Development of Dakota Lignite IX. Effect of Inorganic Materials on Low-Temperature Carbonization of Lignite A. W. KOTHAND IRVINLAVINE,University of North Dakota, Grand Forks, N. Dak.
I
NORGAIIL'IC salts have been f o u n d to influence the nature of the carbonization p r o c e s s for both coking and n o n c o k i n g coals. With coking coals the structure of the coke as well as its r e a c t i v i t y may be altered by the addition of c e r t a i n inorganic materials (2, 3, 11). T h e e f f e c t of inorganic salts on the nature of the carbonization process with lignite is being studied in this laboratory (7, 9). The present paper reports the results of one phase of this study with freshly mined lignite and with lignite that was dehydrated previously by steam (4, 8, 10).
Certain inorganic compounds present in the inherent ash of lignite p l a y an important role in determining the nature of the low-temperature carbonization process. This becomes evident from a study of the inJluence of certain inorganic reagents on the carbonization process. The salts A lz (SO,)3. 18H20 and A 1Ck6H20 cause cementation to a degree suficient to yield a coherent pseudocoke. T h e removal of the greater portion of the inherent ash f r o m the lignite increases the effectiveness of the A12(S04)3.18Hz0 in this respect but does not influence the yield of char, tar, and gas. O n the other hand, the removal of the sodium hydroxide-soluble humates f r o m the lignite changes entirely the nafure of the carbonization process in the presence of AlzEXPERIMEKTAL PROCEDURE (SO,)3.18HzO . The influence of inorganic salts is quite S O U R C E OS F M A T E R I A L S . different with steam-dried lignite. This is due The lignite used in this investiprobably to a reduction in content and a change g a t i o n was obtained from the T r u a x - T r a e r mines at. Velva in the quality of the inherent ash in the lignite.
and Wilton, N. Dak. The coal was shipped d i r e c t l y to t h i s laboratory in sealed containers and arrived with a minimum loss of moisture. A portion of the lignite was air-dried and used directly for the work of this investigation. Separate portions were extracted with hydrogen chloride and with sodium hydroxide solutions for study. Samples of the steam-dried lignite were taken immediately after being processed by a method described in an earlier paper (IO). ANALYSES OF LIGNITES. The proximate analyses of the lignites as used in this investigation are given in Table 11. INORGANIC SALTS. The inorganic salts used are as follows. Na2C03, CaC03, FeC&6H20, MgC12.6H20, MC13 6Hz0, and Alz(SO4)3.18H20. The c. P. grade was used in each case. I n one series of experiments the effect of humic acid was studied. This acid was obtained by the extraction of Velva lignite with a 10 per cent sodium hydroxide solution and subsequent precipitation with hydrogen chloride solution. The humic acid was washed and dried a t 105" C. Analyses of the material gave the following results: T" Moisture Volatile matter Fixed carbon Ash Sulfur
2:3 41.5
53.9 2.3
0.5
% Carbon 64.0 4.1 Hydrogen Oxygen (by difference) 31.9 9942 B. t. u. per lb.
APPARATUS.The carbonizing apparatus used in this investigation is illustrated in Figure 1. More complete details as to this set-up can be obtained from previous publications (6, 7 ) . PROCEDURE. The lump coal was first air-dried and then ground and sized. In the earlier investigation the coal was ground to pass through a 20-mesh screen and used as such. It has since been found that the particle size does influence the
structure of the resulting coke, and therefore a mixture of predetermined sizes which gave the best results was used throughout this work. After the proper mixture had been p r e p a r e d by c a r e f u l l y weighing predetermined quantities of each size, a quantity of the m i x t u r e weighing 142.5 grams wasplaced in a mortar and the predetermined quantity of i n o r g a n i c salt and water was added. T h e FeCL.6H20 and MgC12.6Hz0, because of t h e i r high solubility, were added by dissolving the given w e i g h t of salt in the predetermined quantity of water and then mixing the solution with the coal. However, with the other salts used, it was found preferable to add them in the dry state by mixing the pulverized salt (- 150 mesh) intimately with the coal and t h e n a d d i n g t h e g i v e n a u a n t i t v of water. Briauets [1"/1&inches (4.29 cm.) in diameter a n i ll/ainches (3.18cm.) in height] of the mixture were formed at a pressure of 1800 pounds per square inch (126.5 kg. per sq. cm.) in a mold placed in a Riehle compression machine. The use of this machine permitted easy duplication of the briquetting pressure. The briquets were placed in a small aluminum basket which was then weighed and placed in the retort proper. The use of the basket facilitated the removal of the coke residue. The weights of the flask and filter having been obtained previously, the rest of the train was connected and the retort heated to 500' C. in 15 minutes a t as uniform a rate as possible. The temperature was held a t 500' to 510" C. for 1.5 hours. Upon completion of the heating, the final volume of the gas waS recorded together with its temperature. The barometric pressure was read a t the same time. The U-tube was removed from the train and dried in a constant-temperature oven for one hour a t 105" C. with a small steady current of air flowing through the tube. The weight of tar was then calculated. The separation of the tar from the distillate was rather difficult because of the low tar yields. The xylene distillation method employed by Gauger and Salley (7) proved unsatisfactory because coal dust was always carried over with the gas stream and in some cases it was found that considerable inorganic material distilled with the tar and water. The following method was finally adopted although it still retains certain inherent difficulties: The contents of the flask was poured into a 400-cc. beaker, after which the flask was rinsed with xylene. The solution was evaporated to dryness and the residue was extracted several times with xylene to dissolve the tar. The solution was then filtered into a weighed
