Some Effects of Pressure on Oil-Shale Retorting

A series of batch-type retorting experiments 930 degrees F were performed to investigate the effect of pressure and surrounding atmosphere on the retorting of oil shale. The experimental pressure ranged from atmospheric to 2,500 psig. pressure ranged from atmospheric to 2,500 psig. The sweeping gases used were N2, COe, H2O, NH3 and H2. We found that high pressure reduces the oil yield significantly and produces a larger volume of light hydrocarbon gases. The crude shale oil obtained at high pressure has higher aromaticity and a lower pour point than the low pressure material. The sulfur pour point than the low pressure material. The sulfur and nitrogen content in shale oil does not change significantly with increasing pressure. The effect of sweeping gas is usually small. In general, gases which decompose to yield H2 increase the oil yield at high pressure. At atmospheric pressure there is no effect. The high oil yield with H2, pressure there is no effect. The high oil yield with H2, more than 100 percent of the Fischer Assay, reported on "hydrotorting" experiments was not observed in this work. Introduction The in-situ retorting of oil shale has attracted much interest because it obviates the troublesome problem in surface retorting of mining, crushing and problem in surface retorting of mining, crushing and handling a large quantity of oil shale. The cost of these operations in the surface retorting process amounts to more than half the total production cost of shale oil. From an economic point of view, the recovery of shale oil by in-situ methods is highly desirable At present in--situ retorting is accomplished by combustion or hot gas injection, following conventional hydraulic fracturing. Explosive fracturing also has been studied. While these methods of fracturing are promising, there is still much uncertainty associated with them. On the other hand, even if an adequate mass permeability could be created, the high pressures encountered at depths of several thousand feet where oil shale commonly existwould certainly affect the thermal decomposition of oil shale. Thomas has experimentally simulated the effects of overburden pressure on the physical and mechanical properties of oil shale during underground retorting. Allred and Nielson studied the effect of pressure in reverse combustion on the yield and pressure in reverse combustion on the yield and quality of oil produced. These results are fragmentary and are applicable only to reverse combustion. Grant reported an oil yield of 35 to 40 percent of the Fischer Assay was obtained in a laboratory forward combustion experiment at 500 psig. We decided to investigate the effect of pressure on oil shale retorting because so little information was available on subjects. We sought to determine me effects of fluid pressure and surrounding atmosphere on the quantity and quality of products obtained from retorting oil slide. Results of a series of batch-type retorting experiments are reported. EXPERIMENTAL EQUIPMENT A schematic drawing of the retorting and product-collecting system is shown in Fig. 1. The pump product-collecting system is shown in Fig. 1. The pump delivers the sweeping gas at a constant rate to the retorting unit, which is maintained at the experimental pressure. The gas purged from the unit passes through pressure. The gas purged from the unit passes through a glass adapter to a centrifuge tube that is cooled by an ice-salt mixture. The gases are cooled further in the condenser that is kept at 32 degrees F and then sampled, measured through a wet-test meter, and vented. The retorting unit is an Autoclave single-ended reactor of 2–3/16-in. ID and 8–1/4-in. inside depth, rated 3,000 psi at 1000 degree F. SPEJ P. 287