采用蒸发式冷却器的间接空冷系统的热经济性分析

摘要

Indirect dry cooling systems are widely used in coal-fired power plants.However,high environmental temperatures affect the heat dissipation performance of the dry cooling tower,causing the increase of the back pressure of the steam turbine.In this work,the evaporative cooler operating with the dry cooling tower is adopted to reduce the circulating water temperature and the exhaust steam pressure,and improve the thermal efficiency of the power unit.Taking a 600-MW steam turbine unit as the study object,an indirect dry-cooled system with evaporative cooler is designed and a mathematical model is established.The matching characteristics of the heat load distribution between the evaporative cooler and the dry cooling tower are analyzed.The back pressure,the water consumption and the pump power consumption are analyzed for various heat loads.The results show that at the rated load,when the ratio of the water flow rate for the evaporative cooler to the total circulating water flow rate is between 0.21 and 0.31,and the generation standard coal consumption rate decreases by about 7.4 g/(kW·h).%间接空冷系统在中国的应川越来越广泛,但是高温天气影响空冷塔散热,导致汽轮机背压升高.采用蒸发式冷却器与闭式空冷塔并联运行,可以降低循环水温度,进而降低汽轮机的排汽压力,提高机组的热经济性.针对某600 MW汽轮机组,设计了一种采用蒸发式冷却器的问接空冷系统,构建了数学模型,分析了蒸发式冷却器与闭式空冷塔的热负荷匹配特性,探讨了额定工况下蒸发式冷却器热负荷改变时,汽轮机背压、系统耗水量和冷却系统功耗的变化规律.计算结果表明,额定工况下,分流比为0.21～0.31时,发电标准煤耗率可降低7.4 g/(kW·h).