328
I S D U S T R I h L A N D E N G I N E E R I N G C H E hl I S T R Y
LIarch, 1933
329
beaker and was evaporated to dryness on a steam bath. experiment 9 (Table 111) which contained 40 per cent of the 40 mesh, and 23 per cent of -200 mesh, together The beaker was reweighed and the weight of tar calculated. size -20 The weight of tar obtained in this separation was added to the with smaller quantities of intervening sizes. Having ascertained that such a mixture gave the best result, it was tar obtained from the U-tube for the weight of total tar. A representative sample of the gas was obtained from the decided t o utilize identical mixtures in all of the carbonizagas holder after 5 liters of gas had been expelled through the tion work of this investigation. The authors realize that, sampling device The sample was then analyzed in a United although this mixture gave the best results with the d l C 1 ~ States Steel Corporation modified Orsat apparatus by the 6H20,a mixture of other size particles might be better suited for the other salts used in this work. Further work along usual method. Bfter the retort had cooled sufficiently, the (char was re- this line is to be carried on in this laboratory. moved, weighed, and bottled. In the case of the noncoherent residues a sizing test of a representative portion of the char was made to determine if any change had occurred. The coherent residues were pulverized by hand for use in other F experiments and bottled. Proximate analyses were made with all chars. COMPOSITION OF MIXTURES. The composition of the various mixtures used are listed in Table I. These represent an amount of reagent equivalent to 5 per cent of the compound formed, with exception of the A12(S04)3.18H20,in which case 5.5 per cent mas used since this amount gave better results. The FeCl3.6H20 .a-as taken to change to Fe203. The MgC126H20 mas assumed to remain as the anhydrous FIGURE 1. ASSEMBLYO F APPARATUSFOR CARUONIZ.4TION salt. The CaC03 and Na2C03 were assumed to remain STUDIES unchanged, and the hydrated chloride and sulfate of alumi9. Thermocouple G . Gas holder num were assumed to change to the oxide. Gauger and B. Gas furnace €2 Potentiometer C . Water condenser, J. Aluminum retort Salley (7) assumed that all of these compounds, with the D. Condensing receiver K . Cold junotion E. Tar filter L. Gas sample receiver exception of the n'azC03,changed to the higher oxide. DurF. Gas eampling tube ing the latter part of the present investigation certain evidence was obtained which indicated that the hydrated alumiRAWVELVALIONITE num sulfate remained as the anhydrous salt. CARBONZATION PRODUCTS. A consideration of the data Experimental results are summarized in Table 11. for the air-dried raw Velva lignite shows the inorganic salts t o influence the yields of products as follows: EFFECTOF PARTICLE SIZE All of the reagents caused an increase in the char yield; the The catalytic coking of lignite consists largely in a reacincreases were obtained with the humic acid and A12tion that causes a cementation of the carbonized particles. largest (S04)3.18HzO. Surface and, therefore, particle size play an important role. Humic acid and 9azC03 caused a small increase in tar yield; To determine the effect of particle size, a series of runs was the other reagents caused a definite decrease. The decrease in made with lignite mixtures composed of predetermined pro- tar yield Kith the FeCI3.6HzOamounted to 38.5 per cent in comportions of particle sizes. In each case the lignite was mixed parison t o the blank run. This decrease is far greater than that obtained with any of the other reagents. with A1C13.6H20and mater in the proportions given by the All of the reagents, with the exception of the humic acid, data for experiment 6 in Table I. caused an increase in gas yield. The largest increase (22.7 per cent) was obtained with the Na2CO3. TABLEI. COMPOSITION OF MIXTURES USEDIN CARCHARS. The chars obtained with addition of Xa2CO3, BONIZATIOS WORK CaC03, MgC12.6H20, and FeC18.6HzO showed no evidence LIQSITE~ 4TER EXPT. Source Condition RE.4GENT .kDDED ADDED of cementation or coking. Although the briquets retained Grams Grams their shape during carbonization, they crumbled into a mass of .iir-dried 30 1 Velva ... fine particles upon being removed from the aluminum basket. Air-dried 7.50 28 2 Velva Air-dried 54.30 28 3 Velva Gauger and Salley (7) found that the addition of MgC12.6H20 28 Air-dried 15.97 4 Velva .kir-dried 7.50 33 5 Velva did alter the structure of the residue, but it should be rememAir-dried 35.52 25 6 Velva bered that they added the salt on the oxide basis and, there.4ir-dried 25.28 28 7 Velva HC1 washed, 30 Velva 8 fore, added a larger weight proportion. A very hard residue 54:30 20 Velva 9 then air-dried Velva 10 NaOH extracted, 30 was produced by AlCla.6Hz0 and 8ly(8O4)3.18Hz0 which has 54: i o 20 11 Velva then air-dried been named pseudocoke (7). The core of these cokes was Air-dried 14.25 12 Velva 30 13 Wilton somewhat softer than the outside and did not possess the 54: 30 14 Wilton gray metallic luster exhibited by the outer surface. HowWilton 7.50 15 Wilton 25.28 16 ever, under the microscope the coked lignite particles apSteam-dried 7.50 Wilton 17 U'ilton Steam-dried 15.97 18 peared well cemented throughout the entire briquet. Wilton Steam-dried 35.52 19 The addition of humic acid (10 per cent based on weight of 30 20 Velva Steam-dried ... 