Abstract: In order to solve the overheating problem of the 5^# boiler exhaust gas for the direct air cooling 600 MW unit in a power plant, this paper proposed the technical solution by installing low-temperature economizer. Flue gas heat was used to heat the condensed water in this process. Extraction steam was routed back to the steam turbine to continue expanding, the power of steam turbine was increased, the turbine heat rate and the gross coal consumption rate were decreased. Condenser vacuum fell by1.617kPa after low-temperature economizer was added. Using the habitual thermal balance method and equivalent enthalpy drop method, the thermal economic of the designs was evaluated. The habitual thermal balance method's results indicated that after the low-temperature economizer was added, the heat rate decreased by 25.711kJ/(kW·h) , the gross coal consumption reduced by 0.959g/(kW·h);and the equivalent enthalpy drop method's results indicated that the low-temperature economizer made turbine heat rate decrease by 26.832kJ/(kW·h) and reduced the gross coal consumption by 1.001g/(kW·h). That adding low-temperature economizer achieved good energy saving results. Also proved that the consistency of the equivalent enthalpy drop method and the habitual thermal balance method.

Key words: low-temperature economizer, condenser vacuum, habitual thermal balance method, equivalent enthalpy drop method, heat rate, gross coal consumption

摘要： 为解决国内某电厂600MW直接空冷机组5^#锅炉排烟温度过高的问题,在锅炉尾部烟道加装低温省煤器,利用烟气余热加热机组凝结水。抽汽被排挤回汽轮机继续膨胀做功,增加汽轮机发电功率,降低汽轮机热耗和机组发电煤耗;同时汽轮机排汽量增加,凝汽器真空下降,机组热经济性变差。本文以TRL工况为例,对该电厂加装低温省煤器后进行了计算,得出凝汽器真空下降1.617kPa。利用热平衡法与等效焓降法,对加装低温省煤器后机组热经济性进行计算。最终结果为:热平衡法得到加装低温省煤器后汽轮机热耗下降25.711kJ/(kW·h),机组发电煤耗降低0.959g/(kW·h);等效焓降法得到,加装低温省煤器后汽轮机热耗下降26.832kJ/(kW·h),机组发电煤耗降低1.001g/(kW·h)。说明加装低温省煤器具有良好的节能效果,同时也证明了等效焓降法与常规热平衡法的一致性。

关键词: 低温省煤器, 凝汽器真空, 热平衡法, 等效焓降法, 热耗, 发电煤耗