大型火电机组SCR脱硝系统现场调试若干关键问题研究及应用

针对某电厂1、2、3号锅炉选择性催化还原法（selective catalytic reduction,SCR）脱硝系统现场调试过程中遇到的技术难题,进行了研究并得到工程应用。分析了稀释风机联锁保护、氨–空气混合器关断阀的联锁保护、供氨调节阀自动控制等方面存在的技术难题,并提出相应的解决方法。主要结论如下：氨–空气混合器前关断阀应加入到联锁保护逻辑中；为防止当供氨压力低时,如果供氨管道上逆止阀工作不正常则可能存在稀释风向供氨管道内倒灌空气而引起不安全因素,在氨–空气混合器关断阀的联锁保护关闭条件中添加此项逻辑联锁保护条件；脱硝系统自动控制以跟踪出口NOx 含量为依据,建议运行人员在脱硝系统满足环保投运要求的条件下,尽量根据入口NOx 含量变化情况及时调整系统脱硝率,减少出现脱硝率过高的情况。

Research and Application on Some Key Problems in Field Commissioning of SCR Denitration System of Large-scale Thermal Power Unit

Aiming at technical difficulties in field commissioning process of selective catalytic reduction denitration system of No.1 ,No.2 and No.3 boilers in some power plant,research and engineering application was conducted. Technical difficul-ties in dilution fan interlock protection, interlock protection of shut-off valve of ammonia-air commingler and automatic control of ammonia supply adjusting valve were analyzed and relevant solutions were proposed. Main conclusions were as fol-lows：front shut-off valve of ammonia-air commingler should be added in interlock protection logic,for preventing unsafe factors caused for reason of air flow backward into the ammonia supply pipe by dilution wind resulted from abnormal action of upward check valve on ammonia supply pipe when ammonia supply pressure was low,this logic interlock protection con-dition was to be added in interlock protection shut-down conditions for shut-off valve of the ammonia-air commingler. On the basis of NOx content at the exit for automation control of denitration system,operation crews were suggested to adjust denitration ratio in time according to changes of NOx content at the entrance and reduce situation of higher denitration ratio under the condition of denitration system meeting requirement for environmental protection operation.