316L复合板减压塔腐蚀穿孔原因分析

对某石化公司Ⅰ套蒸馏装置316L复合板减压塔腐蚀穿孔原因进行了调查分析。结果表明,316L复合板减压塔腐蚀穿孔并非是加工原油性质变化引起,也不是316L不锈钢不能抵抗环烷酸腐蚀,而是由于减压塔制造过程中部分焊缝焊材选择不当,致使焊缝Mo元素偏低,抗环烷酸腐蚀性能下降造成的局部腐蚀穿孔。根据该公司316L复合板使用5 a后塔壁基本没有发生腐蚀,而焊缝由于材质问题发生腐蚀,证明316L是经济可靠的耐环烷酸腐蚀材料。分析了316L抗环烷酸腐蚀的机理,论述了Mo元素的重要作用,提出为了抵抗环烷酸腐蚀必须确保316L材料中Mo质量分数大于2.5%,同时要加强设备监造的质量控制。

Analysis of Corrosion Failure of 316L Composite Plate Vacuum Tower

The corrosion failure of vacuum distillatin tower of 316L composite plate in PetroChina Karamay Petrochemical Company was investigated and analyzed. The results show that the corrosion failure was caused by the local corrosion failure because of inappropriate material selection for the welds in the process of fabrication of vacuum tower, the lower Mo element in corroded welds and reduction of naphthenic acid corrosion resistance performance rather than the variations of crude oil properties and poor performance of 316L stainless steel against naphthenic acid corrosion. There was little corrosion on the 316L wall of Tower 5a. and only a little corrosion was found in the weld because of weld material. All these prove that 316L steel is an economic reliable material resistant to naphthenic acid corrosion. The corrosion resisting mechanisms of 316L steel are studied, and the importance of Mo element is described. It is recommended that the mass percentage of Mo in 316L steel be higher than 2.5% and the manufacturing quality of the equipment be strictly controlled to have a good resistance to naphthenic acid corrosion.