7.50 33 21 Velva Steam-dried coal used) to the air-dried Velva lignite did not produce a 22 Velva Steam-dried 25.28 2 8 change in the character of the char residue. The briquet 15.97 28 23 Velva Steam-dried 24 Velva Steam-dried 7.50 2s retained its shape but crumbled upon being removed from 25 Velva Steam-dried 35.52 20 54 30 26 Velva Steam-dried 20 the basket. 142.5 grams used in all experiments. The analyses of the chars in this series show that the ash contents have been increased in every case except the humic Table 111 gives data as t o the particle-size mixtures em- acid experiment. However, a simple calculation shows that ployed and also a brief description of the resulting residues. the reduction of ash in the latter case is due to a dilution The best residue was obtained with the mixture used in because of the low ash content of the original humic acid.
+
I
I
~~
0
INDU STR IA L A N D EN GI X EER IN G C H E M ISTR Y
330
The ash contents of the chars vary from approximately 15 per cent in the blank char to over 23 per cent in the Alz(S04)3.18H20char. If the chars are listed in their order of increasing ash contents, they fall also in the order of increasing molecular weights of the inorganic salts as follows: blank, MgClz, CaC03, Na&03, A1C13, Fez03,and A12(S04)a. The volatile matter contents of the chars are worthy of note. Table I1 shows that the Alz(S04)3.18Hz0char possessed the highest content of volatile matter. This might indicate that carbonization was not as thorough in this instance as in the other experiments. However, it will be shown later in this paper that this is not the case. Rather, this high volatile content with Alz(S04)3.18Hz0chars is due, probably, to the decomposition of aluminum sulfate. SCREENANALYSES OF CHARS. The screen analyses of the chars as given in Table I1 show that the addition of Na2C03, FeC13.6Hz0,and humic acid increased the percentage of the larger-sized particles when a comparison is made with the screen analysis of the blank char. This is indicative of some cementation. The addition of MgCl2.6H20 and CaC03 caused little change in this respect. The aluminum salts, of course, yielded coherent residues. GASANALYSES.The data in Table I1 show further that, with exception of the aluminum salts, the inorganic salts introduced little change in the character of the gas. A noticeable increase in carbon dioxide was obtained with the Alz(SOa)3.18H~0,whereas addition of AlC13.6H20 caused a decrease in carbon dioxide. EXTRACTED VEI.PA LIGKITE I n any study dealing with the effect of inorganic salts on the carbonization of coal, it is important to realize that the inherent ash of the coal might play an important role. For theoretical studies it is advantageous to work either with a fuel of low ash content or to remove the inherent ash by treatment with acid. Although the present investigation was concerned primarily with the determination of the effect of the inorganic salts in the presence of the inherent ash in the coal, two series of experiments were made with acid-extracted and with alkali-extracted lignite. Data for this work are given in Table 11.
v01. 23. No. 3
PREPARATION OF EXTRACTED COAL. The acid-extracted Velva lignite was prepared by washing the coal (without heating) with 1:1 hydrogen chloride solution until no further reduction in ash was obtained. The coal residue was then washed thoroughly with distilled water until free from acid. The alkali-extracted lignite was prepared by washing a quantity of Velva lignite for 5 days on a steam bath with a 10 per cent solution of sodium hydroxide. The solution was decanted and the residue mashed with a fresh portion of the alkali. The solution was decanted again and the coal residue washed thoroughly with distilled water until free from alkali. The humic acids were precipitated from the mother liquor and washings by the method described earlier in this paper. EFFECTOB REMOVAL OF INHEREST .ISH The influence of the inherent ash in Velva B L A ~CHAR. ~K lignite on the nature of the carbonization process can be best determined by comparing the results of experiments 1 and 8: The character of the char residue is not altered. In either case the residue is noncoherent and exhibits no apparent coking of the particles. The char and tar yields are approximately the same. The gas yield in the case of the acid-washed blank is somewhat smaller than in the case of the raw blank. The ash content of the acid-washed blank char is less than the ash content of the raw blank char. The volatile matter contents of the two chars are approximately the same. The removal of the larger portion of the inherent ash causes an increase in the carbon monoxide and ethane contents of the gas and a decrease in the percentages of carbon dioxide and hydrogen.
