超低排放形势下SCR脱硝系统运行存在问题与对策

Difficulties and countermeasures of SCR denitration system operation in ultra low emission situation

针对超低排放形势下选择性催化还原(SCR)脱硝系统运行过程中出现的NO_x排放超限、空气预热器硫酸氢铵堵塞加重等问题,分析其主要与超低排放对SCR反应器中NH3/NO_x分布的均匀性要求提高,SO_2/SO_3转化率升高,喷氨优化控制要求提高,最低喷氨温度升高及催化剂寿命管理更加复杂等有关。对此,提出了通过喷氨优化调整和流场优化改造改善NH3/NO_x分布均匀性,减少催化剂的用量及钒含量控制SO_2/SO_3转化率,降低脱硝系统入口喷氨量、SO_3质量浓度或设备改造来拓宽低负荷脱硝运行范围,通过喷氨控制系统优化降低NO_x排放超标及过量喷氨的风险,采取有效的催化剂寿命管理延长催化剂使用寿命、降低废催化剂产生量等解决方案。对实现燃煤电厂SCR脱硝系统的安全、高效及经济运行具有指导意义。

Against the frequent NOx emission overrunning and increasingly air preheater ammonium bisul- fate （ABS） blocking in the ultra low emission situation,reason analysis was carried out and the reasons are considered as the followings,the improved requirement of the NH3/NOx mixing uniformity, the increased SO2 to SO3 oxidation rate, the higher requirement of denitration control system, the improved minimum am- monia injection temperature and more difficulty with management catalyst life, and so on. To solve these problems,several countermeasures were put forward, such as adjusting the ammonia injection grid to im- prove the distribution uniformity of NH3/NOx,reducing the amount of catalyst and vanadium proportion to control the SO2/SO3 oxidation rate,decreasing the ammonia injection quantity, SO3 concentration or by e- quipment modifications to broaden the scope of low load operation, performing ammonia injection control system optimization to reduce the NOx emission overrunning and the risk of excessive spraying ammonia, prolonging the service life of the catalyst and reducing the amount of spent catalyst through effective cata- lyst management, All of these can provide guidance for realizing safety, economic and efficient operation of the SCR equipment in coal-fired power plants.