Estimating Oil Yield of Oil Shale from Its Specific Gravity I. C. FROST A N D K. E. STANFIELD Petroleum and Oil-Shale Experiment Station, Bureau of Mines, Laramie, Wyo.
T H E specific gravity of oil shale may be used as a rapid and practical method of estimating the oil yields of shales from a given source. A study of 32 oil-shale samples of the Green River formation from the Bureau of Mines oil-shale mine (3)a t Rifle, Colo., showed that a relationship existed between the oil yields of these shales determined by the modified Fischer-assay method ( 4 ) and their specific gravities. This oil yield-specific gravity relationship provides a convenient means of estimating the oil yields of similar shales from the same source. A further examination of 38 other domestic and foreign oil shales indicated that similar but numerically different relationships may be used to estimate the oil yields of shales from other specific sources. The modified Fischer assay is the present accepted method of determining the oil yield of oil shale (4). By this method, the oil shale is retorted in a special cast-aluminum retort, and the oil yield is determined by condensing and measuring the volatilized oil. An assay requires approximately 2 hours for completion, whereas, by the proposed method, several specific gravities can be completed in 1 hour in a manner similar to that prescribed by the -4merican Society for Testing Materials for determining the true specific gravity of burned refractory materials (1). From these specific gravities, the oil yields are estimated from a graph of the oil yield-specific gravity relationship established from representative samples of the particular deposit. The estimated oil yields are not as reliable as values obtained directly by the assav of the samples. However, they are accurate enough for certain control purposes in mining and processing oil shale, for which rapid results are desired. This method of approximating the oil yield of oil shale is similar to that proposed by Engelhardt for estimating the organic cont m t of Estonian kukkersite (3). Engelhardt showed that the relationship between the specific volume (volume of 10.0 grams) of kukkersitc and its organic content was nearly linear and gave an equation whereby the organic content could be calculated from the specific volume. The oil yield-specific gravity rela tionship for the Green River shales investigated was not linear, primarily because of variations in the inorganic materials in the different grades of shale.
tered in that area. The modified Fischer oil yields of the samples ranged from 10.0 to 76.6 gallons of oil per ton of shale and their specific gravities a t 60 "/60 O F. ranged from 2.544 to 1.668. 80
\%
1 .E
2.0 2.2 SPECIFIC GRAVITY, 6O0/6OoF.
1.6
2.4
2.6
Figure 1. Relation of Specific Gravity to Fischer Oil Yield of Colorado Oil Shale
Figure 1 shows the curve obtained by plotting the oil yields of the samples against their specific gravities. From this curve, the oil yield of each sample was estimated. The estimated oil yields differed from the actual oil yields by an average of 1.2 gallons of oil per ton of shale. The maximum difference between the determined and estimated oil yields was 3.0 gallons of oil per ton or an average of 3.9%. The va1uc.s for thr individual samples are givm in Table I. Table I.
Sample
PROCEDURE
So.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17
-4pproximately a 10-gram sample of the dry shale crushed to pass an 8-mesh-per-inch sieve is weighed accurately into a 2bml. Hubbard-Carmick pycnometer. Kerosene of known specifit gravity, which has been topped to approximately 392" F. (200 C.), is added to cover the sample. The mixture is stirred with a glass rod, and the shale particles adhering to the glass rod are washed carefully into the pycnometer with a small portion of the kerosene. Air bubbles in the mixture are removed by suction (that obtained from a water aspirator is sufficient), after which the pycnometer is filled with kerosene and placed in a water bath maintained a t 60" * 0.1" F. Additional kerosene may be required after cooling for several minutes. When the pycnometer and contents have attained constant temperature (about 20 minutes), the stopper is inserted firmly, and the excess kerosene is removed with a dry cloth. The pycnometer is transferred to an ice bath to shrink the volume of kerosene in the pycnometer, then washed with a stream of acetone and dried. Finally, the pycnometer is weighed and the specific gravity of the oil shale is calculated. The oil yield of the shale is then approximated from the specific gravity by an oil yield-specific gravity curve (similar to that given in Figure 1for oil shales from the Bureau of Mines oilshale mine) established for the particular oil-shale deposit.
