燃煤电厂水平衡模型与节水分析

随着水资源的日益短缺和火电装机容量的持续增加，应用节水技术是目前火电行业可持续发展的重要途径。基于煤种、气象条件和电厂性能参数，提出了电厂水平衡模型，绘制了电厂水流图，直观体现了进入和离开电厂的水平衡关系，辨析系统节水的关键环节。定量分析了烟气余热及水分回收系统的节能和节水效果。以燃烟煤的超临界机组为例，在离开电厂的水流中，冷却塔蒸发、风吹损失占60%，冷却塔排污占20%，排烟中水分占15%。火电厂节水的重点在于冷却系统、废水排放和排烟水分回收。针对火电厂余热和水分回收的系统，理论计算表明：对于湿冷机组，如果烟气水分回收60%，则超临界机组单位供电量耗水量下降19.2%；对于空冷机组，如果烟气水分回收60%，则电厂的取水量为零；如果同时采用半干法或干法脱硫系统，则电厂可以成为供水方。

Water Balance Model and Water-Saving Analysis for Coal-fired Power Plants

With the increasing shortage of water resources and the continuous increase of thermal power installed capacity, the application of water-saving technology is an essential issue for the sustainable development of the thermal power industry. The water balance model and water flow diagram is proposed based on coal type, meteorological conditions, and power plant performance parameters. From the water flow diagram, the water balance relationship is intuitively reflected between entering and leaving streams. The key processes to reduce system water use were identified. The energy and water-saving effects of flue gas waste heat and water recovery system are quantitatively analyzed. For supercritical power plant burning bituminous coal, about 60% water losses come from cooling tower evaporation and wind blowing, while cooling tower blowdown accounts for 20%. The moisture content in exhaust fluegas accounts for 15%. The critical points of water saving in thermal power plants are cooling systems, wastewater discharge, and moisture recovery from flue gas. This paper presents a waste heat and moisture recovery from flue gas system. The preliminary analysis shows that, for wet-cooled units, the water consumption per MW·h will drop by 19.2% with flue gas moisture recovered by 60%. For air-cooled units, if the flue gas moisture is recovered by 60%, the water withdraw of the power plant will be zero. If the semi-dry or dry desulfurization system is adopted at the same time, the power plant can become the water supplier.