加工海洋高酸原油减压塔腐蚀原因分析

Analysis of Corrosion in Vacuum Distillation Tower for Processing High TAN Crude Oils

某炼油厂常减压装置加工重质高酸低硫原油,通过对该装置进行腐蚀调查发现,减压塔减四线段、减五线段塔壁及内构件腐蚀严重,其中材质为317L不锈钢的填料在使用一年就出现了腐蚀穿孔、机械强度下降现象。对原油性质、设备材质及腐蚀介质流速等方面进行综合分析,结果表明:该装置加工高酸低硫原油的单一性(原油酸值为3.61 mg KOH/g,硫质量分数为0.41%;装置设计原油加工能力为1.5 Mt/a,上一周期加工单一型号海洋高酸低硫原油约1.3 Mt)是引起减压塔高温环烷酸腐蚀的关键原因;装置加工负荷大,加工原油线速度加快,导致减压塔环烷酸腐蚀速度加快;同时,减压油气分配器的不对称安装,导致塔内油气偏流,又加剧了环烷酸对塔内件的腐蚀。针对以上腐蚀原因从设备材质控制和工艺防腐方面提出了相应的防腐建议和措施。

The atmospheric and vacuum distillation unit was operated to process high TAN crudes in a refinery. The corrosion investigation found severe corrosion in the vacuum tower wall of 4th side - draw and 5th side - draw and tower internals. The packings of 317L stainless steel suffered from corrosion rupture after one year＇ s operation, and the mechanical strength went down. The comprehensive analysis of crude oil properties, equipment materials and flow velocity of corrosive medial showed that the processing of only a single high -TAN low sulfur crude （crude＇ s total acid value： 3.61 mgKOH/g, sulfur： 0.41% , unit design capacity： 1.5 MM TPY, 1.3 million tons of ocean high - TAN low sulfur crude oil was processed in the last operation cycle） is the culprit of high - temperature naphthenie acid corrosion of vacuum tower. The high operating capacity and high flow velocity of crude oil feedstock have accelerated the naphthenic acid corrosion of vacuum tower. In addition, the un - symmetry installation of vacuum oil vapor distributor resulted in deflected flow of oil vapor inside the tower which has accelerated the corrosion of tower internals by naphthenic acid. Corresponding corrosion prevention recommendations and measures are presented in respect of control of equipment materials and process corrosion prevention.