EFFECTOF Alz(S04)3~18Hz0.The removal of the greater portion of the inherent ash in lignite increases the effectiveness of the &(so4)3. BHzO in producing a hard, coherent residue. The pseudocoke in this case was the best residue obtained during the course of the investigation. It was coherent, hard, and free from cracks, and exhibited a marked gray metallic luster. A comparison of the data for experiments 9 and 3 shows that the yields of gas, tar, and char in these two instances do not differ materially. Evidently, then, the influence of the Al2(SO4)3~18HZO on the yields of the carbonization products TABLE11. LOW-TEMPERA-
TYPEOF LIGNITEA N D PROXIMATE ANALY~IS
EXPT. 1 2 3 4 5 6 7 12
Velva, air-dried Hz0 12.7% V. m. 3 8 . 6 % F. C. 3 9 . 5 % Ash 9.2%
Velva extd. with HC1 H 2 0 7.9%' F. c . 45.7%; 1'. m. 44.7'%; ash 1.7%
8
Velva extd. with NaOH H,0 11 2 % . F. c. 40.7% V. m. 3S,6%: ash 9.5% Wilton, steam-dried Hz0 10.5% V. m. 4 4 . 5 % F. C. 41.5% Ash 3.5%
Velva, steam-dried Ha0 1 3 . 3 7 ~ V. m. 39.6% F. c . 3 9 . 8 % Ash 7.3% 0
Volatile matter,
REAGENT
Blank
NazCOa
Ah(SO4)a*18HzO MgCIz.6HzO
CaCOa
AIC13.6HzO FeCIa*6HzO Humic acid
YIELDP E R 100 G. DRYASH-FREECOAL Drv ch&, DEVIATIOS F R O M BLANK ashGas, Tar Gas free Tar S. T. P. Char % % Grams Grams Liters % 0.0 0.0 0.0 3.48 12.3 64.6 0.3 +27.7 0.8 3.49 15.1 65.1 - 2.0 +17.9 +12.1 3.41 14.5 72.4 - 6.9 +13.8 4.5 3.24 14.0 67.5 - 2.6 +17.9 5.0 14.5 6 7 . 8 3.39 -10.3 +1S.7 7.3 3.12 14.6 69.3 -38.5 +14.6 8.4 2.14 14.1 70.0 2 . 6 1.6 +13.1 3.57 12.1 73.1
