墙式再热器管内壁腐蚀原因及其预防措施

Causes Analysis of Inner Wall Corrosion of Wall Reheater Pipe and Preventive Measures

某电厂300MW亚临界燃煤机组墙式再热器管发生了腐蚀穿孔现象。通过宏观检验、X射线荧光光谱分析、金相检查、扫描电镜及能谱检测等手段对腐蚀原因进行分析。结果表明:锅炉本身结构及停炉保护不当造成机组停运时少量冷凝水残留在穿墙管弯头及水平段底部,导致管内壁发生溶解氧腐蚀,最终腐蚀穿孔。针对上述事件,某发电集团对区域内机组进行排查,并从停炉操作过程、停备保护方法、水汽品质控制、日常检修维护等方面提出一系列预防措施。

Corrosion and perforation occurred in a wall reheater pipe of a 300MW subcritical coal-fired unit in a power plant.The corrosion causes were analyzed by means of macroscopic examination,X-ray fluorescence spectroscopy,metallographic examination,scanning electron microscopy and energy dispersive spectroscopy.The results showed that when the unit was out of operation,a small amount of condensed water remained at the bottoms of the wall-through elbow and horizontal section duo to the boiler structure and improper boiler shutdown protection,resulting in dissolved oxygen corrosion of the inner wall of the pipe and eventual corrosion perforation.In view of the above incident,a power generation group investigated the units within the area,and proposed a series of preventive measures from the aspects of furnace shutdown operation processes,shutdown protection methods,water vapor quality control,daily maintenance and other aspects.