燃煤耦合污泥发电机组电除尘器腐蚀诊断

Diagnosis on Electrostatic Precipitator Corrosion of Coal-fired Coupled Sludge Generator Set

某火力发电厂2台1 000 MW燃煤耦合污泥发电机组,电除尘器的极板和极线被积灰覆盖,腐蚀严重,使用寿命缩短。通过检测极板和极线上的积灰与腐蚀产物,同时结合污泥掺烧、设备运行调查情况,对腐蚀机理及原因进行了分析。结果表明:机组掺烧污泥后,脱硝催化剂严重积灰、磨损,导致氨逃逸率持续偏高,氨逃逸生成的硫酸氢铵、硫酸铵等强酸性盐在极板和极线表面产生黏性沉积,该灰垢吸湿潮解,形成强酸性电化学腐蚀环境,造成金属严重腐蚀;入炉煤的碱金属、氯含量较高,颗粒态氯盐随黏性灰沉积在极板和极线上,促进了电化学腐蚀。

In two 1 000 MW coal-fired coupled sludge generator sets of a thermal power plant,the plate and pole line of the electrostatic precipitator were covered by ash deposition,which was seriously corroded and the service life was shortened.The corrosion mechanism and causes were analyzed by detecting the ash deposition and corrosion products on the plate and pole line,combined with the sludge blending and equipment operation investigation.Results show that,after the unit is mixed with sludge,serious ash deposition and wear of denitration catalyst lead to high ammonia escap erate.Strong acidic salts such as ammonium bisulfate and ammonium sulphate generated by ammonia escape are viscous deposition on the surface of the plate and pole line,which absorbs moisture and then deliquescent,forming a strong acidic electrochemical corrosion environment and causing serious corrosion of metals.The alkali metal and chlorine content of the coal into the furnace are high,and the granular chlorate is deposited on the plate and pole line with the viscous ash,which aggravates electrochemical corrosion.