Significance of Solvent Extraction and Rational Analysis in Coal Carbonization Reproducibility of Analytical Results E. B. KESTER,~ E. J. SCHNEIDER, AND F. W. JUNG,Pittsburgh Pittsburgh, Pa.
F
OR a number of years considerable attention has been given to the resolution of coal by means of solvents. That the coking principle is related to the extractable matter in coal is unquestionably true, as it is possible to deprive a coal of its coking powers by solvent action and to restore them to a degree by reincorporating the extract. The exact nature of the relationship, however, is still but poorly understood. Hypotheses have been made and apparently substantiated, only to be destroyed later by conflicting evidence. Recently the use of rational analysis has been emphasized by Francis (11)as an aid to determining the field of usefulness for a particular coal, but this view is disputed by Roberts (14). At the time the Pittsburgh Experiment Station of the United States Bureau of Mines undertook a survey of the gas-, coke-, and by-product-making properties of American coals, it was decided to include among the many tests and analytical procedures to be investigated an assay of the bituminous material extractable by benzene under pressure (10) including a separation into oily and solid bitumens, a resolution of the coal into its alpha, beta, and gamma constituents according to Wheeler ( I S , 16), and an analysis of the so-called rational constituents of coal-namely, the total bitumens, ulmins, and resistant plant residues (1.2). The end in view was the establishment, if possible, of some quantitative relationships between the amounts of such extracts or “rational” ingredients and the gas-, coke-, and byproduct-making properties of the coal or other functions of the coal numerically expressible. Attempt has been made to carry out these extractions and separations according to procedures that would reduce variables to a minimum. Twenty coals (Table I) were studied exhaustively and data compiled for a comparison with such properties as ultimate and proximate analysis, behavior on carbonization, and yields and properties of the coke and by-products. To complete 1 Present
address, Mellon Institute of Industrial Researoh, Pittsburgh,
Pa.
Experiment Station,
U. S. Bureau of Mines,
the comparison, certain specimens were resampled and reanalyzed to ascertain the duplicability of these tests. Split samples have been analyzed by different laboratories to see if the personal equation is significant in this type of analysis.
ALPHA,BETA,AND GAMMA DETERMINATION The resolution of coal into alpha, beta, and gamma constituents after Wheeler (IS,16) involves the extraction of coal in a Soxhlet apparatus with pyridine over a period of days, the isolation of the pyridine extract which is made up of both beta and gamma constituents, and the separation of these two by another Soxhlet extraction with chloroform. Table I1 summarizes the analyses for these constituents as well as the values for bitumens, ulmins, and resistant residues. The operations for separating coal into alpha, beta, and gamma constituents, simple though they may appear superficially, present difficulties. Coals vary, for example, in the length of time required to extract them fully. Some give up their soluble matter quickly; others require long periods. Ground coal in a paper Soxhlet thimble tends to swell and even tear it apart, provided an inert diluent is not used. The particles may disintegrate under the action of pyridine or may become extremely friable. At any rate, indications are that the penetration by pyridine is extremely deep. The chief drawback to the pyridine extraction is the difficulty of obtaining check results on split samples, despite every effort to inhibit oxidation and to insure uniformity in the conditions, as has been repeatedly observed by every worker who has attempted pyridine extraction of coal. The chloroform extraction of the pyridine extract proceeds with greater ease and with less variability in the amount of material separated. PROCEDURE. As the technic of the alpha, beta, and gamma determination became better standardized and as improvements were incorporated into the Soxhlet apparatus, it was found possible to obtain closer checks than in the preliminary tests.
