锅炉空气预热器并联旁路烟道最佳容量选择

Optimal capacity selection of parallel bypass flue for boiler air preheaters

锅炉空气预热器(空预器)并联旁路烟道系统是锅炉尾部烟气热量深度利用的重要方式,机组要获得最优的热效率需选择最佳的旁路烟道容量。本文通过热量守恒法对锅炉空预器并联旁路烟道容量及热负荷公式进行推导,并结合某超超临界1 000 MW等级燃煤机组对旁路烟道容量及热负荷进行计算,从而确定了旁路烟道最佳容量。结果表明:旁路烟道最佳容量选择与旁路烟道出口烟温、空预器冷端烟气与冷风平均温差和暖风器出口平均风温密切相关;机组在同等条件下,对比空预器冷端平均温差分别为40℃和50℃的计算结果得到,暖风器出口平均风温为50℃时,旁路烟道热负荷均为最大值,分别为51.601、43.261 MW,此时旁路烟道最佳容量分别为0.174、0.145。此结论可为火电厂锅炉空预器并联旁路烟道系统设计提供指导。

The parallel bypass flue system for boiler air preheater is an important method for advanced utilization of boiler tail flue gas heat.The optimal capacity of parallel bypass flue is selected for optimal thermal efficiency of units.The formula of capacity and heat load of parallel bypass flue for boiler air preheater is derived based on the law of heat conservation.Combined with an ultra-supercritical 1 000 MW coal-fired unit,the capacity and heat load of bypass flue are calculated so as to select the optimal capacity of bypass flue.The results show that,the optimal capacity selection of bypass flue is closely related to the flue gas temperature at the outlet of the bypass flue,the average temperature difference between the flue gas and the cold air at the cold end of the air preheater,and the average air temperature at the outlet of the air heater.Under the same conditions,according to the calculation results of the average temperature difference at the cold end of the air preheater(40℃and 50℃),when the average air temperature at the outlet of the air heater is 50℃,the maximum heat load of the bypass flue is obtained,which is 51.601 MW and 43.261 MW,respectively.At this time,the optimal capacity of the bypass flue is 0.174 and 0.145,respectively.It can provide guidance for the design of parallel bypass flue system for boiler air preheater in thermal power plants.