I
Illumi-
GAS
Ash
%
F. c . b %
%
%
-
17.8 18.5 22.9 13.7 20.9 13.8 13.7 18.6
67.5 62.3 53.i 69.7 60.7 65.8 66.2 68.3
14.7 19.2 23.4 16.6 18.4 20.4 20.1 13.1
54.2 51.8 63.0 52.6 51.4 46.5 52.3 45.7
3.4 2.9 2.6 3.1 3.5 4.0 2.9 3.1
1.2 1.7 2.2 1.3 1.9 4.1 1.7 1.3
0.0 5.5
+ 08 .. 07
17.4 22.4
79.4 64.2
3.2 13.4
46.8 59.1
3.5 3.0
1.8 1.4
0.0 9.1
0.0 -33.6
0.0 -10.9
17.2 20.1
67.8 54.9
15.0 25.0
51.6 68.8
2 7 3 8
1.9 0.6
0.0
0.0 +-13.4 4.0 ++
0.0 2.6 9.3 - 2.5 - 4.3 - 4.3 6.8
16.6 21.8 17.7 13.2 20.2 14.2 13.8
77.9 63.2 69.7 74.1 70.1 76.8 73.4
5.5 15.0 12.6 12.7 9.7 9.0 12.8
33.7 51.8 46.6 32.0 38.9 34.8 22.0
3.0 1.9 2.0 3.1 2.4 3.8 3 9
1.6 1.7 0.9 1.5 0.9 1.4 3.0
0.0
18.2 20.1 13.6 13.5 18.6 14.1 21.8
69.8 64.9 68.4 71.7 64.3 67.7 54.8
12.0 15.0 18.0 14.8 17.1 18.2 23.4
48.8 52.9 51.2
3.2 2.3 1.8 3.5 3.9 3.3 2.5
1.0 0.9 1.1 1.0 0.7 1.2 0.9
+
+
+ + ++
+
Blank Alz(SOd8*18H~O
62.5 74.6
3.65 3.45
11.6 12.7
0.0 +19.4
10 11
Blank Alz(SOd3.18HzO
62.7 6S.4
3.24 2.15
13.8 12.3
+
13 14 15 16 17 18 19
Blank A1z(S04)3~18HzO NazC03 FeCh.6HzO CaCO3 M Clz.6HzO A1&13.6HzO
63.7 74.4 64.7 69.1 67.1 66.2 66.6
1.49 1.55 1.29 0.79 2.67 2.25 1.37
11.8 12.1 12.9 11.5 11.3 11.3 12.6
20 Blank CaC03 21 22 FeCh.6HzO MgClz.6HzO 23 24 NazCOs 25 AlCh.6Hg0 26 A1z(SOila~18HzO b Fixed carbon.
65.5 67.2 68.9 70.9 65.0 68.5 69.8
1.84 1.89 1.25 1.52 1.23 1.68 1.19
12.6 11.8 12.7 12.4 13.6 10.5 10.2
9
P H O X I M l T E ANALYSIS OF DRYCHAR
+16.8
+ + + + +
1.6 s.5 5.3 3.9 4.6
++ ++ +
0.0 2.6 5.2 8.2 0.8 4.6 6.6
-
-47.0 +79.2 +51.0 - 8.1
0.0 2.7 -32.1 -17.5 -33.2 - 8.7 -35.5
+
+
+-- 601... 386
+-16.7 7.9 -19.1
V. m.a
%
COz
53.0
56.0 42.3 65.1
natinp
Oz
%
INDUSTRIAL AND ENGINEERING CHEMISTRY
March, 1933
is not altered greatly by the removal of the greater portion of the inherent ash of the lignite. EFFECTOF REMOVAL O F HUMICACID BLANKCHAR. The influence of the sodium hydroxidesoluble humic acids in Velva lignite on the products of carbonization can be determined by a comparison of the results of experiments 1 and 10. This shows that the removal of these acids causes but little change in the character of the char residue and also in the yields of char, tar, and gas. Furthermore, the analyses of the char and gas in these two cases are approximately the same. EFFECTOF A12(S04)318Hz0. The removal of the sodium hydroxide-soluble humic acids from the lignite alters considerably the influence of the aluminum sulfate hydrate in the carbonization process. The addition of this salt to the alkali-extracted coal produced a char that was noncoherent, crumbled upon being removed from the retort, and exhibited but slight evidence of coking. Furthermore, a comparison of the results for the &(SO4)3.18H20 chars with raw and alkali-extracted lignite (experiments 3 and 11) shows that the removal of the humic acids reduces to a marked extent the char, tar, and gas yields. Also, the carbon dioxide content of the gas is increased, and the other constituents are decreased. Evidently the greater part of the organic materials (presumably humus in character) upon which the Alz(S04)s 18Hz0 acts during the carbonization has been removed or hydrolyzed by the action of the alkali. This removal introduces a marked change in the action of Alz(S04)318H20on the nature of the carbonization process.
331
fuel had the same or less percentage of ash than the original fuel, notwithstanding the fact that the moisture content of the dried fuel was much lower than that of the raw fuel. They attribute this “to the thorough washing to which the lignite is subjected.” Furthermore, Cooley and Lavine (5) found that the dehydration is accompanied by a collapse of the smaller cells in the woody constituents of the coal. This part of the present investigation, dealing with the effect of certain inorganic materials on the carbonization of steamdried lignite, was undertaken primarily because of these phenomena. An earlier study was made by Adams (I), working with Lavine and Mann a t the University of Minnesota, on the low-temperature carbonization of steam-dried lignite (without addition of inorganic salts), and the results did not differ greatly from those obtained with freshly mined lignite. I n general, it was found that the gas and tar yields were slightly less for the steam-dried fuel, whereas the char yield was increased slightly. No evidence of cementation or coking was obtained with the steam-dried fuels. TABLE111. EFFECTOF PARTICLE SIZE ON STRCCTURE OF LIGSITECOKEMIXTURE (142.5 grams lignite -PIRTICLE-SIZE
-20
-40
+ 35.52 grams AIClr6H,O + 28 grams water) > f I X T U R E B USED-
-60
EXPT.+40 +60 +80 % % %
+loo
-80
-100 +150
%
%
.. .,
-150
+Zoo
-200
% ..
%
1
50
15
10
2 3 4
50 30 30
15
30
..
30
10 10
., .. .. ..
,
..
5
40
15
5
5
5
5
50
.,
5
5
5
10
.
.. ..
