Combined fluidized bed retorting and circulating fluidized bed combustion system of oil shale: 2. Energy and economic analysis

Abstract

Retorting oil shale can produce shale oil, semicoke, water and fuel gases. Shale oil can be used as an important substitute oil supply, and semicoke and fuel gases may be burnt as fuels. An interesting issue is about how to utilize and distribute the heat from the combustion of semicoke and fuel gases, not only providing enough heat for retorting oil shale, but also producing more available energy products and less energy losses. Based on a combined system of oil shale FB (fluidized bed) retort and semicoke CFB (circulating fluidized bed) boiler, a comprehensive process flow was developed and an optimization calculation was conducted to achieve mass and energy balances of the whole system. Simulation indicated that, burning semicoke and fuel gases from retorting Huadian oil shale at the retorting temperature of 490 °C could not only provide enough energy required for the endothermic oil shale drying and retorting processes, but also supply extra energy for power generation or heat supply. The sensitivity of various operating parameters on the performance of the process was also discussed to optimize the comprehensive utilization system of oil shale. This work provided a reference for developing the new comprehensive utilization technology of oil shale.