I&EC REPORTS A N D C O M M E N T S Getting more oil from the shale
A basic study of ammonia decomposition Upgrading gasification processes with dolomites
OIL SHALE
YAKE UP HYDROGEN
RECYCLE HYDROGEN
sized by the state of the spent shale. After hydrotorting, the shale is easily reduced to a powder passing through a 200-mesh sieve, indicating that kerogen is the principal binder holding the shale together. Hydrogen requirements in the test apparatus were about 1600 SCF per ton of raw shale, obtained from the partial oxidation of 4 gal. of the most undesirable portion of product. Sufficient dry gas is produced in the hydrotorting step to supply fuel for the process with some left over for further processing. This reduces liquid yield of the plant to 100% of the Fisher assay. High efficiency of the process is due in part to the suppression of coking by the hydrogen, and in part to the reduced thermal energy needed for subsequent extraction. In addition, the products of the retort are hydrocarbons already mixed with hydrogen which can be immediately sent to a catalytic converter for further processing.
I 1 4 A 1000-2000 p.r.i.g.
SHALE BE0 400 Ibr.
ACCUMULATOR
/ / ,OIL
1000°F -
M E R
U
The recent increased expenditures for devising a better method of recovering shale oil have yielded some initial results indicating the possible trends in development. W. G. Schlinger and D. R. Jesse of Texaco reported to the ACS Division of Petroleum Chemistry at the New York Meeting on their work in hydrotorting of oil shale. I n nearly all the retort systems suggested thus far, heated air has been employed to burn off residual organic material after a major portion of the material (called kerogen) has been decomposed and removed by the hot gases. Though shales may contain between 25 and 50
gal. of oil per ton, the usual retorts leave the equivalent of about 12 gal. per ton in the spent shale. This residuum is potentially recoverable as liquid hydrocarbon under the right circumstances. I n the hydrotorting scheme, the entire oil content of the shale is stripped by using hot hydrogen at pressures up to 200 p.s.i.g. in the recycle system shown below. In this system less than 1% of the organic carbon remains unconverted to hydrocarbons. Comparative results with the conventional retort are shown in the table. The effectiveness of hydrogen as a retorting medium is further empha-
Air Retort
H-Retort
31.6-33.3
33.4
30
37.1.
90-95
111
Raw shale Fisher assay (gal./ton) Product yield (gal./ton) Product oil basis Fisher assay
(vol. yo,
ELEMENTARY REACTIONS LEADING TO DECOMPOSITION OF NH3 A study of the decomposition of ammonia by ionizing radiation with a wide-range radiolysis source has been conducted by Dr. C. E. Melton of the Oak Ridge National Laboratory. Ideally such a study involves a knowledge of the various ions, free radicals, excited states, and other transient species produced during irradiation, as well as the mechanism giving the reaction products. Much work has been carried out on the ammonia system, but the elementary reactions leading to final products have heretofore been obscure. (Continued on $age 74)
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B
aint Vehicle Demonstration Laborr'iry I
SREASA L q IAYICE
TRlS AMINOo-lOO
1
The wide-range radiolysis source consists of three units in series, each with a separate electron beam which can be independently controlled over a range of intensity and energy. The pressure in the source can be varied from 10-B to 10 torr. Reactions can be followed in time from about lo-" second after irradiation to the time for the formation of final stable products. Compartment three is a high sensitivity ion source which ionizes reaction products produced in a preceding compartment for mass identification by a sensitive mass spectrometer to which the apparatus is attached. Cross sections for ionization of both positive and negative ions by electrons are also measured in this compartment. Reactions which occur from approximately lo-" second to about 10- second after irradiation are studied in this compartment. Compartment two, the medium pressure compartment (lo-* - 1 torr), is used to measure rate constants for ion-molecule reactions, cross sections for the production of free radicals by electrons, and energy levels of excited states. In compartment two, reactions are studied which require times of the order of second to 1 second. Compartment one (pressure to 10 torr) is used for the initial radiation of the sample and to measure the threshold energy, the percentage of each component due to ion-molecule reactions, and G values (the number of molecules of product formed per 100 e.v. of energy absorbed). Irradiation of NHP with 100 e.v. electrons at a pressure of 1 torr produced 74.9% Ha, 24.9% Nz, and 0.2% NIH, as reaction products with G values of 8.8,2.9, and 0.03, respectively. Positive ion-molecule reactions produced 54% of the HI, 63% of the Nz, and 20yo of the NnH4. All the products appeared a t a threshold energy of approximately 4 e.v. corresponding to the energy necessary to
U
r - m e e d TA 011
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I N D U S T R I A L A N D E N G I N E E R I N G CHEMISTRY
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produce H - and NHt- from NHa by electron bombardment. The primary products of irradiation were 58.8% positive ions, 40.8% free radicals and neutral species, and 0.4% negative ions. The total cross sections observed were: posinegative ions, tive ions, 2 X lo-"; and free radicalq4.4 X 1.4 X 10-16 cm.a/molecule. In addition to the free radicals produced by dissociation of NHP, the secondary radicals NH,, NIHs NpH, and N2Ha were observed. Appearance potentials were measured and in some cases calculated (by an energy calibrated molecular orbital scheme) for the free radicals and the following values in e.v. were obtained: H (13.8); N (14.6); NH (12.8); NHI (11.7); NIHI (9.9); N& (7.6); NpHi (8.8); theoretical: NHI (10.5), NIHz (lO.l), and NpHs (7.8). The most abundant positive and negative ions observed a t 1 torr pressure were",+, 83%, and NHP; 51%. Careful analysis of the data collected shows the elementary reactions leading to the reaction products tobe:
-
+ "4 -.NE& + NH, + "* + H* N&* + NHa N a . + NH- + "4 N&N ~ ~ I - - N z H ,+ HZ+ "*f
"4
e
4
"I
4
e
I t is shown that "I, H, and NH.+ are the most important transient species in the reaction mechanism and that essentially all the primary ions formed react with NHs to produce NH4+and either H or NHI. The technique of using the widerange radiolysis source to study the elementary steps in a chemical reaction gives the researcher a new approach to reaction analysis. The equipment for these studies is within the scope of laboratories having a mass spectrometer.