.&PPE&RLNCE OF
COKE
Poor: cracked badlv: soft Very soft Fair; center very soft Badly cracked; crumbled easily 25 Few cracks, otherwise good: center soft 30 Badly cracked: center uncemented and soft 40 Hard b u t very badly cracked 20 Badly cracked: quite
25
35 20 30
5 LIGNITE 7 10 30 5 5 5 5 Lavine, Gauger, and Mann (IO)found that certain Dakota 8 5 35 10 10 10 10 lignites can be dehydrated with a minimum of disintegration soft, 9 40 16 6 5 5 5 23 Sin& horizontal crark; by the use of saturated steam a t elevated pressures. Cooley very hard: gray nietallic luster: appeared and Lavine (4)found that the more woody lignites are better well cemented under suited for this process and that the deposit from Wilton, K’. microscope Dak., gave the best results. VELVASTEBM-DRIED LIGNITE. The T.’elva steam-dried One of the characteristics of the steam-drying process is that the increase in ash content is not in proportion to the lignite chars, for each salt added, had practically the same reduction in the moisture content of the lignite. Lavine, physical appearance as was evidenced with the corresponding Gauger, and Mann (IO) found that in many cases the dried chars from the freshly mined lignite with the single exception 6
STEdM-DRIED
TURE
CARBOXIZATIOS DAT4
H2 %
CO
ClHs
CH4
Nz
-20 +40
-40 +60
-60 +ZOO
%
%
%
%
%
%
%
%
7.1 8.0 2.8 7.2 5.2 6.2 9.2 8.1
3.3 1.5 2.4 2.1 2.0 3.0
4.0 1.8 6.2 2.8 5.5 5.4 0.8
2.0 7.6 0.2 5.8 4.0 7.0 6.8 3.8
30.6 45.2
22.1 22.1 Coherent 21.1 19.2 Coherent 22.1 25.3
26.5 18,s residue 25.5 24.4 residue 18.3 23.3
20.8 13.9
5.7
24.8 24.7 20.6 25.1 26.5 23.8 24.: 24.t
5.2 3.6
5.2 9.0
10.9 6.2
26.3 18.9
0.3 si. 8
33.6
i :3 5.4
1.5
4.6 3.3
23.4 17.0
7.0 0.0
34.2 23.6 25.0 17.2 Semi-coherent vesidue
No apparent Cementation or coking. disintegrated o n handling Very little cementation; outside h&d, inside soft; unlike other .ilt(SO‘)t chars
14.0 8.7 16.4 19.4 7.5
13.9 8.6
2.1
26.6 25.3 25.4 24.5 23.0 24.7 22.8
5.1 0.0 0.3 6 ,3 9.9 3.2, 15. I
34.8
20.5 Coherent 25.2 Coherent 31.9 17.5 41.5 20.1 Coherent
26.4 residue 27,O residue 21.6 24.4 residue
No cementation‘ diaintegrated on handling Hard residue; ciacked more t h a n Velva char: cementation ring not as large No apparent cementation: disintegrated on handling Hard residue; decided evidence of coking; unlike other iron chloride ohars No apparent cementation: soft: disintegrated on handling No apparent cementation; soft; disintegrated on handling Hard residue: decided evidence of coking
25.5 19.8 15.4 16.7 18.2 19.7 11.6
0.0 2.4 3.2, 1. 1.2 7.7 0.0
34.6 30.2 37.8 36.2 49.5
26.0 29.6 25.8 28.0 19 .,0 residue residue
1.5 7.6
1.1
7.1
18.2
10.5 7.4 15.2 11.9
10.6 14.0 16.6 9.8 12.9 9.5 6.8
9.8 7.0 8.4 9,7 5.1 10.2 9 6
11.I
2.0 1.3 3.7 9.7 5.2 2.5 1.1
0.7
2.3 4.6 3.0 6.1 3.8
,
29.5 32.4 47.1 35.6
-200
23.9 24.0 12.5 15.9
23.6 27,6 15.2 Coherent residue
35.4
22.1 14.9 18.4 17.8 26.3 Coherent Coherent
18 3 12 4 29 0 14.0 17.3 25.3 18.0 18,O 5.2
.kPPEARlSCE OF COKE
RESIDUE
No apparent cementation: disintegrated on handling
No apparent cementation; disintegrated on handling
Hard coke appearance. gray metallic luster No apparent cementadon; disintegrated o n handling No apparent cementation: disintegrated on handling Hard coke appearance N o apparent cementation No apparent cementation: disintegrated on handling
No apparent cementation or coking Best coke residue: very hard: gray metallic luster
No No No No No
evidence of coking. soft. disintegrated on handling apparent Cementation; ;oft: disintegrated on handling cementation. soft. disintegrated on handling apparent cer$entaiion: soft: disintegrated on handling apparent cementation: soft; disintegrated on handling Hard residue; softer t h a n for unprocessed lignite Hard residue: gray metallic luster: best of Velva ateam-dried ohars
gas, wliereas in the case of the Alz(S0,)s.18H,0 tlie decrease in tar is accompanied by an increase in char and a decrease in gas. A larger decrease in tar yield from steamdried Velva lignite than from raw Velva lignite is also brought about by MgCI&H,O. In this case the decrease is accompanied primarily by an inerense in char yield. I n the case of FeC1&H2O with raw Velva lignite the large decrease in tar yield is accompanied by an increase of some 14 per cent in gas yield and an increase of over 8 per cent in char yield. With steam-dried Velva l i g n i t e this sa.lt introduces a similar decrease in tar yield, but in this instance the decrease is acA B companied only hy an increase in char yield. The a.ction of the AlC13.F1110 is found also to be different. Thus, with the raw lignite this salt introduces a tar yield decrease of some 10 pcr cent nhich is accompanied by a large increase (18.7 per centj in gas yield and a mnch smaller (7.3 per cent) increase in char yield. With the steam-dried Velva lignite the salt causes a decrease of nearly 9 per cent in tar yield, but in this case the decrease is accompanied by a large decrease (16.7 per cent) in gas yield and a small increase (4.G per cent) in char yield. Seemingly, CaCOs causes a small increase in ttrr yield (2.7 per cent) with the steam-dried lignite, whereas with the raw lignite this sidt c D introduced 5 small d e c r e a s e in tar yield (2.6 F~~urn:2. C o ~ e Ps ~ ~ O AI~(SO&I8I~I~O M ( X 25) per cent). In the case of steam-dried l i g n i t e A . Raw Vclva iiqnite B . Aaid-ivsshed Velva Iixnite C. Steam-dried V e l v i ~lignite D . Steam-dried Wilton lignite the increase in tar is accompanied hv a decreaFe in gas yield (F.3 per cent) and-also hy an uf the AIC18.