Optimization Of Oil Shale Comprehensive Utilization System Based On Gas Heat Carrier

Oil shale is a kind of sedimentary rock which is rich in organic matter.It can not only be used to produce shale oil by retorting,but also be used for power generation.There is a huge oil shale reserve in China,ranking the forefront of the world.With the increasingly severe energy shortage in recent years,especially in China,where oil is scarce,efficient use of oil shale resources makes sense for ensuring Chinese energy security.Based on the integrated theory of oil shale utilization,this paper partially optimizes Hua-dian oil shale comprehensive utilization system based on gas carrier technology.The small particles of oil shale which cannot be used for retorting and all the semi-coke are fed into the gasification furnace to produce syngas.The use of syngas can be divided into two ways.Firstly,the syngas can be directly sent to the gas-combined cycle power generation system.Besides,it can also enter Fischer-Tropsch synthesis system and then the remaining exhaust gas come into the combined cycle power generation system;accordingly,this paper constructs two kinds of comprehensive utilization system.In the new systems,the heat of heating carrier is mainly from two ways,namely,the heat recycled from the high temperature syngas and the exhaust gas of the gas turbine.Therefore,the inefficient semi-coke heating equipment and gas heating equipment in the original system can be removed.The small particles of the oil shale and semi-coke that cannot be used for retorting in gas carrier are made full use of by the oil shale comprehensive utilization system constructed in this paper,which greatly improves the total energy efficiency of the system,achieves the cascade utilization of energy,and reduces the emission of solid and gaseous waste.Two comprehensive utilization systems are simulated with Aspen plus.The logistics balance,energy balance and exergy balance of the system are calculated.Furthermore,the influence of the mixed gas of retorting-gasification and the mass fraction of oil shale for retorting on the energy efficiency and the product distribution in the newly constructed comprehensive utilization system is analyzed.The results show that the energy efficiency of the newly constructed oil shale retorting-gasification-power generation system and the retorting-gasification-FT synthesis-power generation system is 58.23% and 64.85% respectively,which is 1.17 times and 1.31 times of the original Hua-dian system.At the same time,the exergy efficiency of the two systems also reaches 60.18% and 66.1%.Further analysis suggests that an increase in the mass fraction of the mixed gas in the F-T process and the mass fraction of oil shale for retorting can both effectively improve the total energy efficiency of the system.In addition,the retorting-gasification-FT synthesis-power generation system has higher energy efficiency and liquid fuel yield compared with retorting-gasification-power generation system,but in terms of power generation,the former is much less than the latter.In industrial production,we can choose between the two systems or combine them reasonably by taking into account the economic efficiency or other factors.