乙烯裂解炉炉管的熔融腐蚀破坏

摘要

熔融腐蚀是乙烯裂解炉辐射段炉管在使用中常发生的一种破坏形式,文章通过宏观检验、光谱分析、扫描电镜及能谱、金相组织、原料含硫量调查、结焦、烧焦工艺分析,得出了某乙烯装置裂解炉炉管的熔融失效原因:炉管表面局部产生结焦、碱金属盐等形成低熔点共晶物、碱金属离子催化燃烧作用加之烧焦过程空气流量和温度控制的影响,使炉管表面形成过热点,局部温度超高,保护膜破坏发生熔蚀,同时渗碳、氧化、蠕变以及介质冲刷共同作用,造成炉管短期内局部腐蚀损坏泄漏.防止熔融腐蚀破坏的措施是控制裂解炉烧焦时炉管出口温度COT,加强添加结焦抑制剂,控制原料、稀释蒸汽等物料中碱金属离子含量以及对裂解炉烧焦加强巡检.%Fusion corrosion is a failure mode that often occurs when the ethylene cracking furnace tube is used. Through macroexamination, spectral analysis, scanning electron microscope (SEM), energy spectrum, metallographic structure, investigation of sulfur content of the material, process analysis of coking and coke burning, this paper found out the fusion failure causes for an ethylene cracking furnace tube. A conclusion was reached that the coke locally formed on tube surface at first and alkali metalssalts in blends can produce a low - melting eu-tectic mixture. Alkali metals ions have positive functions in coke catalytic combustion. In addition, coking air flow and temperature generate over- heat point, the protective film was de-structed in high temperature,then fusion corrosion happened. At the same time, carburization,oxidation, creep and medium erosion work together to cause the leakage of the tube in a short period. Some measures to prevent fusion corrosion damage cover controlling the COT, adding inhibitors, controlling alkali metal ion contents in medium and strengthening inspection tour for the coking of cracking furnace.