空冷凝汽器全工况运行特性分析

Performance Analysis of Air-cooled Condensers at All Operating Conditions

掌握火电站空冷凝汽器在各种工况下的运行特性,对于提高我国直接空冷机组的运行水平具有重要意义。以300MW直接空冷机组空冷凝汽器为例,分析了反映机组运行性能的汽轮机背压的影响因素。针对轴流风机全速和半速运行工况,计算得到了汽轮机背压随凝汽器凝结蒸汽量和进口空气温度的变化规律。结果表明:随凝汽器凝结蒸汽量和进口空气温度的增加,汽轮机背压增加;随轴流风机风速升高,汽轮机背压降低。轴流风机运行方式的调整,依赖于环境温度和机组热负荷的变化。对于冬季低温运行的空冷凝汽器,为防止出现汽轮机背压低于阻塞背压和凝汽器管束冻裂,风机需减速运行。反之,在夏季高温条件下运行的空冷凝汽器,为避免汽轮机背压过高带来的非正常停机和机组运行经济性的下降,风机需全速甚至超设计风量运行。

It is of great importance to investigate the performance of air-cooled steam condensers at various operating conditions for the running improvement of the direct air-cooled units in China. Based on the air-cooled condenser of a 300MW unit, the factors that affect the exhaust steam pressure were analyzed. The variations of the exhaust steam pressure with saturated exhaust steam flow rate and the inlet air temperature of the condenser were presented at 100% speed and half speed of axial fans. The results show that the exhaust steam pressure increases with the saturated exhaust steam flow rate and the inlet air temperature increasing and it decreases with the axial fan speed increasing. The regulation of the fan depends on the ambient air temperature and the heat load of the condenser. For the air-cooled condenser operating in cold winter, the fan should run at a low speed to ensure that the exhaust steam pressure was not smaller than the blocking pressure and to prevent the condenser tube banks from freezing. For the air-cooled condenser running in hot summer however, the fan should run at 100% or more than 100% speed to avoid the abnormal shutting down and the bad economy of the unit due to high exhaust steam pressure.