乙苯装置腐蚀分析

CORROSION FORM ANALYSIS OF ETHYLBENZENE PLANT

某公司乙苯装置经过两个运行周期及两次大检修,发现装置腐蚀主要存在4种形态,主要有湿硫化氢腐蚀、中压蒸汽凝液冲刷腐蚀、弱酸腐蚀及加热炉空气预热器低温露点腐蚀。对此4种较为典型的腐蚀存在部位及成因作简要概括与分析:湿硫化氢腐蚀主要存在于脱丙烯系统,与催化裂化干气中的硫化氢含量有关;中压蒸汽凝液冲刷腐蚀主要存在于管线弯头部位,与选材及工艺控制有关;弱酸腐蚀主要存在于脱非芳塔塔顶冷却系统,与设备材质及塔顶气CO2含量有关;加热炉空气预热器低温露点腐蚀存在于热管预热器的烟气出口,与工艺操作管理有关。由此在加强重点部位监测、合理选材、优化工艺操作等方面提出防护对策。装置经过两个运行周期后,对于易腐蚀减薄的部位已有基础数据积累,同时也应及时关注同类装置的运行情况,保证装置长周期稳定运行。

After two operation cycles and two major overhauls of ethylbenzene unit in a company,four corrosion forms were found:wet hydrogen sulfide corrosion,erosion corrosion by medium pressure steam condensate,weak acid corrosion,and low temperature dew point corrosion of air preheater of heating furnace.The causes for these corrosions were analyzed.It was concluded that the wet hydrogen sulfide corrosion,mainly existed in depropene system,was related to the content of hydrogen sulfide in catalytic dry gas;the erosion corrosion of medium pressure steam condensate mainly occurred at the elbow of pipeline,was related to material and process control;the weak acid corrosion in the cooling system on the top of non-aromatic tower,was related to device material and CO 2 content of tower top gas;while the low temperature dew point corrosion in flue gas outlet of heat pipe pre-heater was related to process operation.Therefore,it is necessary to strengthen the monitoring of key parts,select material reasonably,and optimize operation conditions.After two operation cycles of the unit,the basic data has been accumulated for the parts prone to corrosion and thinning.Meanwhile,timely attention should be paid to the operation of similar units to ensure the stable long term operation.