUSIONS 1. Resistance to passage of nitrogen in the Layng-Hathorne method, stickiness in the plastometer, and agglutinating power of the coals are roughly proportional to the shatter and tumbler indices of the cokes. The agglutinating power furnishes the best measure of this property. It seems probable that the other two tests can be made to correlate better by using the average of a larger number of repeat tests. It is shown that there is approximate agreement of plastic pressure measured by the plastometer with that measured by the nitrogen resistance method; that is, both measurements vary roughly with the coking power as measured by the shatter and tumbler tests and in the same way. The fact that there is even approximate agreement in the measurements of this property by two different methods is
Correction In my article entitled “Anode Process for Rubber Articles and Coatings” [IND.ENQ.CHEM.,25, 609-13 (1933)l the first paragraph in the second column on page 610 should read: “The deposition factor of latex mixes increases rapidly with concentration. For example, 35 per cent mixes of normal pH and conductivity may have deposition factors of 1.2 to 1.5 grams of dry deposit per ampere minute, but, when the concentration is increased to 55 per cent, the deposition factor is often two to four times as great. When it is considered that even 1.5 grams per ampere minute is over 2400 grams per faraday, the deposition rate of even the dilute mixes is remarkable. For example, the above figure is about seventy-three times the theoretical cathodic deposition rate of zinc. Taking the specific gravity of zinc as 7 and that of the rubber compound as 1, the rate of building up the thickness of deposits is 73 X 7 or 511 times as fast with the rubber as with zinc. Since, however, the voltage used to deposit the rubber is usually about five to ten times that used for metal plating, the thickness of rubber obtained per kilowatt hour from a mix having a deposition factor of 1.5 grams per ampere minute is only 50 to 100 times greater than that obtained in plating zinc.” In the first sentence in the second paragraph in the second column on page 610, “or dialysis” should be deleted. C.L. BEAL