(iIIs0 elii~r. This salt did riot produce the incri:ase in char yield (2.6 per cent) I n the case of the raw marked effect that i t produced nit11 tlie freshly mined lignite coni the deerea,se in tar is accompanied by a relatively large in that the briquet mas crakcd badly, was much softer, and increase (17.9 per cent) in gas yield and a small increase in char yield (5.0 pcr cent). did not exhibit a gray metallic luster. These Pacts indicate that, in the presence of inorganic salts, The effect of steam-drying on the other produeds of carhonization can be determined readily by comparing results steam-drying reduces the extent of secondary decomposition for the raw Velva lignite with the results for the stean-dried of tar. This is based on the assumption that tlie increased gas yields arc due primarily to secondary deconiposition of Velva lignite (Table 11). The results for the blank runs (experiments 1 and 20) show tar &her than to a further gasification of the fuel. A contlrat steam-drying in itself introduces the following eiianges: sideration of the volatile matter contents of the chars for R Kiven salt from the raw and steam-dried Velva lignite shows Tho tar yield is deere:lsed approximately 50 per cent. The them to he approximately the same. It is probable, therev i i i i r arid gas yields %reaffected hut slightly. fore, that gasification has progressed to about the same extent The screen analyses of the cham &ow n somewhat 1:wgcr in the two cases and the increased gas yields with the raw :amount of cementation for the steam-dried char (blank). 'The carbon dioxide and ethane contents of the gas two lowcreil Velva lignite are due primarily to secondary decomposition sorrrewhat. Eonever, the cnrbon monoxide content is increased of the tar or to some other similar, hut unknown, reaction. from approximately 3.5 t o 10 per cent; the hydrogen content is The proximate analyses of the chars from steam-dried inei.e:ised from approxlmirtely 7 to 10 per cent. Velva lignite are given in Table 11. A comparison of these results nit.h the arinlyses of the chars from raw Velw lignite If corresponding salt chars are compared, the influence of shows the following: steam-drying in some cases is similar to that out.lined above; in other cases this influence is quite different. Thus, the low The volatile matter coutents for oorrcsimuding chars are ai>tar yield, as noLed in tlie tilank run, still persists in thc carboni- imxim&Iy the same aations in which the inorganic salts were added. The data in Table 11 slioiv that the tar yields in the cam of the raw Velva lignite varied from 2.14 to 3.48 grams per 100 grams of content is the srtmo in both cams. the moisture and asli-free lignite. In the case of steamThe AL(S04j,~lS13,0 char %-asfound to poasess a higher dried Velva lignite the yields of tar on a similar basis varied volatile matter and ash content than the other chars in from 1.19 to 1.89 grams. The influence of Ala(SO&18H;0 and Na2C01in reducing this series. Attention has been called previously to a similar the tar yield from steam-drird Velva lignite to a marked de- phenomenon with the aluminum sulfate char from raw Velva gree is especially noticeable. An inspection of the data for lignite. To determine whether this higher volatile content the steam-dried Velva lignite in Table I1 ~ J I O W S that with was real, it was decided to study the A1g(SOh18H90 char l\a2C03the decrease in tar is accompanied by an increase in Accordingly a sulfur balance was made with the char from,
I N D U S T R I A L k N D E N G I N E E R I N G C H E 41 I S T R Y
March, 1933
the blank steam-dried Velva run (experiment 20) and with the -&(S04)3.18Hz0char in this series (experiment 26). The total sulfur was determined in the char, in the residue obtained after a determination of volatile matter had been made, and in the ash of the char The results of this work are as follows:
Char Volatile matter residue Ash
SULFUR IN-
%
.41&301)~18H,Ochar %
0.36 0.32 0.33
9.2 '4.7 2.2
Blank char
A simple calculation shows that the total sulfur content of the char as given above corresponds to the quantity of sulfur added as Alz(S04)318H20 plus the inherent sulfur in the char. Evidently the aluminum salt is present as the sulfate rather than the oxide. The possibility exists that the sulfur content of this salt might be transferred to some other constituent in the coal by interaction with the aluminum sulfate during carbonization. This would allow the aluminum salt to revert to the oxide (or silicate?), and a t the same time the sulfur would be retained in one form or another. It is the opinion of the authors that the latter possibility seems remote. The above data show further that the high volatile matter content of the Alz(S04)3.18H20char is due probably to the partial decomposition of A12(SO& during the volatile matter deterniination and not to a less thorough gasification during