涡流混合式SCR脱硝系统喷氨优化调整试验研究

针对脱硝系统氨逃逸量大造成除尘器无法投运的问题,对涡流混合式脱硝系统进行喷氨优化试验。试验发现,脱硝出口NOx浓度在烟道宽度方向分布不均。通过调整喷氨支管手动蝶阀降低了脱硝出口NOx浓度分布的不均匀度。满负荷下,烟道A侧出口不均匀度由48.3%降低到19.4%;B侧出口不均匀度由62.7%降低到21.8%。经过调整,NOx分布不均匀度显著下降。两侧烟气流量在高低负荷下不存在明显的偏差,流场分布也较为均匀。电厂采用新型涡流静态混合器,有助于解决脱硝出口NOx浓度沿烟道深度方向分布不均的问题。利用SIS数据分析发现脱硝出口NOx浓度CEMS测点不准确,导致喷氨自动投运时喷氨量过大,氨逃逸量变大。CEMS测点取样不具代表性,建议采用网格法取样,并对CEMS测点进行定期标定。喷氨控制策略中,喷氨量跟随性差,导致喷氨量与脱硝入口NOx浓度变化存在一定的延迟,建议优化喷氨控制逻辑。净烟气NOx排放浓度值不宜设置得过低,设定值越低,氨逃逸量越大。综合环保性和经济性,推荐净烟气NOx排放浓度控制在25~35 mg/m3。经过喷氨优化后,整体的氨逃逸量控制在3×10^-6以下。

Experimental study on optimization adjustment of ammonia injection in vortexmixer SCR denitrification system

Considering the problem that the dust collector could not be put into operation due to the large amount of ammonia escaping from the denitrification system,the optimization adjustment of ammonia injection in vortex mixer SCR denitrification system was carried out.It is found that the NO x concentration in the denitration outlet is unevenly distributed in the width direction.By adjusting the manual butterfly valve of the ammonia injection branch pipe,the non-uniformity of NO x concentration in the denitration outlet is reduced.At full capacity,the inhomogeneity of A side of the flue decreases from 48.3%to 19.4%,the inhomogeneity of B side decreases from 62.7%to 21.8%.After adjustment,the NO x distribution inhomogeneity decreases significantly.There is no obvious deviation of flue flow on both sides under high and low load.The distribution of flow field is relatively uniform.A new type of eddy current static mixer was adopted whcih was helpful to solve the problem of uneven distribution of NO x concentration in the outlet of denitration along the depth direction.It is found from the SIS data that the CEMS measuring point of NO x concentration at denitrification outlet is inaccurate,which leads to the excessive amount of ammonia spray and the large amount of ammonia escape during automatic operation of ammonia injection.The measuring point of CEMS is not representative,which is recommended to use grid sampling method.A regular calibration of CEMS measuring points is recommended.The poor following performance of ammonia spray causes a certain delay between the ammonia spray and the NO x concentration at the denitrification inlet in control strategy of ammonia injection.The ammonia spray control logic should be optimized.The NO x emission concentration of net flue gas should not be set too low.The lower the setting value is,the greater the ammonia escape amount is.Considering the environmental requirements and economy,it is recommended that the net flue gas NO x emission concentration is controlled within 25-35 mg/m 3.After the ammonia injection optimization,the overall ammonia escape is controlled below 3×10-6.