燃煤机组空气预热器烟气旁路烟水复合余热利用系统节能分析

Energy-Saving Analysis of Air Preheater Flue Gas Bypass Gas-Water Compound System for Waste Heat Utilization in Coal-Fired Unit

针对采用锅炉空气预热器进口烟气旁路深度余热利用技术的烟水复合回热系统,以某660 MW超超临界燃煤机组空气预热器进口烟气旁路中布置中低温省煤器为例,采用热平衡方法进行了投中低温省煤器与不投中低温省煤器2种工况对锅炉热效率及汽机热耗影响的试验研究。研究结果表明:投运空气预热器进口烟气旁路系统虽然造成锅炉排烟热损失增大,锅炉热效率降低约0.42%;但利用高品位烟气余热在空气预热器进口烟气旁路系统中加热高压凝结水排挤最后一级高压抽汽,汽轮机热耗降低,机组循环效率提升。工程应用表明,采用空气预热器烟气旁路烟水复合余热利用系统能使机组整体煤耗降低约1.98 g/(kW·h)。

For a flue gas compound regenerative system adopting an air preheater flue gas bypass waste heat in depth utilization technology,with a 660 MW supercritical coal fired power plant serving a medium temperature economizer in the flue gas bypass of the air preheater as an example,the method of the heat quantity balance has been employed to conduct an energy saving analysis on two conditions,with or without the operation of the medium temperature economizer.The research results show that the operation of the air preheater flue gas bypass system increases the loss of flue gas,and the boiler thermal efficiency is reduced about 0.42%;but the high-grade flue gas waste heat which has been used to heat the high-pressure condensation water in the air preheater flue gas bypass system could squeeze the last stage of high-pressure extraction steam so that the heat rate of the steam turbine could be reduced,and the cycle efficiency of the unit was improved.Engineering application has shown that the overall coal consumption of the unit could be reduced by about 1.98 g/(kW·h).