the carbonization process. GAS. An inspection of the gas analysis data shows that the inorganic salts did not produce radical changes in the composition of the gas from steam-dried lignite It is seen that AlC13.6H?0 reduced the carbon dioxide from 48.8 t o 42.3 per cent, whereas A12(S0&.18H20 increased the carbon dioxide from 48.8 to 65.1 per cent. A similar phenomenon was noted in the carbonization of raw Velva lignite with these salts. The effect of steam-drying on the constituents of the gas can be determined by comparing these analyses with the analyses of the gas from raw Velva lignite. The general tendency of steam-drying is t o increase the hydrogen and carbon monoxide in the gas and to decrease the quantity of methane. This is made clearer from the following averages for the entire series: %
STEAM-DRIED V E L V A LIQNITE %
6.6 2.3 24.4
11.5 8.5 18.1
RAWVELVA LIQNITE Hz
co
CHI
333
The char yields from this lignite were approximately the same as obtained with the steam-dried Velva lignite. The Alz(S04)3.18H20yielded a slightly larger quantity of char than was obtained with the other salts. The tar yields, with exception of the CaC03 and M g C b 6H20, were less than obtained from the steam-dried Velva lignite. Furthermore, the influence of the salts investigated on the yield of tar from the Wilton lignite is quite different with this fuel than with the Velva lignite. Thus, Alz(SO&*18H20 does not introduce the large decrease in tar that was obtained with the Velva lignite; Na2C03 introduces a much smaller decrease than was obtained with the Velva lignite; the decrease with FeCb6H2Ois even more marked with the Wilton lignite; and CaC03 and MgC12.6H20 cause a very marked increase in tar yield amounting to 79.2 and 51.0 per cent, respectively. The analyses of the Wilton chars show the volatile matter percentages to correspond rather closely to the volatile matter contents of the steam-dried Velva chars. The ash contents are seen to differ because of the lower inherent ash content of the steam-dried Wilton lignite. The order of increasing ash content, however, is the same as with the raw and steamdried Velva chars. The gas from steam-dried Wilton lignite is characterized by a higher hydrogen, carbon monoxide, and methane content and lower carbon dioxide content. PHOTOMICROGRAPHS OF Alz(SOa)3.18H90COKES. Photomicrographs of flattened specimens of 8 1 2 (SO,) 3.18H20 cokes from raw, acid-washed, and steam-dried Velva lignite, and from steam-dried Wilton lignite are shown in Figure 2. The specimens were prepared for photographing under the microscope by first flattening the surface with fine emery cloth and then removing dust particles by washing with water. The surface was dried before photographing. The well-cemented appearance of these cokes is evident. The rather homogeneous structure of the acid-washed coke (Figure 2B) is proof that further cementation of the coked particles was obtained in this case than with the other residues. a4CKNOWLEDGMEST
The authors are indebted to L. C. Harrington for his cooperation in making this study possible.
LITERATURE CITED (1) Adams, R., Master's Thesis, Univ. of Minn., June, 1931. (2) Bahr, H., Stahl u. Eisen, 44,1, 39 (1924). (3) Bahr, H., and Fallbohmer, K . , Gas- u. Wasserfach, 69, 909, 929 (1926).
(4) Cooley, A. hl., and Lavine, I , Univ. of N. Dak., unpublished
STEAM-DRIED WILTON LIGNITE.The salts Ka2C03, CaCOs, and MgC12.EH20 produced chars with the steamdried Wilton lignite that in physical appearance were similar to the corresponding chars from raw and stearn-dried Velva lignite. However, the addition of FeC13.6H20t o the Wilton lignite produced a coherent psuedocoke unlike that of any of the other FeC13.6H20residues. In this case the residue was coherent, did not crumble upon being handled, and exhibited coking and cementation to a marked extent. Furthermore, this pseudocoke was considerably better than the one produced by the addition of A1C13.6H20 to the Wilton coal, a phenomenon just opposite t o that obtained with the ram and steam-dried Velva lignites. The Alz(S04)3.18H20 char from the Wilton lignite was coherent but did not possess the hardness nor the well-cemented appearance under the microscope that corresponding residues from Velva lignite exhibited.
rept., 1932. (5) Cooley, A. bl., and Lavine, I., Univ. of N. Dak., unpublished
rept., 1932. (6) Fischer, F., and Lessing, R., "Conversion of Coal into Oil," Van Nostrand, 1925. ( 7 ) Gauger, A. W., and Salley, D., Proc. Intern. Conf. Bitz~minous Coal, 2nd Conf., 1, 312 (1928). (8) Gordon, M., Lavine, I., and Harrington, L. C., IND.ENG.
CHEM.,24,925 (1932). (9) Koth, A. W., and Lavine, I., Univ. of N. Dak., unpublished reDt.. 1932. (10) Lavine, I., Gauger, 8.W., and Mann, A., IND. ENG.CHmf., 22, 1347 (1930). (11) Sutcliffe, J. A., and Cobb, J. W., Fuel, 6, 449 (1927).
c.
RECEIV~ August D 22, 1932. Presented before the Division of Gas and Fuel Chemistry at the 84th Meeting of the American Chemical Society, Denver, Colo, August 22 t o 26. 1932. This paper is part of a thesis by A. W . Koth, submitted in partial fulfilment of the requirements for the degree of master of science in chemical engineering. University of North Dakota. July, 1932.
