燃煤电厂低低温烟气处理系统模拟优化

Simulation and optimization of MGGH system in coal-fired power plant

低低温烟气处理(MGGH)系统循环水进出口温度决定着换热器的平均对数温差,从而影响降温换热器和再热换热器的换热面积;同时,由于降温换热器和再热换热器因低温腐蚀的缘故所采用材质不同,使得2个换热器的单位造价存在较大差异,需要综合换热面积和材料成本对MGGH系统进行最优化。使用Aspen Plus软件构建MGGH系统并进行数值模拟,利用该软件的敏感性分析工具,设定某电厂降温换热器循环水进口温度和出口温度双变量,求解最优运行参数。优化后,原设计循环水出口温度由95℃变为105℃,所需循环水量由619.677 t/h变为437.428 t/h,降温换热器和再热换热器的设备总价降低了5.02%,总换热面积增加了1.55%。

MGGH system cycle water temperature at inlet and outlet determines the logarithm mean temperature difference of the heat exchangers,which affects the heat transfer area of cooling and reheat heat exchanger. At the same time,the materials of cooling heat exchanger and reheat heat exchanger are quite different because of the low temperature corrosion. The difference of materials makes the unit cost of these two heat exchangers varying widely. Therefore,the MGGH system was optimized by considering heat transfer area and material cost factor integrally. The MGGH system was built with the software Aspen plus and simulated numerically. Using the sensitivity analysis of the software,two variables which are the inlet and outlet temperature of cooling heat exchanger circulating water temperature in a power plant are set,to find out the optimal operating parameters. After optimization,the originally designed circulating temperature at outlet increases from 95 ℃ to 105 ℃,the required yield of circulating water drops from 619. 677 t/h to 437. 428 t/h,the total price of cooling heat exchanger and reheating equipment,reduced by 5. 02%,and the total heat transfer area is increased by 1. 55%.