600 MW直接空冷凝汽器变工况特性研究

Study on VariableWorking Condition Characteristics of 600 MWDirect Air Cooling Condenser

直接空冷机组相对湿冷机组煤耗偏高,且其背压容易受环境因素影响,研究空冷凝汽器变工况下的排汽压力特性对机组安全经济运行有重要意义。采用ε-NTU法建立了600 MW直接空冷机组凝汽器变工况数学模型,计算得到了凝汽器变工况下的特性曲线,分析了迎面风速、环境温度、排汽流量对排汽压力的影响,得出如下结论:环境温度较高且排汽流量一定时,迎面风速为2.5 m/s时的背压经济性较好;夏季高温时段,凝汽器排汽压力随排汽流量的增加、迎面风速的减小而显著增大,需要机组限负荷运行,适当增加风机转速以降低背压;环境温度较低时,排汽流量和迎面风速对凝汽器排汽压力的影响较小,需要采取防冻措施,适当提高凝汽器排汽压力有利于空冷岛的安全运行。

The coal consumption of direct air cooling unit is higher than that of wet cooling unit,and its back pressure is easily affected by environmental factors.Therefore,it is of great significance to study the exhaust pressure characteristics of air condensing unit under variable working conditions for the safe and economic operation of the unit.The ε-NTU method was used to establish the mathematical model of the 600 MW direct air cooling unit under the condensing condition.The characteristic curves of the condenser under the condensing condition were calculated.The effects of the face wind speed,ambient temperature and exhaust flow rate on the exhaust pressure were analyzed.The conclusions are as follows:When the ambient temperature is higher and the exhaust steam flow is constant,the back pressure economy is better when the head wind speed is 2.5 m/s.During the period of high temperature in summer,the exhaust steam pressure of condenser increases significantly with the increase of exhaust steam flow and the decrease of head-on wind speed.It is necessary for the unit to operate under limited load and appropriately increase the fan speed to reduce the back pressure.When the ambient temperature is low,the exhaust steam flow rate and the face wind speed have little influence on the exhaust steam pressure of the condenser,so it is necessary to take anti-freezing measures.Appropriately increasing the exhaust steam pressure of the condenser is beneficial to the safe operation of the air-cooled island.