Pyrolysis of Oil Shale

Sample preparation for the modified Fischer assay technique, a standard method to determine the Hquid yields from pyrolysis of oil shale, is necessary to achieve reproducible results. A 100-g sample of >230 fim (65 mesh) of oil shale is heated in a Fischer assay retort through a prescribed temperature range, eg, ca 25.5—500°C, for 50 min and then soaked for 20 min. The organic Hquid which is collected is the Fischer assay yield (7). The Fischer assay is not an absolute method, but a quaHtative assessment of the oil that may be produced from a given sample of oil shale (8). Retorting yields of greater than 100% of Fischer assay are possible. 

Other large-scale coal pyrolysis process developments were carried out by the Tosco Corp., with its TOSCO AT, process (36). Essentially a direct copy of Tosco s rotating kiln technology that was developed for pyrolysis of oil shale, this slow heating scheme achieved tar yields at maximum temperatures of 482—521°C that were essentially identical to those obtained by a Eischer assay. 

Particle coating Maleic anhydride synthesis Pyrolysis of oil shale Fluidized catalytic cracking... 

Retorting Pyrolysis of oil shale to produce oil in a vessel called a retort. 

Similarly to the study on coal, of significant importance was the evaluation of polycyclic aromatic compounds generated from the pyrolysis of oil shale. This type of study included the evaluation of PAH in shale pyrolysates, and also of sulfur containing polycyclic aromatic compounds, and nitrogen containing polycyclic aromatic compounds [41 aj. 

Saxby, J.D., and Stephenson, L.C., In situ pyrolysis of oil shale at Rundle (Australia) by igneous intrusion, to be published in "Organic thermogeochemistry" R. Ikan and and Z. Aizenshtat (eds.,) Springer-Verlag... 

This paper reports on the use of -H NMR thermal scanning for studying the pyrolysis of oil shales. 

Williams, P.T. Nazzal, J.M. Pyrolysis of oil shales influence of particle grain size on polycyclic aromatic compounds in the derived shale oils. J. Inst. Energy 1999, 72 (491), 48-55. 

The values of E and log A from the DSC experiments considerably exceed those from TGA. The DSC pyrolysis of oil shale Aleksinac has two endothermal peak maxima. Depending upon the heating rates (j8= 5, 10, 20 K/min) the first peak maxima appear at temperatures of 457 °C, 467 °C, and 477 °C, whereas the second peak maxima appears at 550 °C, 568 °C, and 583 °C. The kerogen concentrate srunple A-K behaves in a similar fashion, whereas the bitumen A-B-773 exhibits only one maximum at temperatures of 148 °C, 454 °G, and 469 C. 

The activation energy E and the frequency factor logA of the pyrolysis of oil shale Knjaievac (sample K) have high values which cannot be explained. The oil shale Estonia [sample E) has two distinct peaks in the DSC curves, below and above 500 °C (773 K). fter several hours of pyrolysis at 550 °C (823 K) or above, an additional weight loss Dccurs, indicating reactions of the mineral matrix of the oil shale. Therefore the activation... 

Fig. 4-116 Pattern of the Multistep Model for Pyrolysis of Oil Shale according to [4-49]...

These differences in pyrolysis behavior of the oil shales can be explained by structural differences in the corresponding kerogen types. The kerogens of oil shales Aleksinac, Estonia, and Korea are associated with type I, which is of predominantly paraffinic nature. Oil shale Knjazevac is associated with kerogen type HI, which is of predominantly aromatic nature. Thus the multi-step model appears to be suitable for simulating the pyrolysis of oil shales with kerogen type I, but cannot be properly adjusted for the other kerogen types. 

Modelling and simulation do not have to be limited to the pyrolysis of oil shales. Any pyrolysis process can be treated in similar manner, breaking it down into a series of consecutive and parallel reactions. The simulation will fit the real behavior so much the better, when as much information as possible is available on the original substances and intermediates. 

Arnold, Ch., Jr. Effects of Heating Rate on the Pyrolysis of Oil Shale, in L. F. Albright and B. L. Crynes (Ed.) Industrial and Laboratory Pyrolysis ACS Symposium Series No. 32, p. 492-503 American Chemical Society, Washington 1976. 

In the early work of Hubbard and Robinson, (l ) the pyrolysis of oil shale was treated as a first order reaction. Recently, Faucett, George and Carpenter (k) proposed a model based on a thermal decomposition system consisting of two first order reactions and three second order reactions which provide a better fit to the Hubbard and Robinson data. Our results tend to confirm the existence of higher order effects and are generally in accord with the model proposed by Eaucett, et. al. It is considered noteworthy that the highest reaction orders that we observed were associated with decomposition at the lower conversion levels where the activation energies were found to be low. 

Mechanism of Pyrolysis. Allred proposed the following mechanism for the pyrolysis of oil shale.(2)... 

Particle separation Vinyl acetate S5mthesis Nitrobenzene hydrogenation to aminobenzene Olefin pol5nneiization Pyrolysis of oil shale Silicon chloride to SiCljH Biomass pyrolysis... 

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