基于工业供汽的给水泵背压式汽轮机驱动方案热经济性分析

Thermal economy research on back pressure turbine-driven scheme for feed water pumps based on industrial steam supply

配备电动给水泵组的燃煤机组普遍存在生产厂用电率偏高的问题,结合工业供汽实施汽动改造是解决该问题的有效手段之一。以国产某330 MW直接空冷机组为例,综合考虑低负荷预期和供汽量现状,确定了增设1台50%容量给水泵背压式汽轮机(背压机)的方案,定量计算了原压力匹配器与三段抽汽联合供汽方案、给水泵背压机汽源取自再热冷段-排汽供汽方案和给水泵背压机汽源取自再热热段-排汽供汽方案的经济性。结果表明:背压机汽源取自再热热段方案较原供汽方案可节约供电煤耗约1.6 g/(k W·h),而背压机汽源取自再热冷段方案较原方案可节约供电煤耗约3.0 g/(kW·h)。采用背压机驱动给水泵组、排汽直接用于工业供汽的汽泵改造方案,能量梯级利用程度高,节能效果较为显著;总投资较低,静态投资回收期短;安全风险可控,方案可行性高。

The higher power consumption of motor-driven feed water pump set is a common problem in coal-fired unit.The transformation of turbine-driven feed water pump combined with industrial steam supply is considered as an effective approach to solve this problem.Taking a domestic 330 MW direct air-cooled unit for example,the scheme of adding a back pressure turbine for 50%capacity feed water pump is determined based on comprehensive consideration of low load expectations and the current status of steam supply.The economics of three steam supply schemes,including combination scheme of original pressure adaptors and third-stage extraction,scheme of back pressure turbine source for feed water pump from cold section exhaust of reheating,and scheme of back pressure turbine source for feed water pump from hot section exhaust of reheating,are calculated quantitatively.The results show that,compared with the original scheme,the net coal consumption rate of scheme of back pressure turbine source from cold section exhaust of reheating decreases by 1.6 g/(kW·h)and the net coal consumption rate of scheme of back pressure turbine source from hot section exhaust of reheating decreases by 3.0 g/(kW·h).The steam pump transformation scheme of back pressure turbine driven feed water pump set and exhaust steam directly for industrial steam supply has a good energy saving effect with a high degree of energy cascade utilization,a short static payback period with a low total investment,a good feasibility with controllable security risk.