加氢装置分馏重沸炉出口管线腐蚀原因分析及预防

Cause analysis and prevention of corrosion in outlet pipeline of fractionation reboiler in hydrogenation unit

某石化公司柴油加氢装置在运行5 a后发现分馏重沸炉出口管线发生腐蚀减薄。为保障装置安全生产,分析管线减薄原因,对装置进行了停工检修,并对减薄管线进行检测分析。对腐蚀管线内壁进行宏观分析,发现管线减薄均匀,弯头外弯处有冲刷痕迹,判断管线发生了均匀腐蚀和冲刷腐蚀。进行金相分析,发现送检样品材质符合20号钢材质要求,判断腐蚀原因不是本体材质缺陷。进行电镜分析,发现送检样品腐蚀处O,S和Fe三种元素含量较高,判断腐蚀处含有铁的硫化物和氧化物,符合高温硫腐蚀的特征。分析其腐蚀机理后,确定了其腐蚀类型是高温硫腐蚀和冲刷腐蚀,提出了管线材质升级、扩径改造和控制原料油参数等防护措施。

After 5 years of operation,corrosion thinning occurred in the outlet pipeline of fractionation reboiler in hydrogenation unit,which seriously affects the stable production of unit.To ensure the safe production of the unit,it was shut down for maintenance,and then thinning pipeline was inspected and analyzed.Macroscopic analysis was conducted on the inner wall of the corroded pipeline,it is found that the pipeline was uniformly thinned and there were erosion marks at outer bend of the elbow,indicating that the pipeline had undergone uniform corrosion and erosion corrosion.Metallographic analysis revealed that the sample material submitted for inspection meets the requirement of No.20 steel material,it is confirmed that body material defects is not the cause of corrosion.Electron microscopy showed that the corrosion site of the submitted sample contains high level of O,S and Fe elements.It is determined that the corrosion site contained iron sulfides and oxides,which is consistent with the characteristics of high-temperature sulfur corrosion.The analysis of corrosion mechanism discovered that the corrosion types are high-temperature sulfur corrosion and erosion corrosion.Protective measures were proposed such as upgrading pipeline material,enlarging diameter and controlling raw oil parameters.