柴油改质装置热低分空冷器腐蚀失效分析

Analysis on Corrosion Failure of Air Cooler of Hot Low-Pressure Separator for Diesel Upgrading Unit

柴油改质装置热低分空冷器在服役过程中15CrMo螺旋换热管出现明显的泄漏失效现象。通过基材和腐蚀产物成分分析以及CFD仿真模拟分析,探究了该空冷器的腐蚀成因。研究结果表明,该螺旋管腐蚀失效的原因主要是空冷器在服役期间,由于热膨胀导致螺旋管之间直接接触,而发生换热管间的热传导,改变了壁面的温度分布,使得接触处壁面产生局部过冷现象,最终管内高温流体骤冷发生凝结而引起的露点腐蚀失效。基于以上腐蚀成因,提出相关防护建议。

The spiral heat exchange tube made by 15 CrMo stainless steel suffered from obvious leakage failure during service period at the air cooler of hot low-pressure separator for diesel upgrading unit. Corrosion causes of the air cooler were investigated by analyzing the composition of substrate and corrosion products and CFD simulation analysis. Research result showed that the corrosion failure of the spiral tubes was mainly caused by the direct contact between the spiral tubes due to thermal expansion during the service period of the air cooler, and the heat conduction between heat exchange tubes occurred, which changed the temperature distribution of the wall surface, causing local supercooling of the wall surface at the contact point. Finally, the sudden cooling of high-temperature fluid in the tubes caused condensation, causing dew point corrosion failure. Based on the above corrosion cause, corresponding protective recommendations were put forward.