INDUSTRIAL AhTD ENGINEERING CHE-VISTRY
March, 1929
239
Relation between Caking and Moisture- Absorbing P o w e r of Some Japanese Coals' Sadao Iki M E I J I COLLEGE O F
TECHNOLOGY. TOBAIA, FEKUOKAKEN, JAPAN
HE water content of coal varies according t o the conditions under which it is mined and its subsequent treatment. However, after exposure to the air the moisture content becomes nearly constant for a given coal. This subject of moisture in coal is very important commercially as well as in scientific studies of coal. For example, the usual indirect method for the determination of moisture2may give errors due to evolution of occluded gases, oxidation of the coal, or reabsorption of moisture during cooling and weighing. Several other methods have been proposed, but each has its disadvantages. The moisture content of coal is influenced by the humidity of the atmosphere3 in which it is exposed. The water in coal is present for the most part as moisture.' A small proportion, however, is present in the combined state but the nature of the combination has not yet been fully revealed. Furthermore, the moisture in coal depends largely on the quality of the coal and this is also still a matter of discussion. I n the course of an investigation of the caking property and oxidation of coal the author has found a close relationship between caking and moisture-absorbing power of some Japanese coals. These studies will be described briefly.
T
Preliminary Treatment of Coals
Japanese bituminous coals of different caking properties were used in these experiments, with a few anthracites and brown coals for comparison. They were stored under water in a tank to prevent oxidation. Before use they were crushed and sieved t o a definite fineness with standard sieves (Institute of Mining and Metallurgy) and left to stand in a closed vessel containing sulfuric acid of a definite concentration in order to keep the atmosphere around the samples a t a constant humidity.
Analysis and Determination of Caking Power
The analyses of the coals were made by the usual methods. The caking power was determined by observing the coke buttons after the volatile matter determination and also by the modified Campredons and Lessing6 methods. The results (Table I and Figure 1) show that the moisture content decreases with the caking power. To learn whether this tendency is accidental the following experiments were conducted. Variation of Moisture i n Coal with Humidity
Inasmuch as the moisture in coal is influenced by the humidity of the atmosphere in which it is exposed, the samples were kept in a closed vessel containing a 40 per cent sulfuric acid solution. This concentration shows a relative humidity of 58 per cent and the small change in temperature has little effect on it. The effect of the change of temperature and humidity of the atmosphere on the weight of coals, both in and out of this vessel, was determined. Table I1 and Figure 2 show that the constant-humidity vessel is fairly effective in keeping the moisture content of the samples constant, and also that change of humidity has the greatest effect with high-moisture and low-caking coals. Relation between Caking and Moisture-Absorbing Power
Seven samples of coals having different caking powers were selected and their moisture-absorbing powers were determined by placing the dried samples in the constant-humidity vessel 8 Gray, Fuel, 2, 42 (1923): Meurice, Ibid., 2, 305 (1923); Deville, Ibid., 2, 293, 345 (1923). 6 Ibid., 2, 188 (1923).
Received August 8, 1928. 8th Intern. Cong. Appl. Chem., 1912; Huntley and Coste. J . SOC.Chem. I n d . , 32, 62 (1913). Moore and Sinnat, J . Chem. SOC.,123, 275 (1923); J . SOC.Chem. Ind., 44, 200T (1926). 6 Porter and Ralston, Bur. Mines, Tech. Paper 113. 1
* Rept.
*
Figure 1-Relation
between Proximate Analysis and Caking Power
Figure 2-Variation
of Moisture by Varying Humidity
IATDI;STRIAL A S D EXGINEERING CHEMIXTRY
240
0,ow I 0
I
I
s
10
I
/s
1 40
I
29
1
30
I
3s
I
ro
I J 9s
qoo
T m e o f f h i p r u i e (hrs)
Figure 3-Relation
I
0
I f
I
I
10
15
Figure &Relation
The relative moisture-absorbing powers of the different kinds of coal samples of an anthracite, two bituminous, and three brown coals were then determined by the method used in the previous tests. The results (Figure 4) show that the lower rank coal has remarkable affinity for moisture. Table I-Analysis
Moisture
COAL
2
Yiibari
72
1
1
96
/?o
/W
between Rank of Coal a n d MoistureAbsorbing Power
The preceding experiments indicated that moisture absorption depends on the properties and consequently on the constitution of the coal. Therefore, the coal was separated by means of pyridine and chloroform into alpha, beta, and gamma, and the ulmin was extracted from brown coal with potassium hydroxide solution. The moisture-absorbing
of Coals a n d Determination of Caking Power
PROXIMATE ANALYSISVolatile matter Fixed carbon
Ash
CAKING HEIGHT INDEX OFCOKE (MODIFIED USCAMPREDON)SING) SULFUR NITROGEN
Cm.
%
%
70
0.31
8.18
3.31
0.91
50
0.54
6.61
0.30
1.42
50
5.0 2.0
%
Bituminous coal: 1 Miike
1 $8
Moisture-Absorbing Power of Various Constituents of Coals
7---
SAMPLE
1 -Z$
~me?&~xposuie(hrs)
b e t w e e n Caking Power a n d Moisture Absorption
described above and measuring the weight increase due to moisture absorption. The results (Figure 3) show a distinct relationship between caking power and moisture absorption. Relation between Rank of Coal and Moisture Absorption
Vol. 21, No. 3
%
%
5.0
3
Takashima A
1.25
6.82
0.57
1.41
43
4
Takashima B
1.06
4.08
0.34
1.42
44
4.5
0.87
1.24
42
5.0
0.52
1.19
42
5.0
0.26
1.54
41
3.8
1.51
38
3.0
5 6 7
Takashima C Takashima D Takashima
E
9.29
1.65
8.39
1.78
2.97
1.17
8
Hashima A
1.44
4.57
0.52
9
Hashima B
1.27
4.71
0.35
1.38
35
3.2
1.36
7.16
2.13
0.92
28
2.0
1.26
4.78
0.77
1.00
28
1.5
1.75
4.68
0.32
0.91
15
1.3
1.62
12.37
0.46
0.82
11
1.9
2.17
7.12
0.29
0.88
10
1.4
1.90
5.91
0.34
0.92
9
1.3
1.89
4.64
1.46
0.93
5
1.4
2.02.
