丙烯腈反应气体冷却器换热管的腐蚀失效原因  

Corrosion Failure Reason of the Heat Exchange Tube of a Acrylonitrile Reaction Gas Cooler

作　　者：陈维 路宝玺 肖磊 袁明峰 施玉琦 许永锋 CHEN Wei;LU Baoxi;XIAO Lei;YUAN Mingfeng;SHI Yuqi;XU Yongfeng(Shanghai Secco Petrochemical Co.,Ltd.,Shanghai Chemical Industry Zone,Shanghai 201507,China)

机构地区：[1]上海市化学工业区上海赛科石油化工有限责任公司,上海201507

出　　处：《腐蚀与防护》2020年第5期57-62,共6页Corrosion & Protection

摘　　要：某石化公司丙烯腈生产装置反应气体冷却器,运行仅数月就发现管板和换热管束端口发生严重的局部腐蚀等失效缺陷。现场取样,采用光学显微镜、扫描电镜(SEM)、能谱仪(EDS)等重点分析了缺陷处的腐蚀形貌和产物,并对工艺介质化学特性进行全面检测分析;利用有限元模拟分析管板与换热管的温度场。结果表明,换热管内壁距离管板约17~25cm的位置严重腐蚀减薄,其机理为H2SO4露点腐蚀;H2SO4的来源是喷射固体颗粒,其内部含有的(NH4)2SO4,在高温环境(约440℃)会分解出SO2,SO2与残余O2、H2O(气)进一步反应生成H2SO4。Severe defects such as severe localized corrosion of tubesheets and heat transfer tube bundle ports were found in a reaction gas cooler of an acrylonitrile production unit in a petrochemical company after only a few months of operation.Samples were collected on the spot,and the corrosion morphology and products at the defects were analyzed using optical microscope,scanning electron microscope(SEM),and energy spectrometer(EDS),and the chemical properties of the process media were comprehensively analyzed.Finite element simulation was used to analyze the temperature field of the tube sheet and the heat exchange tube.The results show that the inner wall of the heat transfer tube was severely corroded and thinned at a distance of about 17 to 25 cm from the tube sheet,and the mechanism was H2SO4 dew point corrosion.H2SO4 originated from sprayed solid particles.The(NH4)2SO4 contained in the interior of the particles decomposed to generate SO2 in a high-temperature environment(about 440℃),which further reacted with residual O2,H2O (gas)to generate H2SO4.

关 键 词：换热器 露点腐蚀 失效分析 15CrMoG (NH4)2SO4 

分 类 号：TG172.3[金属学及工艺—金属表面处理]