THE JOURNAL OF I N D U S T R I A L A N D ENGINEERTNG CHEMISTRY
Aug., 1921 -HEAVY Control A1
1 302
io6
B
2D
C
292 444 ,157 225 208
2 288
id4
305 442 160 264 220
FABRIC3 286
Av.
184 324 468 164 225 200
193 307 451 156 241 209
...
292
...
--LIGHT 1 212
2 188
170 138 190 144 210
182 124 188 148 198 I55
...
...
FABRI3 Av. 180 193
...
185 160 204 154 188 158
...
179 141 194 149 199 164
G 178 * No breaking tests could be obtained on t h e fabric treated with Solution A, inasmuch as the fabric had been so seriously affected by the alum as to be easily torn apart in the fingers.
Results with Tests C and D are contradictory in indicating a greater tensile strength in the case of the treated heavy fabric than the control possessed, while the effect on the treated light fabric was a weakening action with the first material and no perceptible effect with the sodium tungstate. This was probably due either to some error in obtaining the breaking strengths of the samples or to some unknown and unavoidable difference (e. g., air currents) in the drying of the test pieces. A second series of tests was carried out (in comparison with a new control) under the same conditions as the first tests but on a different day and consequently
677
with different humidity conditions. The results, which are more in accord with the first series obtained, are as follows. -HEAVY Control
c1 ,
Di
1 316 209 250
2 333 200 238
FABRIC-3 Av. 304 318 200 203 292 2GO
-LIGHT
1 229 188 230
2 212 215 216
FABRIC--3 Av. 228 223 184 195 200 215
CONCLUSIOXS 1-Of the three types of fireproofing agents tested, sodium tungstate is shown to have the least effect on the breaking strength of the fabric and therefore the least weakening action. 2-Furthermore, a test of the fireproofing qualities of the solutions showed the 3 . 5 per cent solution of sodium tungstate to be practically as efficient as the stronger solution. This, then, is recommended as an excellent fireproofing agent for the impregnation of cotton fabric whose breaking strength and wearing qualities must not be materially weakened by the process employed.
The Use of Nitroglycerin Spent Acid as Charging Acid for Nitric Acid Stills' By S. G . Norton HERCULES POWDER Co., WILMINGTON, DBLAWARG
The method of disposing of spent acid described in this paper has been known and used in America for several years. The spent acid, as received from the nitroglycerin plant, containing approximately 75 per cent H 2 S 0 4 and 7.5 per cent HNOJ, was treated essentially as follows: After standing in open tanks for 24 hrs. the spent acid was examined for free nitroglycerin. Any traces of the latter having been carefully skimmed off, the acid was drawn down into a mixing tank. Sufficient fuming sulfuric acid of approximately 108 per cent strength was added to bring the sulfuric content up to the desired percentage, a thorough air agitation being maintained during the addition and for some time thereafter. The resulting mixture, which was used to replace the usual 66" BO. sulfuric acid for charging the stills, Contained about 4.00 per cent of "0,. After using the charging mixture containing spent acid for several months, it was noted that a consistently lower yield was obtained from the nitric acid plant than had been obtained previously. The nitrosyl content of the mixed acid made at the plant increased. Poor separations were obtained in the nitroglycerin operations. These difficulties increased cumulatively with each round of the acid through the system.
SMALL SCALESTUDY OF PROCESS Since it appeared that the use of charging acid made from spents was of questionable advantage, a careful series of distillations was made on a laboratory scale to determine, so far a s possible, what was taking place in the nitric stills where the spent acid charging mixture was used. The apparatus used for the distillations consisted of a glass retort of about one-liter capacity, a condenser, and a receiver, all having ground connections. From the receiver the gases were drawn, under slight vacuum, through an absorption system consisting of three gas-washing bottles. The first two OS these contained water, and the third a 5 per cent solution of sodium hydroxide. All materials used were carefully analyzed. The acid and the v8.i-ious wash waters resulting from each distillation were also analyzed, tests being made for various substances which 1
Received February 9, 1921.
