Abstract:

During the regular inspection of a 0.2 MM TPY lubricating oil hydrogenation unit in a petrochemical company, it was found that there was severe corrosion on the tube pass of the high-pressure hydrogenation heat exchanger, mainly concentrated in the lower temperature area of the lower half of the heat exchange tube. According to the analysis of corrosion products, it was mainly underdeposit corrosion caused by ammonium chloride crystallization. The analysis of the operation status of the unit showed that the main factors affecting the crystallization of ammonium chloride included the chlorine content in the feedstock, the water injection effect of the heat exchanger and the operating temperature of the heat exchanger. In the anti-corrosion upgrade and renovation of the heat exchanger, the use of specialized dechlorinating agents effectively reduced the chlorine content of the feedstock, increased the outlet temperature of the tube pass, reduced the possibility of ammonium chloride crystallization, improved the water injection flushing effect, reduced the concentration of ammonium chloride and its residence time on the heat exchange surface. The material upgrade and renovation improved the corrosion resistance of the heat exchange surface metal. During the three-year operation period after the upgrade and renovation, there was no ammonium salt crystallization on the tube pass of the heat exchanger, which prevented the underdeposit corrosion caused by ammonium salt and ensured the long-term operation of the lubricating oil hydrogenation unit.

Key words: lubricating oil hydrogenation, high pressure heat exchanger, ammonium salt crystallization, corrosion under scale, chlorine content

摘要：

某石化公司0.2 Mt/a润滑油加氢装置定期检查中，发现加氢高压换热器管程存在严重腐蚀现象，主要集中在换热管下半部温度较低区域，经腐蚀产物分析，主要是NH₄Cl结晶垢下腐蚀。对装置运行状况分析表明，影响NH₄Cl结晶因素主要有原料油中氯含量、换热器注水效果、换热器操作温度等。在换热器防腐升级改造中，采用专用脱氯剂，有效降低了原料油的氯含量，提高管程出口温度降低了NH₄Cl结晶的可能性，改善注水冲洗效果降低了NH₄Cl浓度及在换热面停留时间，材质升级改造提高了换热面金属抗腐蚀能力。升级改造后的3 a运行期间，换热器管程侧未出现铵盐结晶，防止了铵盐垢下腐蚀的发生，保证了润滑油加氢装置的正常运行。

关键词: 润滑油加氢, 高压换热器, 铵盐结晶, 垢下腐蚀, 氯含量