某亚临界锅炉过热器管腐蚀泄漏原因

Reasons for corrosion and leakage of superheater tubes in a subcritical boiler

某亚临界锅炉末级过热器发生爆管事故。采用宏观观察、力学性能测试、金相检验、扫描电镜及能谱分析、X射线衍射分析等方法对过热器爆管原因进行分析。结果表明:过热器管内表面产生氧化皮,引起管壁局部过热;氧化皮达到一定厚度并脱落,堆积在下部弯头位置,导致蒸汽流通截面积减小、流速下降,进一步引起管壁温度上升,管子材料出现劣化,且力学性能下降,甚至发生高温蠕变损伤和壁厚减薄,在高温环境和蒸汽压力的综合作用下,最终过热器发生爆管事故。

A tube burst accident occurred in the final stage superheater of a subcritical boiler.The causes of superheater tube bursting were analyzed using macroscopic observation,mechanical property testing,metallographic examination,scanning electron microscopy and energy spectrum analysis,X-ray diffraction analysis.The results show that oxide scale was generated on the inner surface of the superheater tube,causing local overheating of the tube wall.The oxide scale reached a certain thickness and fell off,accumulated at the lower elbow position,resulted in a reduction in steam flow cross-section area and a decrease in flow velocity,further caused an increase in pipe wall temperature.The materials of pipe deteriorated,coupled with a decreased in mechanical properties,even resulted in high temperature creep loss and wall thickness recluction,and ultimately led to tube burst accident of the superheater under the combined effect of high temperature environment and steam pressure.