Research On Change Law Of Water Loss And Method Of Water-saving In Power Plant Circulating-water System

The water consumption of circulating-water system in power plants occupies a great proportion of the total water consumption and the evaporation loss of cooling tower is the maximum water loss in circulating-water system. Water-saving techniques of cooling water system can not only save a large amount of water resource, but also reduce the discharge of sewage and protect the environment. Therefore research on the change law of evaporation loss and measures to reduce the water consumption of circulating cooling water system is of much practical significance.This paper takes a certain natural draft counter-flow wet cooling tower of 300MW generating unit for example and studies the change law of evaporation loss with inlet water temperature and inlet water flow on most summer and winter condition, using the calculation model of evaporation loss. The results of calculation shows:firstly, when inlet water temperature decreases and the other parameters keep constant, the evaporation loss decreases both on summer and winter condition. Secondly, when inlet water flow decreases and inlet water temperature keeps constant, the evaporation loss decreases both on summer and winter condition if the cooling tower is taken as the research object. However, when taking the whole cold end system as research object, the evaporation loss does not change greatly with circulating water flow. So it is impossible to decrease the evaporation loss by simply reducing the circulating water flow without changing the circulating-water system.The change of inlet water temperature and inlet water flow can be considered as the variation of inlet water heat. This paper studies the change law of evaporation loss with inlet water heat. The result shows that the evaporation loss decreases when inlet water heat decreases, based on which, this paper proposes a new method to reduce the water consumption of circulating-water system by reducing the evaporation loss with the alteration of the cooling water system and the decrease of inlet water heat.This paper provides two possible arrangements of heat pipe heat exchanger in the reformation of cooling water system and studies the influence to the inlet water temperature of condenser. It shows that the inlet water temperature is lower after reformation for the tandem arrangement and may be higher for the parallel arrangement. This paper also analyzes the water saving effect of the different arrangements and finds that the more heat exchanged in the heat pipe heat exchanger, the better water saving effect will achieved for both tandem and parallel arrangements. The amount of water saved increases with the decrease of temperature drop in heat pipe heat exchanger for the parallel arrangement. This paper takes a 300MW generating unit for example and conducts design calculation of heat pipe heat exchanger. According to the calculation result, the reformation can get better water saving effect in winter condition compared with the summer condition.Research results of this subject lay a theoretical foundation for water-saving of circulating-water system. The method of decreasing inlet water heat by a heat pipe heat exchanger in order to reduce the evaporation loss presents a new way of water-saving in cooling water system.