TABLEI. DESCRIPTION AND ANALYSES OF COALS
COAL NO.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
STATE
COUNTY
BED
MIHE
Pennsylvania Allegheny Ocean No. 2 Kentucky Letoher No. 204 Virginia Roda No. 3 Wise Maryland Arnold Garrett 60 per cent No. 4; 40 per cent N 0. 1 20 er cent No. 4 ; 80 per cent N 0. 1 Alagama Jefferson Flat Top Alabama Jefferson Flat Top Pennsylvania Fayette Edenborn Illinois Franklin Orient No. 1 Michel British Columbia Allison Fayette Pennsylvania Empire Walker Alabama Boone No. 2 Logan W. Virginia W. Virginia Xanawha Point Lick No. 4 W. Virginia Spruce River No. 4 Boone Alabama Wylam No. 8 Jefferson Alabama Wylam No. 8 Jefferson Columbia Carbon Utah Wildwood Pennsylvania Allegheny
Pittsburgh Elkhorn Taggart Davis
PROXIMATS ANALYSIB. MOISULTIMATE ANALYSIS, ‘MOISTUREAND T U R W AND ASH-FREE ASH-FREE oxyVolatile Fixed Hydrogen Carbon Nitrogen gen Sulfur matter carbon % % % % % % %
Mary Lee (unwashed) Mary Lee (washed) Pittsburgh No. 6 Nos. 2 and 3 Pittsburgh Black Creek Chilton No. 2 gas Alma Pratt unwashed) Pratt [washed) Lower Sunnyside Thick Freeport
98
6.6 6.1 6.0 5.4
84.6 84.6 86.3 87.5
1.7 1.6 1.6 1.7
7.0 7.1 5.5 3.7
5.4 5.3 5.5 5.3 5.1 5.7 5.7 5.5 5.6 5.7 5.4 5.5 5.8 5.7
86.2 87.1 85.5 €42.2 87.4 85.1 84.0 84.8 84.2 84.5 86.4 86.8 81.5 84.0
1.8 1.8 1.8 1.7 1.4 1.8 1.9 1.7 1.5 1.6 1.8 1.8 1.7 1.7
5.7 4.9 6.1 9.8 5.5 6.0 7.2 7.4 7.8 6.3 5.7 5.3 9.9 7.2
1.1
0.6
0.6 1.7 0.9 0.9 1.1
1.0
0.6 1.4 1.2 0.6 0.9 1.9 0.8 0.6 1.1 1.4
36.7 38.3 37.8 24.9
63.3 61.7 62.2 75.1
33.6 31.5 37.1 40.3 29.2 37.1 38.2 38.7 40.6 41.5 33.7 33.6 43.4 39.6
66.4 68.5 62.9 59.7 70.8 62.9 61.8 61.3 59.4 68.5 66.3 66.4 56.6 60.4
March 15, 1934
INDUSTRIAL AND ENGINEERING CHEMISTRY
99
TABLE11. RESULTSOF EXTRACTION WITH SOLVENTS AND RATIONAL ANALYSES.(Ash-free dry basis, original samples) COAL
No. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
BED Pittsburgh, Ocean No. 2 (unpublished) Elkhorn (unpublished) Taggart Roda (3) Davis dpper Freeport (1) Blend'of 80 per cent Pittsburgh and 20 per cent Davis coals Blend of 60 per cent Davis and 40 per cent Pittsburgh coals Mary Lee (unwashed, 4) Mary Lee washed 4 ) Edenborn hittsbuigh 5) No. 6 (Frknklin Co., I6., 6) No. 3 (Michel, B. C., 2 ) Allison Pittsburgh ( 8 ) Black breek (7) Chilton (81 No. 2 gas ( 9 ) Alma (unpublished) Pratt (unwashed un ublished) Pratt (washed & uilished) Lower Sunnydde ?unpublished) Thick Freeport (unpublished)
A representative laboratory sample of the coal is ground to
pass a 60-mesh sieve and dried for 1 hour a t 105",C. One to 1.5 grams are mixed with 4 or 5 volumes of clean quartz sand in an
alundum Soxhlet thimble and extracted with 125 cc. of pure pyridine in an atmosphere of dry nitrogen. The major portion of soluble material is removed in 4 to 6 hours, but appreciable additional amounts are often obtained up to 72 hours. This is the minimum time allowed regardless of the rapidity of the extraction and usually is sufficient for the typically bituminous coals. When coals difficult to extract are encountered, as is evidenced by the persistence of color in the descending solvent, an even longer time may be required. In general, the extraction is continued 24 hours after the descending solvent has turned colorless. Beyond this point, an additional 24 hours' extraction, as a rule, removes only slight amounts (0.2 to 0.3 per cent) of soluble material. The type of Soxhlet best adapted to this extraction is one equipped with standard ground-glass joints. In the event of breakage any part can be replaced readily from stock; furthermore, a goose-neck can be constructed from standard joints for use in distilling off the pyridine from the extract a t the end of the operation. Thus, cork and rubber connections, which are attacked appreciably by pyridine, are eliminated. Dry nitrogen is admitted to the apparatus in a slow stream through a capillary side arm sealed to the extraction flask well above the surface of the boiling liquid. Between the tank and drying tower, a rubber gas-storage bulb, such as is used in an Orsat atmaratus. is inserted on a T-connection, to maintain a steady &w of gas at all times. From the top of the condenser, nitrogen is allowed to escape through a sulfuric acid seal so construtted that when the Soxhlet spills, a sufficient volume of acid rises into a reservoir to compensate