加氢精制U形管式换热器管束泄漏分析与对策

Leak Analysis and Countermeasures of the U-tube Exchanger Bundle in the Hydro-refining Unit

炼化加氩装置采用的Q环焊接密封U形管式换热器,解决了管箱法兰与壳体法兰夹持管板的密封外漏问题,但却发生管束的内漏。对某加氢精制装置用U形管式换热器管束内漏进行讨论,从工况的腐蚀性、设计的合理性、材料的耐蚀性等方面进行了分析,发现其中一台321管束换热器由于设计时没有考虑铵盐结晶及注水溶解,引起了使用中管束U形管铵盐结晶发生垢下腐蚀泄漏;另一台15CrMo换热器管束则因硫腐蚀泄漏较前两台提前更换管束。建议在完善工艺与检修过程防腐控制的同时,15CrMo管束改用321材料。

The leakage of the sealing surfaces between the channel flange/shell flange and the tubesheet has been solved, when the U-tube exchanger with Ω welding sealing ring used in the hydro-refining unit. But the internal leakage occurred in the tube bundle. The internal leakage of the U-tube exchanger bundle in the hydro-refining unit was discussed in term of the corrosiveness of the working conditions, the rationality of the design and the corrosion resistance of the material. As there is no consideration of water injection for ammonium salt crystallization, the U-tube leakage is caused by the under-deposit corrosion due to the ammonium salt crystallization in the tube bundle made of 321 stainless steel.Because of the sulfur corrosion leakage, the tube bundle made of 15 CrMo has been replaced in advance. It is recommended to improving anticorrosion in the operation process and the maintenance process, the 15 CrMo steel used in the tube bundle should also be replaced by 321 steel.