电站锅炉尾部烟气余热回收与梯级利用系统特性分析

燃煤电站锅炉实际运行排烟温度一般在130~150 ℃，进一步回收烟气余热有利于降低发电煤耗，减少污染物排放。针对电站锅炉尾部不同位置烟气参数不同的情况，设计了安装在空气预热器后及湿法脱硫装置后的两级热交换器余热回收系统，并结合330 MW燃煤电站锅炉，分析了不同负荷下，两级热交换器的换热量、冷凝水量、两侧介质静压差及发电标准煤耗降低值的变化情况，同时监测了二级热交换器前后烟气中固体颗粒物含量。结果表明：一级热交换器的换热量明显高于二级热交换器，烟气中水分主要在二级热交换器冷凝；标准煤耗降低值高达3.09 g/（kW·h）；同时烟气经过二级热交换器后固体颗粒物含量明显降低。为燃煤电站锅炉尾部烟气余热回收利用提供了参考。

System Characteristic Analysis of Waste Heat Recovery and Cascade Utilization of Tail Flue Gas of Power Boiler

The exhaust gas temperature of the power station boiler is generally 130~150 ℃. Further recovery of flue gas waste heat is beneficial for the reduction of coal consumption and pollutant emissions. Regarding the different flue gas parameters at various parts of the tail of the power station boiler, the waste heat recovery system is formulated with two-stage heat exchangers installed, i.e., one after the air preheater and the other after the wet desulfurization device. In consideration of the operation of the 330 MW coal-fired power station boiler, the effects of heat transfer, condensate and static pressure difference on both sides of the two-stage heat exchangers and the reduction of coal consumption for power generation were analyzed under different load conditions. Change of solid particulate matter in flue gas before and after heat exchanger was also monitored. The results show that the heat exchange capacity of the primary heat exchanger is significantly higher than that of the secondary heat exchanger, and the condensed water mainly occurs in the secondary heat exchanger. The standard coal consumption reduction value can reach up to 3.09 g/(kW·h). Besides, the content of solid particles in the flue gas after the heat exchanger is significantly reduced. This paper provides certain reference value for the waste heat recovery of flue gas from power station boilers.