生物质热电厂化学吸收碳捕集控制策略改进

Improvement of control strategy of CO_(2) capture frombiomass CHP plant by chemical absorption

从生物质热电厂捕集CO_(2)时,生物质原料和电厂热电需求变化会影响化学吸收碳捕集系统性能。为应对这种影响,基于对传统反馈控制策略(控制策略A)的控制性能评估,提出了再沸器负荷控制的改进策略(控制策略B)以实现捕集率恒定。控制策略B以控制策略A为基础,引入了基于富液流量的前馈补偿,组成前馈+反馈的控制策略。通过对比2种控制策略的控制性能、灵活操作性能和捕集系统性能,寻求适合生物质热电厂化学吸收碳捕集的控制策略。基于实际生物质热电厂化学吸收碳捕集系统的动态仿真,得出以下结论:相对于控制策略A,控制策略B的前馈补偿缩短了再沸器负荷对外界扰动的响应时间,提高了对再沸器负荷调节的及时性和准确性,将捕集率调节时间缩短了54 min;面对捕集率设定值的灵活改变,控制策略B将稳定捕集率所需时间缩短了57.9%;在外界持续干扰下,控制策略B将捕集率维持在设定值±3%的同时,捕集单位质量CO_(2)能耗降低了0.14%,CO_(2)捕集总量提升了0.35%。同时,动态仿真与传统稳态模拟结果表明,动态仿真能更准确体现外界扰动对捕集系统的影响,为有关流程的集成和优化提供参考。

When capturing CO_(2) from biomass fired combined heat and power(CHP)plants,the changes in the feedstock and the heat and electricity demands affect the performance of chemical absorption CO_(2) capture system.To handle such impact,this paper proposed an improved reboiler duty control strategy(control strategy B)based on the evaluation of the control performance of the traditional feedback control strategy(control strategy A)to achieve a constant capture rate.Control strategy B is based on control strategy A,and introduces feedforward compensation based on rich solution flow rate to form a feedforward plus feedback control strategy.This work aimed to find a control strategy suitable for chemical absorption CO_(2)capture from biomass CHP,by comparing the control performance,capture system performance and flexible operation performance of both control strategies.Based on the dynamic simulations of CO_(2)capture from actual biomass fired CHP plant,it is found that compared with the control strategy A,the feedforward compensation of the control strategy B can reduce the response time of the reboiler duty to external disturbances,and improve the timeliness and accuracy of the regulation of reboiler duty.The settling time of capture rate is reduced by 54 mins with the control strategy B.Facing the flexible change of capture rate setpoint,the time required for the stabilization of capture rate is reduced by 57.9%with control strategy B.Under the continuous external disturbance,the capture rate is maintained at±3%of the setpoint with control strategy B.At the same time,the energy penalty is reduced by 0.14%,and the total captured CO_(2)is increased by 0.35%.In addition,the results of dynamic simulation and traditional steady-state simulation show that the dynamic simulation can reflect the impact of external disturbances on the capture system more accurately,and provide a reference for the integration and optimization of related processes.