1.8Mt/a蜡油加氢脱硫装置高压空冷器腐蚀分析和控制

Analysis and control of HP air cooler corrosion in a 36.000 b/d TPY gas oil hydrodesulfurization unit

介绍中国石化镇海炼化分公司1.8 Mt/a蜡油加氢脱硫装置高压空冷器的腐蚀情况,判断该空冷器存在典型的NH_4 HS,NH_4 Cl垢下腐蚀,在出口底板处还形成了高速冲刷腐蚀。对腐蚀原因进行了详细的分析,结果表明,该空冷器设计的入口流速偏高、出口管线和空冷器变频器的非对称布置导致介质偏流、实际工况下装置加工原料的硫、氮含量峰值远远高于设计值,实际的K_p值大于0.5,注水量偏少,脱硫净化水回用带入氯离子,从而导致铵盐部分结晶形成垢下腐蚀。管箱隔板的平衡孔结构加剧冲刷腐蚀,导致管箱底板穿孔。阐述了装置所采取的系统性的控制措施,并对其效果进行了考察,提出了进一步的强化和改进措施。

The HP air cooler corrosion in a 36. 000 b/d TPY gas oil hydrodesulfurization unit in SINOPEC Zhenhai Refining ＆ Chemical Co. , Ltd was discussed in detail. Typical NH4HS, NH4Cl underdeposit corrosion occurred in the air cooler, and high-velocity erosion was found on the outlet tube bottom. The detailed analysis of corrosion causes concluded that the culprits of the corrosion and erosion were the high design inlet velocity, deflected flow due to unsymmetrical design of outlet piping and cooler frequency converter, higher sulfur and nitrogen in the feed （Kp is greater than 0.5） , carry-over of chlorine ions with returned purified sour water, which lead to the crystallization of ammonia salts and under-deposit corrosion. At the same time, the balancing holes in the shell baffle have aggravated the erosion corrosion, resulting in the failure of shell bottom plate. The systematic corrosion control measures adopted were described and the corrosion control results were studied. Further improvement measures were presented.