for the partial vacuum created. During the initial part of the extraction, the Soxhlet should be run slowly, about one spill every 10 or 15 minutes, to prevent the alundum thimble, which does not drain very rapidly during the first hour, from overflowing. Subsequently, the operation may be speeded up until the spills occur every 5 to 7 minutes, provided the porosity of the thimble is not too fine. After the first 7 or 8 hours of extraction, it is advisable to substitute fresh pyridine, as protracted boiling of the somewhat concentrated solution of coal extract tends to polymerize it in part, and a t the end of 48 hours the solvent should be changed again for the same reason. After 24 hours' extraction with the third increment if the color of the solution is of deep orange or darker, it is advisable to continue the extraction for another 24 hours. Meanwhile the accumulated fractions are set away, tightly stoppered, in a single container. The combined solutions of beta and gamma compounds are concentrated to a small volume (10 or 15 cc.) on a sand or mineraloil bath and then poured slowly, with stirring, into a beaker containing 200 to 300 cc. of dilute hydrochloric acid to remove remaining pyridine. A quantitative transfer is accomplished by carefully washing the flask two or three times with a little fresh pyridine. The mixture is then heated to boiling and allowed to cool before filtering through a tared filter crucible with an integral porous bottom of fritted glass. The filtrate is discarded. The residue in the form of a sticky cake is carefully triturated in the crucible with distilled water by means of a rubber policeman. To avoid the formation of lumps, which will not otherwise disDerse. the water is added a little a t a time until the mixture has acquired the consistency of thin batter. The mixture is washed back into the beaker by means of a stream of water from a wash bottle, heated to boiling, and filtered as before through the same crucible. This operation is
RESISTANT GAMMABITUMENS ULMINS R~SIDUES % % % %
ALPHA %
BETA %
63; 9 68.6 71.1 93.7
18; 8 17.5 17.6 2.1
17.3 13.9 11.3 4.2
11:9 10.0 11.0 9.4
82.1 84.6 79.5 84.9
6.10 5.5 9.5 5.7
26:7 15.0 26.5 19.3 14.7 20.0 15.3 17.3 14.6 15.8 14.3 15.0 15.2 20.4
ii:3 19.3 11.3 7.4 11.8 16.0 9.6 14.3 10.4 13.2 16.8 15.0 11.3 10.7
16:2 11.2 14.3 6.3 8.9 13.9 9.9 11.7 11.0 14.8 13.8 12.5 11.3 12.5
69: 5 77.6 76.9 87.5 82.2 69.7 71.3 70.3 78.5 75.2 73.7 79.5 74.9 70.7
1413 11.2 8.8 6.2 8.9 16.4 18.8 18.0 10.5 10.0 12.6 8.0 13.8 16.7
*.
*.
62:O 65.7 62.2 73.3 72.5 64.0 75.1 68.4 75.0 71.0 68.9 70.0 73.6 69.8
..
..
..
..
repeated once again and the crucible dried for 12 hours in a vacuum over sulfuric acid. It is then weighed. By subtracting the tare of the crucibles the weight of beta and gamma constituents is obtained. The dry cake is crushed to a powder with a stirring rod and as much of it as possible transferred t o a paper Soxhlet thimble. The remainder of the beta and gamma compounds adhering to the sides and bottom of the crucible is transferred almost quantitatively by repeated washing with small increments of chloroform, scrubbing with a policeman, and pouring the mixture through the thimble already in position in the extractor. Finally warm chloroform is passed through the disk by suction or by blowing to remove any gamma compound which may have found its way into the pores. In all 100 to 125 cc. of chloroform are used. (The extraction is carried out in an atmosphere of nitrogen exactly as in the case of the pyridine, until no further coloration is produced in the descending solvent.) After the first 7 or 8 hours the extraction is continued with fresh chloroform and after 12 or 24 hours with a third quantity of fresh chloroform. This is repeated until the solution after 8 hours is only slightly colored. The speed of extraction is maintained at a considerably higher rate than with pyridine. The combined solutions are evaporated from the previously tared extraction flask to a small volume on the water bath, 10 cc. of petroleum ether are added, very carefully evaporated to dryness, and the final traces of solvent are removed by reducing the pressure with a water pump. TABLE 111. DEVIATIONS FROM MEAN COALNo.
ALPHA
BETA
%
%
1
2 3 4 7 8 9 10 11 12 13 14 15 16 17 18 19 20 s-3 9-4 s-5 S-6
5-7 5-8 s-9 s-10
Av.