might affect the yield figure. The nitrate of soda used was uniform throughout the entire investigation, a large sample having been obtained and carefully blended a t the beginning of the work. The acids used were also obtained in large enough quantity so that the same sample could be used throughout a series. Three sets of distillations were made. The results of these distillations will be found in the table. The first set, in which straight 66' BO. sulfuric charging acid and nitrate of soda were used in a ratio of 1:1by weight, was carried out to determine what yield might be expected from the nitrate of soda under the conditions of the experiment. The average yield obtained was 99.13 per cent, calculated as total "03. For the second series, a charging acid was prepared from a sample of spent acid as received from the nitroglycerin operation, by mixing it with 108 per cent fuming sulfuric acid in the usual manner. The charging acid thus prepared showed the following analysis: Per cent HzSO4 HNOa
88.50 4 31
I n charging the retort an additional weight of this charging acid was used, so as to have the ratio of sulfuric acid to soda the same as in the preceding series. It will be noted from the accompanying table that, while an average of 75.762 g. of "0, was obtained, if we assume the same yield from the soda as the first series gave, i. e.. 99.13 per cent, 71.594 g. of the "0, are accounted for. This leaves only 4.168 g. of HN03 obtained from the charging acid. Since 4.741 g. of " 0 3 were introduced in the charging acid, we have a yield on the latter of only 87.91 per cent. A third series of distillations was made, in which charging acid prepared from a different sample of nitroglycerin spent was used. The analysis of this charging acid was: H&OI HNOa
Per cent 88 08
4 68
While a n average of 5.212 g. of "03 was introduced in the charging acid in this series, only 4.281 g. were recovered.
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T H E JOURNAL OF INDUXTRIAL A N D ENGINEERING CHEMISTRY
a yield of 82.16 per cent. These yields are very much lower than would have been obtained if the spent acid had been denitrated in the usual manner. The distillations made with spent acid charging mixture required a longer time for completion than did those made with straight charging acid. They were also distinguished by a copious and nearly continuous evolution of NO,. .An average of 2.75 per cent of the total yield was obtained as N02, as against 0.40 per cent where straight charging acid was used. The yield not accounted for in the distillations made with
Vol. 13, No. EG
spent charging acid was obtained in the form of NO, N,O,, and free nitrogen. Since these gases are not recoverable in! practice, they constitute a serious loss when formed in large quantities.
CONCLUSION As a result of the foregoing investigation, the use of spent acid for charging nitric stills has been abandoned a t this plant. The usual recovery operation was resumed, and after the. spent acid had been eliminated from the system the former satisfactory yields were obtained from the nitric acid plant.
Theoretically from Soda TheoreticalTotal Yield Yield Possible from with 99.13 l y Possible "0% Soda Used Per cent from as "03' KIND O F ACID Grams Grams Yield Soent Straight Charging (&Sod, 92.44 per cent) 71.641 0.346 72.220 71.577 0.360 72.220 71.554 0.410 72.220 AVERAGE 71.591 0.372 72.220 Sample 1, Spent Charging (HzSOd, 55.50 per 75.758 1.498 72,220 71.594 4.741 cent, "01.4.31 per cent) 75.770 1.517 72.220 71.694 4.741 75.758 1.314 72.220 71.594 4.741 AVERAGE.. , 75.762 1.443 72.220 71.594 4.741 Sample 2, Spent Charging (HnSOa, 5 5 . 0 4 per 75.900 1.623 72.220 71.594 5.245 cent. " 0 3 , 4 . 6 3 per cent) 75.869 1.706 72.220 71.594 5.195 75.856 1.878 72.220 71.594 5.195 AVERAGE.. , 75.575 1.736 72.220 71.594 5.212 I Total acidity calculated as " 0 3 minus nitric values for HCI and HzSO4. 2 This figure represents total yield as " 0 3 (Column 2) minus the average actual yield from the soda 99.13 per cent of that theoretically possible.
.............. . . . .. . . . . . .
. . .. . . . . . . . .
