板式蒸发式凝汽器在300MW直接空冷机组中的应用

Application of plate evaporative condenser on a 300MW direct air-cooling unit

针对直接空冷机组在夏季时背压偏高、出力受限的问题,提出采用板式蒸发式凝汽器分流部分汽轮机排汽,以降低空冷岛热负荷,从而降低机组背压.以某300 MW直接空冷机组为例进行上述技术改造.改造后机组运行结果表明：额定负荷工况、环境温度30℃下,投运板式蒸发式凝汽器系统后,机组背压由33．47 kPa 降至29．05 kPa,达到了额定工况下,对机组背压的要求（设计值30 kPa）；TRL工况、环境温度30℃下（湿球温度为17．68℃）,板式蒸发式凝汽器系统冷凝能力为50．11 t/h,机组背压较投运前降低4．1 kPa；板式蒸发式凝汽器的水耗率为0．7~0．8；板式蒸发式凝汽器系统的运行效果随着环境温度的升高而提高；板式蒸发式凝汽器的冷凝量和补水流量随着外部空气湿度的增大而减小,且趋势相同,空气湿度增大到一定程度后,其冷凝量和补水流量趋于定值.

In summer,the direct air cooling units will suffer high back pressure and its output power will be insufficient.Against this problem,the plate evaporative condensing system was proposed to diverge part of the turbine exhaust steam and reduce the heat load of air cooling island,thus the unit operating back pres-sure can be decreased.Taking a 300 MW direct air cooling unit as the example,the retrofitting was carried out.The operation results show that,under condition with rated load and ambient temperature of 30 ℃,af-ter the plate evaporative condensing system was put into service,the unit back pressure decreased from 33. 47 kPa to 29.05 kPa,satisfying the requirements under rated condition （30 kPa）.Under the TRL condition and at ambient temperature of 30 ℃ （the wet bulb temperature of 17.68 ℃）,the condensing ability of the plate evaporative condensing system was 50.11 t/h,and the unit back pressure decreased by 4.1 kPa.The water consumption rate of the plate evaporative condensing system was 0.7 to 0.8.The operation effect of the plate evaporative condensing system got better with an increase in the ambient temperature.As the hu-midity of the ambient air increased,both the steam flow and supplement circulating water flow decreased and with the similar trend.When the air humidity climbed to a certain value,the steam flow and supple-ment circulating water flow approached to a definite value.The results show the retrofit meets the design requirements and the system runs stably.