DESULFURIZING WITH DOLOMITES The use of dolomite, in several of its possible forms, as a catalyst, promoter, adsorbent, and thermal controller in gasification applications dates back, at least, to the British Patent issued to duMotay and Marechal in 1867. Since that time gasification of solid and liquid fuels has undergone many refinements in which the roles of dolomite have undergone little change. I n particular, the use of dolomite to desulfurize has not been exploited, presumably for thermochemical and economic reasons. New evidence now indicates that dolomite may now add desulfurizing fuel gases to its other abilities. The ability of calcined dolomite, a naturally occurring mixed carbonate of calcium and magnesium, to desulfurize fluid fuels has long been known. Its use for this purpose, however, has been hampered by the lack of a system in which the dolomite may be recycled after the economical recovery of elemental sulfur. I t is the belief of A. M. Squires that such a system is now possible. In a paper read to the ACS Division of Fuel Chemistry at the recent ACS National Meeting in New York, Dr. Squires described several possible systems, all of them used in conjunction with an advanced power cycle. The benefits derived are principally economic, although there is the additional benefit of removing sulfurous compounds from atmospheric exhausts. The possible systems center about the cyclic nature of Reactions 1, 2, and 3 below. Reaction 1 can be used to generate a gas stream containing HZS in a concentration
exceeding that necessary to feed a Claus sulfur recovery system. The remaining solid product can then be calcined, according to Reaction 2, to produce a calcined dolomite containing CaO. The CaO is, in turn, used to remove H2S from a fluid fuel. Reaction 3 generates C a s by removing the H2S which is subsequently rejected in Reaction 1, and the cycle repeats itself. I n addition to desulfurizing the fuel, the calcined dolomite may be used to remove COz from a gas stream, to convert CO and steam to Hz, and to participate in the gasification of carbon by steam. As previously mentioned, the recovery of elemental sulfur, particularly from the Cas, has impeded the use of an integral sulfur recovery system. The cyclic scheme of Reactions 1 , 2 , and 3 may be augmented by the CO shift (Reaction 4), and the gasification of carbon (Reaction 5). Dr. Squires notes that Reaction 5 is the basis of the carbon dioxide acceptor process described at the Fuel Division’s symposium at the ACS National Meeting in 1964 by G. P. Curran, C. H. Rice, and E. Gorin of the Consolidation Coal Co. He believes that the acceptor process could be modified by incorporating Reaction 1 directly. The proposed desulfurization systems reject little heat at low temperatures. They have the further advantage of eliminating the cooling of great quantities of gas for low temperature sulfur removal, heretofore a bottleneck. To support his proposals, Dr. Squires cites new thermochemical data from bench
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(Continued on page 76)
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studies and reviews the critical areas of dolomite chemistry. Immediate response to the proposed systems could best be termed skeptically optimistic. The peculiarities of dolomite and its various forms make it chemically sensitive in the temperature ranges of interest in power plants. O n the other hand, the mechanical properties are quite adequate to permit the use of dolomites in fluidized beds, a key requirement in some of the proposed schemes. Even when allowance is made for Dr. Squires's obvious enthusiasm, the prospect for the use of dolomites as desulfurizing agents, in addition to their other abilities, is economically interesting. The added incentive of atmospheric pollution control might well spell the difference between a good idea and an interesting curiosity.
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INDUSTRIAL AND ENGINEERING
CHEMISTRY
If instrumenting process streams isn't enough, it appears that we may now have reached the doorway of instrumenting the chemist himself. Warner-Chilcott Laboratories, of Richmond, Calif., have introduced a machine that performs routine \vetchemical analyses up to 5 times faster than the chemist, and with a consistenc). of technique that ma)- make the chemist an also-ran. The machine holds 100 samples, and may be programmed to pipette samples, add diluents, add measured amounts of reagents, incubate samples, spectrophotometrically analyze, convert the analysis to digital form, and print out the analysis with a sample identification. The analysis may also be fed to a computer storage for reference. Although originally intended for clinical testing, the automatic s)-stem is applicable to any industry Xvhere routine wet-analyses are used. The system is particularly attractive for the anticipated antipollution program, since it may be operated without a trained chemist on hand.
