酸性水汽提装置工艺防腐研究

Study on Process Corrosion Prevention of Sour Water Stripping Unit

某炼油厂酸性水汽提装置采用双塔加压汽提工艺,运行过程中空冷管束、换热器芯子、工艺管道等部位多次发生腐蚀,调查发现主要原因为气相铵盐结晶造成的冲刷腐蚀和高浓度硫氢化铵液体化学腐蚀。通过运用PROII工艺模拟软件对酸性水汽提装置进行全装置模拟,一方面得到装置内气相组分的Kp值数据,通过查表,获得气相组分的硫氢化铵结晶温度,为日常控制确保不发生铵盐结晶提供理论依据。另一方面得到液相部分的硫氢化铵水溶液浓度和管线介质流速,对照文献获得相应的腐蚀速率,为日常监控装置腐蚀提供数据支持。根据实际经验和模拟结果,一级气氨冷却器温度适宜控制在95~100℃,二级气氨冷却器温度适宜控制在40~45℃,三级气氨冷却器温度适宜控制在23~25℃。硫氢化铵水溶液质量分数适宜控制在8%以下,管线流速控制在2m/s以下。同时要严格控制脱硫化氢塔底污水硫化氢含量,控制硫化氢脱除率在95%以上,减少后续流程介质硫化氢含量,降低腐蚀。

Double tower pressurized stripping process was used in the sour water stripping unit of a refinery.During operation,the air cooler tube bundle,the heat exchanger core,the process pipelines and other parts have been corroded for many times.It was found that the main causes were the erosion corrosion caused by the crystallization of gas phase ammonium salt and the chemical corrosion caused by high concentration ammonium hydrogen sulfide liquid.The whole sour water stripping unit was simulated by using PROII process simulation software.On the one hand,the Kp value of gas phase components in the unit was obtained.By looking up tables,the crystallization temperature of ammonium hydrogen sulfide of gas phase components was obtained,providing a theoretical basis for the daily control to ensure that no ammonium salt crystallization occurs.On the other hand,the concentration of ammonium hydrogen sulfide aqueous solution in liquid phase and the flow rate of pipeline medium were obtained.By comparing with literatures,the corresponding corrosion rate was obtained,providing data support for the daily monitoring of unit corrosion.According to the actual experience and simulation results,the temperature of primary gas ammonia cooler should be controlled between 95~100℃,the temperature of secondary gas ammonia cooler should be controlled between 40~45℃,and the temperature of tertiary gas ammonia cooler should be controlled between 23~25℃.The mass fraction of ammonium hydrogen sulfide aqueous solution should be controlled below 8%and the flow rate in pipelines should be controlled below 2m/s.At the same time,the hydrogen sulfide content of the bottom sewage of hydrogen sulfide removal tower should be strictly controlled,and the hydrogen sulfide removal rate should be controlled above 95%,so as to reduce the hydrogen sulfide content of the medium in follow-up processes and to reduce corrosion.