660MW机组SCR氨喷射系统故障排除及调整

SCR Ammonia Injection System Troubleshooting and Adjustment for 600 MW Unit

为解决某电厂660 MW机组运行中存在的雾化喷射器尿素流量超限、SCR出口两侧NOx排放不均、烟囱进口NOx偏低及A侧空预器漏风及其阻力较大、SCR进口喷氨不均等问题,在不同运行工况下,对SCR出口进行了多次NOx浓度分布测试及喷氨格栅的调节试验。试验发现,存在在线SCR出口NOx排放浓度严重失真、两侧氨空流量总阀开度很不合理、多根喷氨管完全堵塞等故障,经过检修及调整后,氨逃逸有明显下降。

In the operation of one 660 MW unit, problems such as urea flow rate of atomizing injector ex- ceeding limit, uneven distribution of NOx emission at the outlet of the SCR, low NOx concentration at the inlet of the chimney and high leakage and resistance of air preheater are encountered. These issues are supposed to be caused by uneven ammonia spray. To confirm this, experiments were carried out under different loads and combustion conditions. The ammonia injection grid was regulated and the correspond- ent distributions of NOx concentration at the outlet of the SCR were tested. It was found that the online monitor of the concentration of NOx emission at the outlet of the SCR was of serious distortion and that the opening of the two main valves of air - ammonia mixer at the two sides was very unreasonable. Besides, multiple ammonia spraying tubes were found to be blocked. After maintenance and adjustment, ammonia slip significantly decreased.