Oil shale pyrolysis

Numerous kinetic mechanisms have been proposed for oil shale pyrolysis reactions (11—14). It has been generally accepted that the kinetics of the oil shale pyrolysis could be represented by a simple first-order reaction (kerogen — bitumen — oil), or... 

Oil Shale Pyrolysis-Gas Chromatography. Another important aspect of gas chromatography as applied to oil shale characterization is the ability to carry out separations directly on volatiles evolved as samples are heated under controlled conditions. The method for heating small samples of oil shale in the laboratory clearly diflFers considerably from actual larger scale retorting procedures. In the latter case, secondary reactions of organic pyrolysis product certainly occur and they are subject to contact with water and air prior to work-up and analysis. However, a... 

Molecular Mechanism of Oil Shale Pyrolysis in Nitrogen and Hydrogen Atmospheres... 

Increased knowledge of the molecular transformations which occur during oil shale pyrolysis (retorting) is essential for maximizing the yield and quality of products from this vast source of hydrocarbons. Compared to other sources such as petroleum and coal, there is little known about the molecular structure of the insoluble organic material (kerogen) in oil shale. There is... 

Figure 1. A proposed reaction model for oil shale pyrolysis. (Reproduced with permission from Ref 4. Copyright 1981, Colorado School of Mines.)...

BURNHAM AND SINGLETON Green River Oil Shale Pyrolysis... 

The results presented are not part of a systematic study of oil shale pyrolysis but rather those of various experiments selected to demonstrate the utility and potential of the method. 

Finally, the fact that these organoarsonic acids are released upon oil shale pyrolysis has important implications in the various synthetic fuel processes, where the role of organometallic compounds in poisoning process catalysts and contributing to environmental problems, is paramount. (32,33)... 

Ground rules on temperature and pressure are set by typical retort conditions. For pressure, this is 1 atmosphere for temperature, this is 500-800°C (7). The composition of the gas is more difficult to establish, but for this study, it is assumed that most of the hydrocarbons have been pyrolyzed from the system and that reactions with the carbon char are taking place. This establishes the primary volatiles as CO, CO2, H20,and H2in roughly equimolar amounts. This assumption is based on typical retort gas analyses (16) and on laboratory studies of oil shale pyrolysis (5, 17), Establishing a more limited range on the temperature is dictated by that temperature at which decarbonation is definitely complete. This will be discussed later in the paper. For now, it s assumed that decarbonation is complete and that the temperature needed for this is at least 600°C. 

The decomposition of pure phase carbonate minerals has been extensively studied and reviewed (17). The influence of these minerals on oil shale pyrolysis kinetics has not been extensively studied, but the studies of Jukkola et al. (18) and Campbell (15) are notable. The results of both these studies indicate that the major calcite decomposition step is through reaction with silicate minerals in shale to produce Ca- and Ca-, Mg-silicates. The observed enhancement in pyrolysis yield after carbonate removal may be indicative of the catalytic role of silicate minerals in paraffinic and aromatic compound decompositions. In effect, an apparent preference for calcite-silicate interactions in raw shale limits silicate-catalyzed organic reactions which would presumably result in enhanced oil yields. It should be noted, however, that the silicate/carbonate ratio is increasing with net pyrolysis yield for the raw shales, Table I. This may reflect excess silicates becoming free to catalyze organic decomposition. 

The preceding observations suggest that indigenous silicate minerals contribute actively to oil shale pyrolysis. The silicates appear to react preferentially with carbonate minerals. Excess silicates, beyond the required amount for carbonate interactions, appear to catalyze the organic decomposition and organic-pyrite interaction. Indeed, the organic-pyrite interaction is not observed in the absence of sufficient silicates. These results are qualitative indications of trends which should be assessed in a more thorough and quantitative fashion. 

Chemical conversion of vegetable oils to general purpose liquid fuels ( biofuels, and biodiesel ) has also been successfully explored [34, 35]. However, the small size of this resource makes it unlikely that this could do more than supplement petroleum-based sources. Probably the more significant developments to extend petroleum-based liquid fuels lie in the recovery of oil from the tar sands, and the pilot plant projects involving oil shale pyrolysis experiments to liquid fuels. 

Sulfur gas containment from either oil shale pyrolysis or oil upgrading can be accomplished using the largely existing technology already outlined for tar sands processing. Environmental aspects of oil shale processing have been reviewed [54]. 

Gas Evolution During Oil Shale Pyrolysis I. Non-Isothermal Rate Measurements," Fuel 1980, 718. 

Most of the sulfur in oil shale occurs in pyrite and a smaller amount is contained in the kerogen. The major source of H2S during oil shale pyrolysis appears to be the reaction of pyrite with organic matter. In an autogenous atmosphere, most of the H2S evolves between 400 and 500°C. Addition of finely ground pyrite increases the amount of H2S evolved but does not change the evolution profile. In an argon atmosphere, however, added pyrite causes a substantial increase in H2S evolution... 

Campbell, J. H. Koskinas, G. J. Gallegos, G. Gregg, M. "Gas Evolution During Oil Shale Pyrolysis Part 1. Nonisothermal Rate Measurements," Fuel 1980, 59, 718. 

Jacobson, I. A., Jr. Decora, A. W. Cook G. L. "Retorting Indexes for Oil Shale Pyrolysis from Ethene/Ethane Ratios of Product Gases," in Science and Technology of Oil Shale, T. F. Yen, Ed. Ann Arbor Sciences Publishers Ann Arbor, MI, 1976 p. 103. 

Robillard, M. V. Siggia, S. Uden, P. C. "Effect of Oxygen on Composition of Light Hydrocarbons Evolved in Oil Shale Pyrolysis," Anal. Chem. 1979, 5 1, 435. 

Fausett, D. W. George, J. H. Carpenter, H. C. "Second-Order Effects in the Kinetics of Oil Shale Pyrolysis, Report of Investigation 7889, Bureau of Mines, Washington, D.C., 1974. 

Figure 4. Raining ball oil shale pyrolysis scheme...

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