PROCESS AND APPARATUS FOR MAXIMIZING OIL YIELD IN THE RETORTING OF OIL SHALE

摘要

An improved apparatus and method for the operation thereof for retorting oil shale with heat-carrying bodies wherein oil recovery is maximized. After retorting, the spent oil shale and heat-carrying bodies are steam stripped within the retorting vessel to maximize the amount -of oil-containing vapors delivered to the recovery apparatus. The stripped heat-carrying bodies and spent shale are then returned to a reheating vessel'. The reheating vessel contains a dense phase fluidized bed wherein the fixed carbon contained -in the stripped spent shale is combusted to reheat the heat-carrying bodies, the hot flue gases simultaneously elutriating fines contained within the mixture. The reheated heat-carrying particles and spent shale particles are steam stripped within the ccmbustion vessel to remove trapped flue gases before being returned to the retort vessel whereby contamination thereof is prevented. heat from flue gases, excess spent shale particles, and removed shale ash and fines is used to generate the steam employed in the stripping operations to maximize energy utilization. The invention is based on the finding that the decomposition of kerogen, which is present as a binder in raw oil shale, leaves pores within kerogen-rich shale which results in relatively large surface areas. Attrition o' the kerogen-rich shale in a fluidized bed operation at a superficial gas velocity of 7-14 ft/sec reduces the size of this porous, friable material and allows it to be removed in the exit gas stream. The larger particles remaining oriqinated as kerogen-lean shale and thus lack the surface area and resulting sorption capacity to adversely effect retorting. The recycled particles thus become effective heat-carryinq bodies. Recovery of sensible heat from the spent shale particles is accomplished in two fluidized bed coolers to maximize heat transfer and energy utilization.