延迟焦化装置的典型腐蚀与防护

TYPICAL CORROSION CASES AND PROTECTIVE MEASURES OF DELAYED COKER

针对自2016年大检修以来,中国石化北京燕山分公司延迟焦化装置出现的原料缓冲罐罐顶平衡线腐蚀、焦炭塔上进料线弯头腐蚀、解吸塔塔底重沸器壳体腐蚀、稳定塔塔顶冷却器管束腐蚀等进行腐蚀原因分析,并提出了相应的防护措施建议。原料缓冲罐罐顶平衡线腐蚀为高温硫腐蚀,需要采用对管线材质升级或加防腐蚀内衬等措施;焦炭塔上进料线弯头腐蚀为湿硫化氢腐蚀和冲刷腐蚀共同作用,应该在塔顶处采取阀门隔断;解吸塔塔底重沸器壳体腐蚀为壳体下部两侧区域形成滞留区和腐蚀介质浓缩引起的低温硫腐蚀,需要控制原料的硫含量并将重沸器材质进行升级;稳定塔塔顶冷却器管束腐蚀以溶解氧腐蚀为主、垢下腐蚀为辅,管束内壁结垢并发生金属腐蚀,应做好在线监测、适当提高水冷却器管程流速等。装置运行情况表明,采取适当的防护措施,装置腐蚀风险基本可控。

Since the overhaul of the delayed coking unit in 2016,there have been corrosion on the top of the raw material buffer tank,the feed line on the coke tower,the shell of the reboiler at the bottom of the tower,and the cooler bundle at the top of the tower.The causes of corrosion were analyzed and protective measures were proposed.The short joint corrosion on the top of the raw material buffer tank is high temperature sulfur corrosion,which needs to adopt measures such as material upgrading or pipeline lining.The corrosion of the elbows of the feed line on the coke tower is due to the joint action of low temperature sulfur corrosion and erosion corrosion.The valve should be cut off or added heat tracing at the top of the tower.The corrosion of the reboiler shell at the bottom of the analytical tower is the electrochemical corrosion.It is necessary to control the sulfur content of the raw materials and to upgrade the reboiler equipment.The corrosion of the cooler tube bundles on the top of the stability tower is the inner wall scaling and metal corrosion of the tube bundles.The operation of the device showed that protective measures were proper and the corrosion risk was basically controllable.