0.50 0.65 0.30 0.65 0.35 0.00 0.75 0.45 1.05 0.85 0.80 0.00 0.40 0.40
0.30
0.05 0.70 0.55 0.35 0.15 0.45 0.55 0.10 0.75 0.80 0.70 0.35 0.25 0.42
GAMMA
%
0.25 0.30 0.27 0.35 0.15 0.40 0.62 0.40 0.35 0.20 0.20 0.20 0.10 0.55 0.05 0.25 0.30 0.20 0.45 0.20 0.35 0.30 0.05 0.10 0.35 0.15 0.27
The weight of residue after thorough drying represents the amount of gamma compounds and is subtracted from the sum of the beta and gamma previously obtained; the difference, minus the ash content of the beta compounds, gives the amount of beta comDounds in the original coal sample. The gamma group contains virtually no ash. Calculations of the true percentages of beta and gamma groups are based Won the ash-free dry coal. The alpha group is determined by the
100
ANALYTICAL EDITION
difference between 100 and the sum of the beta and gamma groups. Table I11 brings out the deviations from the mean of 26 duplicate determinations, which were in most cases run side by side. It will be noted that the deviations from the mean, particularly of the alpha, vary within wide limits. For sample S-3 we find a 0 deviation but for S-6 a value of 1.05. S-7 also has a high one, 0.85. The same is true of the beta, where it is even more significant because of the relatively small quantities, compared with the alpha. Here we find two with deviations from the mean of 0.85 per cent (8 and 11) and one of 0.8 (5-7). The gamma apparently checks out a little better, the maximum being 0.62 (9) and the next highest, 0.55 (16).
BENZENE-PRESSURE EXTRACTION The benzene-pressure extraction has been carried out in a Fischer-type apparatus (IO) a t a temperature of 280’ C.and a pressure of 43 atmospheres. (The critical temperature and pressure of benzene are 288.5” C. and 47.7 atmospheres, respectively.) Coal is extracted repeatedly under these conditions until the increment of extract amounts to less than 0.3 per cent of the coal substance. The cooled benzene solution is filtered (to remove precipitated bitumens), and the filtrate is distilled to remove benzene. The residual matter is separated into oily and solid bitumens by dissolving 5 grams in 15 cc. of benzene and stirring into 50 cc. of petroleum ether. The precipitate formed is termed “solid bitumens” and the dissolved substance, “oily bitumens.” In this paper no consideration will be given to the role of the oily and solid bitumens individually but only to the bitumens as a whole, in relation to other critical data on the respective coals. Table I1 lists the total bitumen content of the coals studied. The duplicability of this determination is brought out by Table IV, which lists the deviation from the mean for 12 coal samples on which duplicate determinations were made.
Vol. 6 , No. 2
Ulmins were obtained by oxidizing the bitumen-free coal for a specific time with various strengths of dilute nitric acid containing (or not containing) potassium chlorate. The detailed procedure follows: The residual coal from the benzene-pressure extraction is either air-dried for several hours or heated at 105”C.under a high vacuum for 2 or 3 hours to remove the excess benzene, and then ground to pass a 20-mesh sieve. A 10- or 15-gram representative sample is taken and ground further to pass a 150-mesh sieve. During this process the coal is screened frequently to avoid an excessive formation of fines. The fines are not discarded. The specimen is then heated at 105”C. to constant weight. Three or four 0.5-gram samples of the treated coal are refluxed 7 hours with such of the oxidizing solutions in Table V as are in the vicinity of the one recommended for a coal of its rank. On cooling, each is filtered through a filter-crucible (tared at the end of the analysis rather than prior to the analysis because of the loss in weight caused by the caustic potash) with an integral porous bottom of fritted glass and washed well with cold water. The pores of the disks should be very fine to minimize the possibility of finely divided solid material passing through. This detail is especially important at a later stage of the analysis when the residues are being separated from the caustic humate solutions. TABLEV. OXIDIZING SOLUTIONS CARBON CONT~NT OF COAL, MOISTUREAND ASH-FREEBASIS N HNOa CC
78 79 80 81 82 83 84 85 86 87 88 89 90 91
.
37.5 40 42.5 45 47.5 50 46 and
....
..
.. ..
....
OXIDIZINQ SOLUTIONS Water
2 N “Os Cc.
.. .. .. ..
cc.
KClOa Grams
.. ..
