SCR系统超洁净排放调整与出口NOx均匀性分析
Ultra clean emissions adjustment and uniformity analysis of export NOx for SCR systems
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摘要: 针对典型SCR系统普遍存在的出口烟道与烟囱处NOx在线监测值不一致的问题与超洁净排放要求，选择2台流场与喷氨格栅结构不同的SCR系统进行性能与优化调整实验。通过对喷氨格栅区域烟气分布与喷氨调整前后出口烟道内NOx分布的测试，分析了导致问题的原因与调整方案的有效性以及不同喷氨格栅结构的优劣性。结果表明：喷氨格栅区域烟气流场分布与区域喷氨量的不一致性是导致不同点位NOx浓度在线监测值不一致的原因；依据调整方案能有效实现SCR出口烟道内NOx浓度均匀分布与超洁净排放的要求；改造后，能针对烟道宽度方向上烟气不均现象进行区域喷氨量调整的喷氨格栅结构Ⅱ与更均匀的烟气分布，促使调整后的2号机组A、B两侧出口NOx浓度分布相对标准偏差明显优于1号机组。Abstract: Aiming at typical SCR system common problem that the online monitoring values of NOx in the outlet flue pipes did not match the online monitoring value of NOx in the chimney and the requirement of ultra clean discharge, two SCR systems with the different flue gas flow fields and the different ammonia-injection grid structures were chosen to do the performance test and optimized adjustment test. The causes of common problem, the effects of adjustment strategies and the advantages and disadvantages of different ammonia-injection grid structures were analyzed by measuring the flue gas distribution in the areas of ammonia-injection grid and measuring the NOx distribution in the outlet flue pipes. The results showed that the common problem was caused by the amount of ammonia-injection did not match the regularity of flue gas flow field. According to the adjustment scheme, the uniform distribution of NOx concentration in the outlet flue pipes and the requirement of ultra clean discharge could be effectively realized. After promoting adjustment, the relative standard deviation of NOx concentration distribution in the outlet flue pipes of unit 2 A and B sides were significantly better than that of the unit 1.One of the reasons was the ammonia-injection grid structure Ⅱ which could efficiently adjust the amount of ammonia-injection according to the uneven distributed flue gas in the width direction. And the other reason was that the distribution of flue gas flow field was more uniform in the unit 2.
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