19 20 21 22 23 24 25 26 28 27 29 30 31 32
EXPERIMENTAL
Specific Gravity and Oil Yield of Oil Shale from Vicinity of Rifle, Colo. Specific Gravity,
Modified Fischer Oil Yield, Gal./Ton
Estimated Oil Yield, Gal./Ton
2.544 2.501 2.428 2.419 2.364 2.352 2.333 2.327 2.322 2,272 2,224 2.193 2.193 2.183 2.168 2,139 2.116 2.107 2.030 2.027 2.015 1.986 1,962 1.929 1,899 1.895 1.856 1.817 1.778 1.680 1.673 1.668
10.0 10.5 12.4 16.4 18.2 18.9 21.1 20.0 19.6 25.3 26.5 26.1 29.8 29.6 29.8 32.9 36.3 31.7 41.8 39.6 42.9 45.1 48.6 47.7 49.9 53.4 55.2 57.1 61.8 71.7 75.5 76.6
9.5 11.0 11.7 15.2 18.2 18.8 19.8 20.0 20.5 23.5 26.2 28., 28.7 29.5 30.5 32.5 34.0 34.7 40.5 40.7 41.5 43.7 45.7 48.7 51.2 51.5 55.0 58.7 62.7 72.5 73.2 74.0
60°/600
F.
Gal./Ton Differencea% 0.5 0.5 2.3 1.2 0.0 0.1 1.3 0.0 0.9 1.8 0.0 2.6 1.1 0.1 0.7 0.4 2.3 3.0 1.3 1.1 1.4 1.4 2.9 1.0 1.3 1.9 0.2 1.6 0.9 0.8 2.3 2.6 1.2 3.0
5.0 4.8 8.5 7.3
0.0
0.5 6.2 0.0 4.6 7.1 0.0 10.0 3.7 0.4 2.3 1.2 6.3 9.5 3.1 2.8 3.3 3.1 6.0 2.1 2.6 3.6 0.4 2.8 1.5 1.1 3.0 3.4 3.9 10.0
Average difference Maximum difference Difference between oil yield by modified Fischer-retort method and estimated from specific gravity of oil shale.
The 32 samples of oil shale from the Green River formation a t the Bureau of Mines oil-shale mine used in this study were chosen to represent the different grades of oil shale likely to be encoun-
a
49 1
492
ANALYTICAL CHEMISTRY
Table 11.
Sample No. 51 52 53 54 55 56 57 58 59 60
Specific Gravity of Foreign and Domestic Oil Shales Source South .Ifrica
Australia
61 62
Brazil
63 64 65 66 67 68 69 70 71 72 73
Manchuria
74 75 76 77 78 79
80
Indiana
Kansas Kentucky Nevada
81 82 83
Ohio
84 85 86 87 88
Tennessee Texas Wyoming
Modified Fischer Oil Yield, Gal./Ton 33.3 45.0 45.6 68.8 99.8 28.2 82.9 114.7 135.9 147.2 31.3 33.6 26.1 26.3 38.6 18.1 55.9 56.8 4.8 8.6 9.7 12.4 14.3 10.9 8.1 5.6 11.5 16.4 10.2 22.8 7.1 9.8 14.7 52.8 3.7 7.3 7.4 39.8
Specific Gravity
600/600‘ i. 1.645 1.599 1,627 1. 5 1R 1.376 2,072 1 ,633 1.301 1, 2 3 1 1,258
1 . Flfi? 2.01li 1 .YO3
1.Yl.i I , j3!1
1.687 1.570 1.533
2,536 2.183 2.216 2.148 2.212
2,133 2.207 2.387 2.232 2.114 2.356 2.072 2.490 2.382 2.222 1.520 2.359 2.332 2.354 1.969
Table 11 gives the oil yields and specific gravities of 38 oil s l ~ n l tfrom ~ s four foreign countrit,s and eight states other than Colo-
rado. These data show that the numerical value of the oil yieldspecific gravity relationship for the specified Colorado oil shales is not applicable to all oil shales; however, they indicate that similar relationships may be obtained for oil shales from other specific areas. Furthermore, this rapid method of estimating the oil yield of shale may be useful for routine control purposes where time and equipment will not allow the determination of oil yields by the modified Fischer assay. SUMMARY
The relationship betwren the oil yield by the modified Fischer :may and the specific gravity of certain Colorado oil shales provides a practical means of estimating the oil yields of other oil shales from the same area. The oil yields estimated from the specific gravities of samples from the Green River formation in the Bureau of Mines oil-shale mine, Rifle, Colo., differed from the actual oil yields of the shales by a maximum of 3.0 gallons of oil per ton and by an average of 1.2 gallons of oil per ton of shale. The numerical value of the oil yield-specific gravity relationship for these Colorado oil shales was not applicable to all oil shales. However, it indicated that similar relationships may be obtained for oil shales from other specific areas, and this method‘of estimating the oil yield of oil shale may be adapted to rapid routine testing of oil shales where time and equipment will not allow assays to be made by the more reliable modified Fischer-retort assay method. This report represents the results of work done under a cooperative agreement between the Bureau of Mines, United States Department of the Interior, and the University of Wyoming. LITERATURE CITED
