渣油加氢空冷系统流动腐蚀风险预测及防控策略研究

Flow corrosion risk prediction and control strategy in residual oil hydrotreating air cooler systems

针对某石化企业I、II系列渣油加氢空冷系统,基于工艺过程的关联分析,采用逆序倒推法构建工艺仿真模型,阐明流动-传热-相变环境下铵盐结晶腐蚀和多相流冲蚀机理,确定将腐蚀因子Kp、流速、硫氢化铵(NH4HS)浓度等作为控制加氢空冷系统流动腐蚀的关键参数群;针对构建的工艺仿真模型,实现流动腐蚀关键参数群的风险预测。结果表明:标况下,空冷器进口Kp<0.5,NH4HS浓度<4%,与美国石油协会932B(API932B)推荐的指标相比,多相流冲蚀风险相对较小。然而,I、II系列空冷器第6管排内管束的流速分别偏低36%和36.5%,存在一定的铵盐结晶腐蚀的风险。基于构建的流动腐蚀风险预测结果,建立了以加氢控制空冷系统管束内Kp、流速、NH4HS浓度等关键流动腐蚀影响参数的控制方法,提出降低注水量、减少管束根数的耐流动腐蚀防控策略;并以提升管束内流速、满足传热要求为目标函数,实现了传热效率校核。该方案在加氢空冷器流动腐蚀防控的基础上,为装置的优化运行和操作提供了重要数据支撑。

Based on correlation analysis of processes,a process model using the reverse sequence backward method was obtained to study the mechanism of ammonium salt crystallization and multiphase flow erosion-corrosion under flow-heat transfer-phase behavior environment in I and II series residual oil hydrotreating air cooler systems.Flow corrosion key parameters of the hydrogenation air cooler system including Kp,velocity and NH4HS concentration were specified.Risk prediction of flow corrosion key parameters was achieved.The results indicate that Kp is less than 0.5 at the air cooler inlet and NH4HS concentration is below 4%.Compared with the recommended index of API 932B,the risk is relatively low.However,the velocity of the tube bundle in the 6th row of the I and II series air coolers was decreased by 36%and 36.5%respectively,and risk of crystallization corrosion of ammonium salt existed.A controlling method was built to adjust key flow corrosion key parameters including Kp,velocity and NH4HS concentration in the bundle of hydrogenation air cooler system,and the flow corrosion and control strategy in reducing water and bundle numbers were proposed.The increase of velocity in tube bundles and heat transfer satisfaction were checked,which provide theoretical support for the optimized operation and control of flow corrosion.