哈氏合金C-276管束在PTA装置尾气中腐蚀的关键因素分析

ON KEY FACTORS OF CORROSION OF HASTELLOY C-276 TUBE BUNDLE IN PTA PLANT TAIL GAS

某石化PTA装置尾气催化燃烧第一预热器哈氏合金C-276管束在运行13年后出现管束进口100~300 mm范围腐蚀问题,在更换同材质换热器管束后,仅运行三个半月又发生同样的腐蚀现象。针对上述问题,通过对比运行时间、操作条件、介质成分变化等因素,结合换热管腐蚀形貌、腐蚀产物能谱分析,以及换热管内流动进口区速度边界层分析结果,研究了C-276管束在进口端发生的高腐蚀速率行为,确定了腐蚀机理,得出尾气中水分的增加是导致腐蚀失效的关键因素的结论,同时,根据分析结果提出了相应的防护建议。

Corrosion of Hastelloy C-276 tube bundle of the first preheater for tail gas catalytic combustion in a petrochemical PTA plant occurred in the range of 100 to 300 mm at the tube bundle inlet after 13 years of operation.And the same corrosion phenomenon occurred again after only three and a half months of operation after replacing the tube bundle of the heat exchanger of the same material.Aiming at the above problems,the behavior of high corrosion rate of C-276 tube bundles at inlet end was studied by comparing such factors as operation time,operating conditions and changes in medium composition combining with the analysis of corrosion morphology of heat exchanger tubes,energy spectrum analysis of corrosion products and the results of velocity boundary layer analysis in the flow inlet area of heat exchanger tubes,the corrosion mechanism was determined and it was concluded that the increase of water content in the tail gas was the key factor to corrosion failure.Meanwhile,the corresponding protection suggestions were proposed according to the analysis results.