4 28 29 30 32.5 35 40 50
The residue from one sample is washed from the crucible into an Erlenmeyer flask by 100 cc. of distilled water. Twenty cubic centimeters of N potassium hydroxide are added and the TABLEIV. DEVIATIONS FROM THE MEAN,BENZENE-PRESSURE mixture is refluxed gently for 1.25 hours, during which time the EXTRACT regenerated humic acids go into solution as potassium humates. COALNo. DEVIATION The refluxed mixture is centrifuged for 10 minutes in thick% .” walled 250-cc. Pyrex glass bottles, especially ada ted for this 0.2 7 purpose to throw down all fine1 suspended matter t&atotherwise 0.3 14 0.35 15 would hinder the filtration. 1 s much as possible of the super0.2 16 natant liquid is siphoned off very slowly through the same fritted 0.5 17 glass crucible as was used above, and the remaining liquid con0.25 s-9 0.3 taining more or less sludge is decanted into a small beaker and 19 0.0 9.3 set aside to be filtered later. The solid cake remaining in the 0.05 20 thick-walled bottle is returned t o the Erlenmeyer flask, treated 0.45 21 0.25 22 with an additional 50-cc. portion of 1 p-r cent potassium hydrox0.1 22a ide, heated to the boiling temperature for 0.5 hour, and the 0.25 Av process of separating solid material from the solution is repeated. The sludges from both the first and second treatments now are The average deviation, 0.25, is almost identical with the united and filtered, after which the total residual matter is average deviation for the gamma, and, the authors think, washed into a beaker with distilled water. represents a fair duplicability for this type of analysis. The The correct degree of oxidation is determined microscopilargest variation is 0.45 (sample 21). cally. An over-oxidized coal will be manifest by a more or less frayed and bleached condition of the spores and cuticular ULMINB AND RESISTANT RESIDUES matter. An underoxidized sample will contain masses of The residual coal from the benzene-pressure extraction was dark humic matter. For this reason i t is necessary for the used to obtain the relative proportion of ulmins and resistant operator to judge carefully between them and select that residues. In using this material the authors were slightly a t sample which has had the proper oxidation for the determinavariance with the Wheeler school (1.8)which recommends the tion. The mixture in the beaker representing the one thus residue from the pyridine extraction for this determination, selected accordingly is acidified with hydrochloric acid to but they adopted the procedure not without good reason, the expedite the filtration, brought to the boiling point, and filchief being the contamination of pyridine-extracted coal with tered through the same tared crucible used above. The residues are transferred quantitatively and washed with hot sand. Despite the heat treatment of the coal a t 280” C., the ul- water. Drying is carried out a t 105” C. for 1hour and then in mins were found quite as readily regeneratable to humic acids a desiccator over sulfuric acid or calcium chloride to constant as are the ulmins of a pyridine-treated coal, and furthermore, weight. The weight of residues thus obtained is calculated to the residual spores and cuticular matter are maintained in an a true value by determining the ash content. A8 the amount of residues necessarily is small, this determination requires the excellent state of preservation.
March 15, 1934
INDUSTRIAL AND ENGINEERING CHEMISTRY
use of semi-micromethods (20 to 40 mg.). Calculation of the residues to an ash-free dry basis is made by using the following equation: R =
- c)(l XU - a )
lOOy(1
- b)
where x = weight of dry sample (free of bitumens) y = weight of residue after extraction with alkali per cent of ash in coal before extraction with benzene a = 1- on -per cent bitumens of ash-containing coal b = 100 per cent of ash in residues e =
100
an additional procedure is followed. Four more determinations of residues are made in which each oxidizing solution employed contains exactly the proportion of potassium chlorate found to give the best degree of oxidation. The amounts of 2 N nitric acid, however, are varied. The residues after the alkali treatment subsequently are plotted against the corresponding‘volumes of nitric acid. If a sharp break occurs in the curve, the “heel” is selected (below which the curve is almost horizontal) as representing the point of complete ulmin regeneration. If a smooth curve results, resort must again be made to the microscope for selecting the proper point. The percentage of ulmin in the original coal, on the ashfree dry basis, is calculated by subtracting the sum of the bitumens and resistant plant residues from 100. The oxidations of the extracted coals usually were not run in duplicate on account of the number that were necessary to establish the curves. That a fair degree of duplication can be expected is learned from Table VI, which shows the amount of residual matter from an original sample and a resample obtained by treating each with identical amounts of oxidizing reagent and extracting the humic acids with alkali.
sample
Lower Sunnyside
Pittsburgh (Monongah)
C~./0.6-@. sample
%
%
l3:86 12.6
1214
40.0
ii:is
9.2
16:O 20.0 24.0 28.0 20.0 25.0 30.0 35.0
13.8 11.9 10.3
0:iS 0.35 0.35 0.35
25:O 30.0 35.0
0:0 0.0 0.0 0.0 0.5 0.5
...
...
si4 04
a$ ;Oil
11.3 10.1 14:o 12.9 12.3
11.1
9.7 8.5
1 1 8 2 0 1 7 1 2 9 16 7 k 18 d 4 IbCOAL1914 NUMBER I
I
I
I
I
I
I
I
I
I
FIGURE1. RELATION OF BITUMENS TO GAMMA At the conclusion of this study, four of the coals were resampled and independent solvent extraction tests and rational analyses carried out on the resamples. The results are shown in Table VII, together with the results on the original samples for comparison. The deviations, it will be noted, are somewhat larger than are obtained on split samples analyzed side by side (Tables I11 and IV). Moreover, the variations are not always in the same direction on proceeding from the original to the resample. Therefore it is not permissible to generalize on the effects of aging. TABLEVIII.
RATIONAL ANALYSIS BY Two DIFFERENT LABORATORIES
*.