18.08
0.52
0.85
8
1.1
1.74
8.19
0.97
0.92
6
1.6
Akaike D
1.96
8.95
0.36
0.95
6
1.4
20
H6koku A
2.72
6.14
0.32
0.95
6
0.9
21
H6koku B
2.39
6.05
0.37
0.88
5
1.4
22
H6koku C
2.56
17.83
0.30
0.84
0
1.35
23
H6koku D
2.41
10.29
0.68
0.82
0
1.0
10 11 12 13 14 15 16 17 18 19
Matsushima A Matsushima B Meiji A Meiji B Meiji C Meiji D Akaike A Akaike B Akaike C
Anthracite coal: 3.85 8.17 85.94 24 Heij6 1.50 Brown coals: 15.91 Higashimisome 8.90 48.55 26.64 25 14.97 35.34 45.16 4.56 Ibaraki 26 16.70 37.54 26.48 19.28 Chita 27 14.10 20.32 28 Yamagata 30.78 34.80 The figures in parentheses represent the proximate analysis as (moisture volatile matter fixed carbon
.
+
+
100.00).
I,VDUSTRIAL A N D ESGIA7EERI,YG CHEMISTRY
March, 1929
TIMEEXPOSED Days 1
Table 11-Change of Weight of Coals i n a n d o u t of C o n s t a n t - H u m i d i t y Vessel (Sample taken, 1 gram; fineness of sample, 30 to 50 mesh) TEMP. OUT HUMIDITY OUT CHANGEOF WEIGHTIN VESSSL C H A N G E OF W E I G H T O U T OF Miike H6koku D Takashima E OF VESSEL OF VESSEL H6koku D Takashima E Gram Gram Gram Gram Gram c. %
2
3 4
M.
M. M. M. M.
A . M.
P. A. P. A. P.
5
8
M. M.
M. &I.
M.
9
A . M. P M.
10
12
M. 31. M. M. A. M.
15
P. M. A. M.
A. P. A. P.
11
P. M . A. M. P. 31.
16
+ O . 0008 -0.0012 ,0020
+o
7;-
+ O . 0006 0.0004 0.0002 +0.0006
-+0.0002 0.0008 + O . 0006 -+0.0004 0.0006 -10,0006 0.0005 -+ O0.0000 . 0004
-0.0014
+ O . 0006
-
0.0008 +0.0014
+ O . 0026
-0.0010 +0.0022 - 0,0008
- 0.0004
+0.0010
- 0.0014
+ O . 0004
+ O ,0018
- 0.0040
- 0.0003 - 0.0008 + O . 0006 - 0.0002
-
+o.0.0000 0002
+ O . 0004
+ O . 0036
-0.0030 +0.0038 -0.0015
1
I
lo
16
,
Figure 5-Moisture
...... - 0.0002 -
0.0006 +0.0022 0.0020
I
I
I
I
I
I
I
1
I
I
98
72.
91
I20
I
0.01
1
%
I
l
o ot
0
Miike Gram
-
- 0.0106
1
QOO
VESSEL
......
......
25 25.5 21 26 21 26 21.5 30 22 26.5 23 30.5 24.5 28 24.5 28 24 29.5 24 2s 24 2s 23 27
A. M. P. A. P. A. P.
24 1
G.00
I ~~~e
*n hours
Absorption of Various Constituents of Coals
I
5
/#Y
I fo C+
Figure 6-Variation
I -% +owe
I %
1 72
(4~5)
I 96
I
I
1
IZU
/FF
l6B
1 /92
of Moisture Absorption of Coal b y Weathering
Effect of Weathering on Moisture Absorption
It had been pointed out by Dennstedt and Bunz7 that the weathering of coal increases its moisture content and that this is due to the formation of ulmin during weathering. The writer’s results (Figure 6) confirmed this finding. Therefore, this seems to be a good means of measuring the degree of weathering of bituminous coals. Summary
The foregoing experiments show that the chief caking constituent of coal, gamma, has the least moisture-absorbing power and that the strongest absorbing constituent is ulmin. This may be the reason why moisture-absorbing power decreases with increase of caking power and why low-rank coal and weathered coal have a strong affinity for moisture. Figure 7 shows the relation between solvent analysis, caking power, and moisture content of coals. 7
Figure 7-Relation
Dennstedt and B u m , 2. angew. Chem , 21, 1825 (1908).
between Solvent Analysis, Caking Power, a n d Moisture
power of each of these constituents was then determined. The results (Figure 5 ) show that ulmin has the greatest moisture-absorbing capacity, alpha and beta medium, and gamma the least. The coals of high caking power have high gamma content, and the lower rank coals contain a large amount of ulmin. These facts seem to explain the relation between caking power and moisture absorption of coals.
Chemistry and the Cocoa and Chocolate Industry-Correction In our article under this title, IND. ENG.CHEM.,20,1295 (1928), the work of Bainbridge and Davies on the aroma of chocolate, to which reference was made in the third paragraph of the second column, was performed in the laboratories of Rowntree Company, of York, England, instead of Cadbury’s as reported. FRANK C. GEPHART
