Vacuum process for recovery of oil from oil shale

A unique oil shale retorting method which operates at low pressures (5 to 10 torr) was developed. Investigations were conducted on one to five gram samples in a laboratory bench-scale reactor to determine the optimum retorting parameters. To demonstrate the feasibility of the method on a larger scale, experiments were carried out on a prototype reactor capable of processing 22 kg of shale in five hours. Initial studies of Green River Formation shale showed that the optimum yields of oil and high heating value gases were obtained at a retorting temperature of 420/sup 0/C to 450/sup 0/C and a residence time of one hour. Five gram samples of six grades of shale, ranging from 12 to 68 gal/ton were processed, and oil yields of 80 to 90% of the Fischer assay were achieved. Eastern shales were also processed in the benchscale unit, and oil yields of up to 200% of the Fischer assay and a high heating value gas were obtained at a retorting temperature of 400/sup 0/C. Retorting eastern oil shale in 200 torr of helium or 200 torr to 650 torr of hydrogen yielded less oil than retorting at a pressure of 0.1 torr. Oil yields of 92more » to 97% of the Fischer assay were obtained from western shale in the prototype reactor at a temperature range of 340 to 375/sup 0/C and 110% at 425/sup 0/C. For an eastern shale, the oil yield was 114% of the Fischer assay. Western shale oils obtained from vacuum retorting are similar in composition and properties to shale oils obtained from other retorting methods. Eastern oils from vacuum retorting contain less nitrogen and have lower pour points than western shale oils, but have higher sulfur and aromatic contents. High Btu gases are obtained from the vacuum processing of both western and eastern shales. The gas from western shale contains more carbon dioxide while the gas from eastern shale contains more carbonyl sulfide and sulfur dioxide. 27 references, 34 figures.« less