Edenborn Mary Lee (washed) Orient
HYDRODEV~ACARBONS AND
LABORATORY Laboratory A U. 9. Bureau of Mines Laboratory A U. S. Bureau of Mines Laboratory A U. 8.Bureau of Mines Laboratory A U. S. Bureau of Mines
TION FROM
RESISTANT
RESINS’ MEAN RESIDUES ULMINS Less than 1 9S.4 0.6 5.5 92.8 1.7 0.55 5.0 88.4 6.5 0.0
6.5 5.0 7.0
1.0
5.5 5.6
0.05
8.6 7.8
84.9 93.0 85.2 90.5 84.5
2.0
4.0 9.9 0.4 a Material extracted by refluxing sample with pyridine and extracting pyridine extract with ether.
AV.
9:0 7.1 7.7 0.5 6.7 7.3 0.6 40.0 6.6 6.9 Average deviation from mean of 10 pairs of oxidation residues from original samplea and reaamples, 0.49. 0.5
E& *
Davis
(Oxidation of original and resamples) OXIDIZINQMIXTURE RESIDUES 2N FROM RESIDUES Potassium nitric ORIQINAL FROM chlorate acid SAMPLE RESAMPLE
Pratt
E 20
$@16
COAL
TABLE VI. REGENERATION OF HUMIC ACIDS
GJ0.6-8.
The average deviation from the mean of 0.49, of course, is obtained not from a series of duplicate determinations but from pairs made up of an original and a resample and hence is the result not only of experimental error but also of aging effects on the resample and possible sampling errors. It is seen that the deviation is not consistently of the same sign. The residual matter from the resamples of the Lower Sunnyside and Monongah seem to be higher than for the original samples but vice versa for the Pratt.
4 1 2
If the microscopic examination leaves some room for doubt,
COAL
101
An attempt was made to bring out the duplicability of the solvent and rational analysis by two laboratories. The authors succeeded in interesting another laboratory to the extent of carrying out a rational analysis on four split samples under fixed conditions, but have not done so on the alpha, beta, and gamma separations nor the benzene-pressure extraction. The results are listed in Table VIII. Except in the case of the Davis, a most difficultly extractable coal, the agreement for hydrocarbons and resins is fair.
TABLEVII. SOLVENT EXTRACTION AND RATIONAL ANALYSIS (Original and resamples) SAMPLE Sunnyside Thick Freeport Pratt Pittsburgh (Monongah)
DATEOF SAMPLINQ Original 4-15-32 Resampie, 8-26-32 Original 6-22-32 Resampie, 8-26-32 Original 2-4-32 Resampfe, 11-10-32 Original 11-16-32 Resampie, 12-23-32
ALPHA 73.65 75.2 69.8 68.0 68.9 68.6 67.0 65.35
BETA 15.15 13.55
20.4
18.9 14.3 16.55
18.75 19.75
GAMMA 11.3 11.25 10.7
13.1
16.75 14.85
14.25
14.9
BITUMENS
11.3
ULMINS
74.9
RESISTANT RESIDUES 13.8 14.0
..
76.1 *.
13:s 11.5 14.8
13.7
7317 77.2 78.1 78.6
0.7
0.6
0.1
i:ij
1:80 0.25 0.88
0:65 0.30
9.9
..
l2:5 11.3
7.1 7.7
YARIATION FROM MEAN OF ORIQINAL A N D RESAMPLE
Sunnyside 0.83 0.80 Thick Freeport 0.90 0.75 Pratt 0.15 1.28 Pittsburgh (Monongah) 0.73 0.45 AV. 0.65 0.82 a The value of 0.53 computed from 10 oxidation tests (a. 1 . ) is probably more significant than taken as the actual values of resistant residues.
0.03 1.30 0.95 0.32 0.65
the value of
0.55 0.80
0.35 on the
0.3P 3 oxidation tests of the table
ANALYTICAL EDITION
102
The figures for resistant residues, on the other hand, were puzzling at first, but it was learned later that Laboratory A had used a medium-porosity filtering disk for separating these residues from the potassium humate solution, while the authors had used a fine-porosity disk. The strength of oxidizing solution used for regenerating the ulmins was identical in the two laboratories. The conclusion was that a portion at least of the resistant residues must have passed through the filter in Laboratory A and been reported as ulmins. Such being the case, the variations from the mean of the values for resistant residues and ulmins are not significant, although the values for hydrocarbons and resins are comparable. The variations from the mean of the values obtained by Laboratory A and the U. S. Bureau of Mines for these constituents also are shown in this table. The average deviation of 0.4 computed from four samples is only slightly greater than the average obtained in the Bureau of Mines laboratory on duplicate samples. A comparison of four representatives coals from the Pittsburgh bed has proved interesting. Those studied were Ocean No. 2 from Allegheny County, Pa., Edenborn from Fayette County, Pa., Allison from Fayette County, Pa., and Monongah from Marion County, W. Va. The solvent extraction and rational analysis for these coals are summarized in Table IX.
