燃煤电厂超低排放改造后烟道氯化铵结晶原因分析及对策

摘要

After the ultra-low emission transformation,the contaminants emission limits of coal-fired power plants are reduced hugely and the statuses of emission reduction equipment are getting worse simultaneously.Hence,new operation problems have appeared in the flue gas purification equipment.Crystallization problem has taken place in the flue system of some coal-fired power plants,such as on the surface of bag filter clean room,induced draft fan hub,FGD inlet flue and so on.The results of the crystal analysis show that the main component of crystalline is ammonium chloride,which is up to 90％.In this study,the crystallization reaction mechanism of ammonium chloride was studied and calculated.The results show that the crystallization temperature of ammonium chloride is about 75-115 ℃.Therefore,the crystallization problems of ammonium chloride could be found in the dust separator,induced draft fan and GGH.The crystallization of ammonium chloride could not only clog the equipment,but also corrode the surfaces of the flue system.According to the actual operation situation,some prevention and control measures are proposed.And this paper suggested to reduce the concentrations of ammonia and hydrogen chloride in the flue gas to avoid the crystallization problem of ammonium chloride.%燃煤电厂超低排放改造之后,由于污染物排放限值的降低和治理设备运行压力的增加,机组烟气净化设备出现了新问题.部分电厂除尘器净烟室、引风机风道、脱硫系统入口烟道等位置集中出现大量白色结晶物,实验室化验分析得知该结晶物主要成分90％以上为氯化铵,对氯化铵结晶反应的机理进行了研究和计算.结果表明:烟道内氯化铵开始发生结晶的温度为75～115℃,即空气预热器出口至脱硫系统入口之间的区域,该区域包含除尘器、引风机、或气气再热器(GGH)等重要辅机设备;氯化铵结晶不但会堵塞设备,还会严重腐蚀烟道壁面等部位;提出日常运行过程中的预防和控制措施,以及控制烟气中逃逸氨质量浓度和氯化氢质量浓度等建议.