某燃煤电厂电除尘器积灰原因研究

Study on the cause of dust accumulation of electrostatic precipitator in a coalfired power plant

为解决某燃煤电厂电除尘器二次电流下降,出口粉尘浓度增大,除尘效率降低问题,分析电除尘器极板极线积灰成分,结合机组运行及喷氨情况,分析积灰形成原因。结果表明:除尘器灰样主要成分为可燃物、SO_(3)、TiO_(2)、Al_(2)O_(3)和氨离子,B侧电除尘器阳/阴极积灰中SO_(3)、铵离子质量占比分别为20.84%/20.35%,7.33%/8.22%,高于A侧电除尘器阳/阴极灰样中SO_(3)(10.54%/4.25%)、铵离子(1.79%/0.58%)含量占比,且B除尘器灰样微观结构更为致密。结合机组运行情况及机组检修时B侧空预器元件进行了更换而A侧没有更换、B侧处理烟气量明显大于A侧的实际情况分析,得出结论认为由于B侧处理烟气量大、脱硝烟气分布不均、脱硝出口NO_(x)浓度增大,为降低B侧脱硝出口NO_(x)浓度而过量喷氨,导致B侧生成的硫酸氢氨增多,硫酸氢氨吸附飞灰粘附在除尘器极板极线上,B侧除尘器极板极线积灰更加严重。建议在同步更换A侧空预器元件、优化脱硝烟气流场分布的基础上加强运行调整,保证喷氨均匀性,减少除尘器积灰。

In order to solve the problem that the secondary current of the electrostatic precipitator in a coal-fired power plant decreases,the outlet dust concentration increases,and the dust removal efficiency decreases,the ash deposition composition of the polar plate of the electrostatic precipitator is analyzed,and the causes of ash deposition are analyzed in combination with the unit operation and ammonia injection.The results show that the main components of the precipitator dust sample are combustibles,SO_(3),TiO_(2),Al_(2)O_(3)and ammonia ions.The mass ratios of SO_(3)and ammonium ions in the positive/cathode dust of the B-side electrostatic precipitator are 20.84%/20.35%and 7.33%/8.22%,respectively,which are higher than those of the positive/cathode dust of the A-side electrostatic precipitator.The proportion of SO_(3)(10.54%/4.25%)and ammonium ions(1.79%/0.58%)in the dust sample,and the microstructure of the dust sample of the B-side electrostatic precipitator is more dense.Combined with the actual situation of unit operation and unit maintenance,the B-side air preheater element was replaced while the A-side was not replaced,and the amount of flue gas treated on the B-side was significantly larger than that on the A-side.It is concluded that due to the large amount of flue gas treated on the B-side,the uneven distribution of denitration flue gas,and the increase of NO_(x)concentration at the denitration outlet,excessive ammonia injection is carried out to reduce the NO_(x)concentration at the denitration outlet on the B-side,resulting in the increase of ammonia hydrogen sulfate generated on the B-side.The fly ash adsorbed by ammonia hydrogen sulfate adheres to the plate electrode of the dust collector,and the dust accumulation on the plate electrode of the dust collector on the B-side is more serious.It is recommended to strengthen the operation adjustment on the basis of synchronously replacing the A-side air preheater components and optimizing the distribution of the denitration flue gas flow field,so as to ensure the uniformity of ammonia injection and reduce the dust deposition of the dust collector.