Vol. 6, No. 2
10 11 4 13 2 3 16 8 19 14 1 20 18 17 12 9 16 7100E..
80 60 ~8
2i3
40 h
8& A6
w
-=
80 70
a 20
4 3
5312
!2g d&4 2s 0
420
400g 380 w 360 340 5 320 300 280 H 260
E E
44
TABLEIX. SOLVENT EXTRACTION AND RATIONAL ANALYSIS, PITTSBURGH BEDCOAL RESISTANT PLANT COAL ALPHA BETA GAMMA BITUMEINS ULMINS RBISIDUES 63.9 18.8 17.3 11.85 82.05 Ocean No. 2 6.10'3 62.2 26.6 14.3 76.9 Edenborn 11.3 8.80" 64.0 20.0 16.0 13.9 Allison 69.7 16.40" Monongah 68.0 17.8 14.2 14.8 78.1 7.104 Correapond to oxidationa with same oxidizing solution.
Here we observe notable similarities in the alpha, beta, and gamma of the Ocean and Allison. The bitumens are also fairly close together, but the resistant plant residues and ulmins are both significantly different. The total beta plus gamma is quite similar for three (the Ocean, Edenborn, and Allison), but it is low for the Monongah. The resistant residues, it is interesting to note, were all obtained by using the same strength and make-up of oxidizing solutions to regenerate the ulmins. COALCONSTITUENTS IN COAL CARBONIZATION It was attempted to correlate the data of Table I1 with as SIQNIFICANCE OF
many other properties of the coals, numerically expressible, as might conceivably bear a relationship. A comprehensive table was drawn up containing all values for the rational extraction and solvent analysis tests, and in addition, for fixed carbon, carbon-hydrogen ratio, volatile matter, cokehardness factor at 500" and 900" C. carbonizing temperature, initial contraction temperature, plastic range, gas yield at 500" C. carbonizing temperature, tar and light-oil yield, agglutinating index, swelling coefficient, 'coke stability (900" C., tumbler on 2.54 om.), and coke shatter (900" C. on 3.81 cm.). Columns were set up of ratios of solvent extraction and rational analysis data to every other listed property of the coal or its products of carbonization. This table proved a disappointment in that none of the ratios exhibited any degree of constancy through the series. Fifty-three curves were plotted in which the verticals from left to right represented the different coals in the ascending order of the beta, gamma, bitumens, or ulmins, other numerical values being plotted on the same verticals and the adjacent points connected by lines. These again were a disappointment from the standpoint of the lack of relationship that was so clearly evident in most cases. For the beta and
10 11 4 13 2 3 15 8 19 14 1 20 18 17 12 9 16 7
COAL NUMBER
FIGURE2. RELATION OF BITUMENS TO OTHER PROPERTIES OF COALAND COKE ulmins, no correlation at all could be deduced and for the bitumens and gamma, only a few curves seemed to bring out relationships. These are of the most general kind subject to interpretation and qualification. Exceptions to the rule are numerous. The first of these curves, Figure 1, shows the gamma plotted against the bitumens. As previous work had shown the gamma and bitumens to be on the same order of magnitude, the authors anticipated that the percentages of these two would closely parallel one another, the gamma possibly being slightly greater. That such is not the case is very evident from these curves, although the general direction of both is upward. Nevertheless the fluctuations are too numerous to warrant drawing conclusions. Portions of both the gamma and bitumens are undoubtedly identical, while certain other portions must be dissimilar, as it is possible to extract a benzene-extracted coal further with pyridine, and a pyridineextracted coal with benzene. This fact doubtless accounts for the fluctuations. Figure 2 shows a set of curves in which various values are plotted against the bitumens in the ascending order of bitumens. Some of these show no relationship at all but are included merely because they are functions of particular interest to the coal chemist. The general lack of relationship is evident from a casual glance a t the curves. Oxygen, carbon, volatile matter, tar and light oil, and swelling coefficient show no relationships at all to bitumens. Coke-hardness factor a t 900" C. has a
March 15, 1934
INDUSTRIAL AND ENGINEERING CHEMISTRY
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oxygen coals than are included here and has been able to generalize better for this reason. The carbon content rises slightly with the gamma, but the volatile matter tends to go down. Notable deviations in the case of the volatile matter are found for coals Nos. 4 and 11. No. 4 is a semi-bituminous coal and therefore low in volatile matter. No. 11 is also of fairly high rank (carbon, 87.4). Tar plus light oil rises fairly consistently with the gamma for low orders of the latter but as the gamma becomes fairly high there is a tendency toward deviation. Initial expansion and contraction temperature curves indicate no definite trends, but are included to show the contrast between them and similar curves for the bitumens, as the latter were fairly definitely correlatable with these functions. A mild relationship is indicated between the gamma and the coke shatter, 900' C. on 3.81 cm., the trend of the latter being slightly upward on the average. The coke stability, 900" C. on 2.54 cm., however, shows little if any relationship. CONCLUSION The conclusion to be drawn from this intensive study of the relationship between solvent extraction or rational analysis data with other properties of coal is that one may interpret little from a knowledge of the quantities present of extractable constituents, with respect to significant differences in the restricted range of coking coals. Such few relationships as have seemed to be apparent from the charts shown are slight indeed and leave considerable room for doubt. For example, it would be unwise to predict with assurance any aspect of the behavior of coal during the coking process or any property of the coke produced, from the results thus far obtained. LITERATURE CITED Kester, E. B., Selvig, W. A.,
(1) Fieldner, A. C., Davis, J. D.,
Reynolds, D. A., and Jung, F. W., Bur. Mines, Tech. Paper
COAL NUMBER
FIGURE3. RELATION OF GAMMA TO OTHER PROPERTIES OF COALAND COKE
.--
511 (1932). --, (2) IbG:, 543 (1932).
