化学链氧解耦燃煤发电系统过程模拟

Process simulation on chemical looping oxygen uncoupling coal-fired power generation system

当前煤的化学链燃烧中煤主要通过以下3步进行转化:煤的热解、煤焦的气化以及煤热解和气化产物与氧载体的反应。由于煤焦的气化反应速率较低,燃烧转化全过程受限于较慢速的煤焦气化过程,导致燃烧效率和CO_(2)捕集效率的下降。化学链氧解耦燃烧采用具有吸释氧能力的氧载体,煤焦可以与氧载体释放的气态氧直接反应而转化,避免较慢速的煤焦气化过程,显著提高燃料的转化速率。运用Aspen Plus软件构建了以CuO/Cu_(2)O为氧载体的600 MW化学链氧解耦燃煤发电系统。基于系统仿真结果,分别进行了能量、[火用]和[火用]成本分析。结果表明:化学链氧解耦燃煤发电系统的净热效率为37.66%;系统中内部[火用]损失最大的组件为燃烧反应器,占子系统总内部[火用]损失的44.23%。仅以发电量为产品时,化学链氧解耦燃煤发电系统的[火用]效率为36.27%;如果将高浓度CO_(2)也作为产品,系统的[火用]效率为40.47%;化学链氧解耦燃煤发电系统中单位[火用]成本最大的组件为第7台给水加热器,其次为第5个低压汽轮机、凝汽器、第1个高压汽轮机和空气预热器。

At present,the chemical looping combustion of coal comprises of the following three steps:coal pyrolysis,coal char gasification,and the reaction of coal pyrolysis and gasification products with oxygen carrier.The entire combustion conversion process is limited by the slower coal coke gasification process,which lead to a decrease in combustion efficiency and CO_(2)capture efficiency.Because of the oxygen carrier used in chemical looping oxygen uncoupling combustion with the ability to absorb and release oxygen,coal coke directly react with the gaseous oxygen released by the oxygen carrier,avoiding the slower coal coke gasification process and significantly improving the fuel conversion rate.This paper builds a 600 MW chemical linked oxygen decoupling coal-fired power generation system using CuO/Cu_(2)O as oxygen carrier using Aspen Plus software.Based on the simulation results of the system,energy,exergy,and exergy cost analyses were conducted separately.The results show that the net heat efficiency of the chemical looping oxygen uncoupling coal-fired power generation system is 37.66%;The component with the highest internal exergy loss in the system is the combustion reactor,which accounts for 44.23%of the total internal exergy loss in the subsystem.When only the power generation is used as a product,the efficiency of the chemical looping oxygen uncoupling coal-fired power generation system is 36.27%.If high concentration CO_(2)is also used as a product,the efficiency of the system is 40.47%.In the chemical looping oxygen uncoupling coal-fired power generation system,the component with the largest unit exergy cost is the seventh feedwater heater,followed by the fifth LP turbine,condenser,the first HP turbine and air preheater.