给水置换式省煤器系统在电站锅炉中的应用

Application of an Economizer System with Feedwater Redistribution in a Utility Boiler

将给水置换式省煤器系统运用到电站锅炉低负荷下SCR安全投运的改造中,将部分温度较低的工质水直接引流到下降管中,同时将部分省煤器出口温度相对较高的热水置换到省煤器入口。结果表明:通过给水置换的方式可提高省煤器实际入口工质水的温度,减小省煤器的传热温压,减少省煤器的换热量,提高省煤器出口的烟气温度,即提高了脱硝设备入口的烟气温度,达到了在低负荷下安全投运脱硝设备的目的;改造后锅炉可在低负荷下安全稳定运行,因脱硝设备不能投运而产生的NOx排放量也减少。

To put the SCR system into safety operation at low load of a utility boiler, a retrofit scheme was proposed by adopting the economizer system with feedwater redistribution, where a part of low-tempera- ture feedwater is bypassed directly to the downcomer, and a part of hot water is recirculated from the econ omizer outlet to the inlet. Results show that the economizer system with feedwater redistribution can help to improve the inlet tempemperature of working medium in the economizer, reduce the heat-transfer tem- perature difference, reduce the quantity of heat transfer, and improve the flue gas temperature at economi zer outlet, i.e. improve the flue gas temperature at SCR inlet, thus achieving safety operation of the SCR facility during low load operation of the boiler. After retrofit, the boiler is now able to operate safely and stably, and the NO, emission is reduced accordingly due to the SCR unit coming into use.