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

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