柴油加氢装置高压热交换器腐蚀泄漏原因分析及预防措施

Cause Analysis and Preventions for Corrosion and Leakage of High-pressure Heat Exchanger in Diesel Hydro-treating Unit

针对发生泄漏的兰州石化炼油厂柴油加氢装置高压热交换器E1102,进行了设计、制造及运行工况分析,确定造成换热管腐蚀开裂的主要原因为实际工况偏离设计工况。根据实际工况重新核算了铵盐结晶温度,对比了铵盐结晶温度与管程介质运行温度,确认实际工况的偏离不足以造成氯化铵结晶析出。在考虑换热管内壁存在层流区及结焦等非理想情况后,重新核算了换热管内壁的壁面温度,确认其低于介质温度和铵盐结晶温度,是造成热交换器E1102报废的根本原因。根据原因分析结果,提出了设备和操作两方面的结盐预防措施。

The design,manufacture and operation of the high-pressure heat exchanger E1102 of diesel hydro-treating unit of CNPC Lanzhou Petrochemical Company Refinery has been reviewed for its leakage failure. The main reason of heat exchange pipe corrosion and crack has been verified as a deviation of actual operation conditions from the designed. The ammonium salt crystallization point was recalculated and compared with pipe side medium temperature under actual working conditions,which evidence the deviation is not enough to result in the ammonium salt crystallization. The heat exchanger pipe inner wall temperature was recalculated with additional consideration of non-ideal conditions as the existence of laminar area and coking area,and the calculated temperature is lower than the pipe side medium temperature and the ammonium salt crystallization temperature which was recognized as the root cause for the discarded E1102. Preventions to avoid ammonium salt crystallization were proposed from equipment and operation considerations.