(3) Fieldner, A. C.,Davis, J. D., Thiessen, R., Kester, E. B., and Selvig, W. A.. Bur. Mines, Bull. 344 (1931). (4) Fieldnei, A. C., Davis, J. D., Thiessen, R., Kester, E. B., Selvig, W. A., Reynolds, D. A., Jung, F. W., and Sprunk, G. C., Ibid., Tech. Paper 519 (1932). (5) Ibid., 525 (1932). (6) Ibid., 524 (1932). (7) Ibid., 531 (1932). (8) Ibid., 542 (1932). (9) Ibid., 548 (1932). (10) Fischer, F., Broche, H., and Strauch, J., Brennstoff-Chem., 5, 299 (1924); 6, 33 (1925). (11) Francis, W., Colliery Guardian, 146,867,912 (1933). (12) Francis, W., and Wheeler, R. V., J . Chem. Soc., 1928, 2967-79; 1931.5 8 6 9 4 . (13) Jones,-D. T., and Wheeler, R. V., Ibid., 107, 1318-24 (1915); 109, 707-14 (1916). (14) Roberts, J . Fuel Econ., 8,507 (1933). (15) Shimmura, T., J. Fuel Soc. J a p a n , 11, 140-9 (1932). (16) . , Stones. M.. and Wheeler. R. V.. "The Constitution of Coal"' Dept. Sci. Ind. Research, p. 41 (1918).
rather persistent downward inclination with rising bitumens with but few exceptions. The initial expansion temperature curve is more satisfactory still from this standpoint, as it shows a fairly smooth decline with increase in bitumens. The initial contraction temperature likewise is downward, but the fluctuations are wide. Coke-stability factor (900" C.) shows a general tendency to decline with bitumen increase, though the descent is not a t all regular. Values for the coke-shatter test (900" C. on 3.81 cm.) on the other hand appear to descend almost to the midpoint and then to rise. Neither of these two curves will permit drawing definite conclusions. Figure 3 shows the curves for the same functions plotted against gamma values in the ascending order of gamma. Oxygen appears to fall slightly with increase in gamma. This property is in accord with the recent findings of Shimmura (15), who, however, has studied many more high-
RBCEIVBD September 26, 1933. Preeented before the Division of Gas and Fuel Chemistry at the 85th Meeting of the American Chemical Society, Washington, D. C., March 26 to 31, 1933. Published by permission of the Director, U. S. Bureau of Mines. (Not subject to copyright.)
INDUSTRIAL USESOF COLOR CHARTS.Extensive use of various forms of charts as standards for color in specification of commodities is revealed by Bureau of Standards Letter Circular 358. The U. S. Army uses rectangles of silk as color standards for textiles, and colored paper cards as standards for paint, in the urchase of these materials. Colored cards are used by the Eureau of Aeronautics as standards for finishing material for aircraft. As a part of standardization of their products effected in cooperation with the Bureau of Standards, the school furniture industry adopted stained blocks of wood for color standards,
and the sanitary ware industry adopted vitreous color standards. Extensive systems of color charts for general use have been published. The textile and allied industries have adopted "Standard and Seasonal Color Cards," in which silk is used for the standards. Despite the important part color plays in the paper industry, little efforthas been made t o standardize paper colors. It would seem that the use of standard color charts by the paper industry, rather than the present practice of matching samples submitted with orders, would lead t o economy and the better satisfaction of all concerned.