(1) Am. SOC. Testing Materials, Standards, Part 11,pp. 323-4, Designation C 135-40, 1946. (2) Engelhardt, D. von, Brennstof-Chem., 13, 10 (1932). (3) Gardner, E. D., Bur. Mines, Rept. Invest. 4269 (4pril 1948). (4) Stanfield, K. E., and Frost, I. C.. Ibid., 3977 (October 1946) ; 4477 (June 1949).
RECEIVED April 12, 1949.
Acid-Bleached Fuchsin Solution as Analytical Reagent ALBERT STEIGMANS 21 Manison St., Stoneham, Mass. [LUTED solutions of basic fuchsin, which are decolorized with sulfuric acid and to which formaldehyde is added after bleaching, have been recommended as a quantitative reagent for sulfur dioxide and thiols. The reagent is much less sensitive for thiosulfate. Other substances than thiols interfere with the sulfur dioxide reaction. Their reactions are less sensitive and slower for comparable concentrations than those of the thiols, but they are also more difficult to mask. The masking of thiols or thiosulfate can be achieved with mercuric chloride or with the chlorides of platinum and palladium( 11). The mercury-precipitated thiols and thiosulfates must be removed by filtration or centrifugation before the sulfur dioxide test is carried out; otherwise the sulfur dioxide reagent will react with the precipitate. The mercuric thiosulfate precipitate is even more reactive than thiosulfate itself, whereak the platinum and palladium precipitates are not reactive or much less so. Grant ( 1 ) was the first to point out unknown substances which interfere with the sulfur dioxide reaction and which, unlike the thiols, cannot be removed by masking with mercuric chloride. He removed the mercuric thiol precipitates by centrifugation before adding the sulfur dioxide reagent, which can be kept for a long time by working with two stock solutions.
Stock Solution I is made from 228 ml. of water, 22 ml. of concentrated sulfuric acid, 4 ml. of basic fuchsin (3% alcoholic solution), or 8 ml. of fuchsin in the case of Grant’s quantitative rocedure. The solution is made up with water to 400 ml. a n f a g e d 3 days. The precipitate which forms is decanted or filtered off, or, better still, the fresh solution is shaken with 150ml. of carbon tetrachloride, when the colloidal precipitate goes into the interface. This purification procedure with the aid of a separation funnel is useful under all similar circumstances. Stock Solution I1 is made by adding 5 ml. of 40y0 formaldehyde, to water to make 100 ml. Reagent. Before use, 10 parts of I are mixed with 1 part of 11. A sensitive reagent for ascorbic acid is obtained by taking 6 parts of 11. Grant ( 1 ) makes the interesting statement that the blanks of the tissues which he tested for sulfur dioxide give a slightly positive color reaction, although “it seems unlikely that it represents any naturally occurring sulfur dioxide.” The author’s experiments with gelatin, for which he introduced the test, have also shoiin interference by gelatin, even in the case of Eastman electrodialyzed gelatin and other gelatins that contained no sulfur dioxide. The interfering gelatin reaction is, however, much less sensitive and much slower than the reaction with sulfur dioxide. It could be still further subdued and almost inhibited by plati-