--PER CENT YIELDS--. Grams HNOB Actual "08 Total Actual Yield Total N o t Includ- HNOa from from Soent* " 0 3 ine NOa SDent 99.20 98.7599.11 95.44 99.08 98 .32 .~ 99.13 95.53 4.164 98.44 95.83 87.83 4.176 95.45 95.51 58.08 4.164 98.44 99.15 67.83 4.168 95.44 95.93 87.91 4.306 97.95 95.18 52.15 4.275 98.00 95.05 82.30 4.262 97.99 94.73 6.~ 2.04 4.251 97.99 94.99 52.16
used (Column 5 ) . The latter is calculated as
The Thermal Decomposition of Oil Shales. 11-Determination o f the Heat of Reaction Involved in Their Thermal Decomposition''z By Ralph H. McKee and E. E. Lyder . DEPARTMENT os CHEMICAL ENGINEERING, COWJMBIA UNIVERSITY, NEWYORK,N. Y .
.
The solution of the problem of the recovery of petroleum oils and other products from the so-called oil shales of this country must be based on exact information, such as the values of all the physical constants involved, a knowledge of the manner in which the oil-forming material decomposes, and information as to the character of the product obtained under varying conditions. Also, since it is apparently established that the only way to recover petroleum oils from shales is by thermal d e c o m p ~ s i t i o n , ~a ~study ~ ~ ~ of * the heats involved and the primary effect of heat on the shale is evidently most essential to the intelligent development of the industry. It has been the object of this research to study these hitherto little known factors in relation to their bearing on commercial retorting. A method has been devised for the determination of the amount of heat involved in the conversion to oil of the organic material in the shale, and the value has been determined on three quite different types of shale. It was found that these values for the three shales used ranged from 421 to 484 cal. per g. of oil and gas produced. The heat conductivity of the shale has been determined for this work, and the coefficient of thermal conductivity has been found to be 0.00086, expressed in e. g. s. units. The specific heat has been determined and found to be around 0.265 for most shales. Part I of this papert has shown that certain fundamental conceptions as to the manner in which the organic material decomposes are different from those ordinarily accepted. The hitherto generally accepted explanation of the manner in which these shales decompose is that, under the influence 1 Presented in part (together with Part I) before the New York Section of the American Chemical Society, New York, N . Y , January 7, 1921 a A dissertation presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in the Faculty of Pure Science, Columbia University, New York, N Y. * Numbers refer to bibliography at the end of the paper. t THISJ O U R N A18 L S (19211, 613.
of heat, the organic material breaks down from a highmolecular-weight, insoluble substance to form petroleumlike hydrocarbons. These hydrocarbons increase in density and boiling point as the temperature rises, that is to say, the first product of destructive distillation oE shale is the light hydrocarbon oil correspondbing to gasoline in physical properties. The next is a somewhat heavier product like that found in the kerosene fractions, and the next still heavier, and so on until, finally, heavy residuents, such as fuel oil and paraffin, are produced. Part I has also shown that the organic material does not decompose as above outlined, but that its first product of decomposition is a heavy solid or semi-solid bitumen soluble in carbon bisulfide, whereas the original material was but very slightly soluble. The production of petroleum-like oils is, then, the result of the decomposition of these heavy bitumens by cracking. The importance of this idea is that it places th"e production of oil, especially gasoline, from shales in the same category as the production of gasoline from the cracking of other oils. It should, therefore, promote the design of a shale retort along this line. At the beginning of this work little or nothing was known as to the amount of heat required to convert to hydrocarbons the pyrobitumen of the shale. It was not even known whether the reaction was endothermic or exothermic, and, as this could easily be a factor of prime importance in the design of a retort, it was decided to determine it experimentally. The design of the apparatus and the method of determining this constant are described in this paper. Also, there have been, included data on other heat factors, such as specific heat and heat of vaporization. Additional information can be obtained on these and other constants by consulting t h e original articles referred to.
HEATFACTORS 0 In the design of a retort it is desirable to know the quantity
