喷氨支管性能与安装对出口NO_x浓度均匀性分布的影响

Influence of performance and installation of ammonia spray branch pipes on uniformity distribution of NO_x at the exit

针对由于多样的烟道与喷氨格栅结构,在超低排放要求下,选择性催化还原(SCR)系统出现的不同运行情况,通过现场测试与调整,对典型SCR装置的性能进行分析与优化,对比分析支管安装方式对出口NO_x浓度均匀性分布的影响,并联合数值模拟对喷氨支管性能进行研究。结果表明:试验装置1在A、B两侧入口烟气速度分布相对标准偏差为12.4%与14.4%的情况下,优化前的喷氨支管结构性能与安装方式不能实现出口纵向上NO_x浓度的均匀性分布;优化后,喷氨格栅系统对横向与纵向分别进行分区喷氨控制,实现NH_3和NO_x的均匀混合,其喷氨支管出口速度相对标准偏差为6.9%。试验装置2烟气速度分布与喷氨支管出口速度分布相对标准偏差分别为27.8%与23.7%,但正确的支管安装方式,可使出口NO_x浓度分布相对标准偏差降为16.3%。

Aiming at the different performances of SCR system owing to different structures of the flue and the ammonia-injection grid under the requirements of ultra clean emissions, the performances of typical SCR devices were analysed and optimized by testing and adjustment. The influence of branch pipe installation on the uniformity distribution of NOx at the exit was contrastively analysed, and the performances of ammonia spray branch pipes studied by the numerical simulation. The results showed that the relative standard deviations（ RSDs） of inlet flue gas velocity distribution of the A, B sides of Test Device 1 were 12. 4% and 14. 4%, respectively. However, the performance and installation of the ammonia spray branch pipes before optimization could not realize in the NOx uniformity distribution in the depth direction of the exit cross section. After optimization, the partition control in the horizontal and vertical direction of the ammonia-injection grid system resulted in the uniform mixing of ammonianitrogen in Test Device 1, with the RSD of its outlet speed of 6. 9%. In Test Device 2, the RSDs of the inlet flue gas velocity distribution and the outlet velocity distribution of the ammonia spray branch pipes were 27. 8% and 23. 7%, respectively. But, the RSD of NOx on the exit cross section was 16. 3%, as a result of correct installationof ammonia spray branch pipes.