常减压蒸馏装置常顶换热器腐蚀分析

某公司10 Mt/a常减压装置检修时发现常顶双相不锈钢换热器管板表面腐蚀,出现微裂纹。对常顶换热器管板及管束进行成分检测及管束涡流检测,结果显示材质符合设计要求,未发现管束内部明显腐蚀减薄。同时对现场采用的工艺防腐措施、现场监测情况进行了调查分析,并在实验室内开展了模拟评定试验。分析认为,常顶注水量低于国内同行业该部位注水量,注水水质为脱硫净化水及部分塔顶冷凝水,还添加了不同性质的注剂,增加了塔顶腐蚀环境的复杂性,容易在应力集中部位形成表面微裂纹。建议增大常顶系统注水量,改善注水水质,并严格控制各种离子含量,同时进一步优化工艺防腐措施。

Corrosion analysis of atmospheric tower overhead heat exchanger in atmospheric- vacuum distillation unit

Surface corrosion and micro cracks were found on tube sheets of duplex steel overhead heat exchanger of atmospheric tower. The chemical components of the tube sheet and tube bundles were tested to confirm whether the materials meet the design requirements. Eddy current testing for tube bundles was conducted. The test results confirmed that the material meets the design requirement. No corrosion and obvious thickness reduction were found inside the tubes. Protective measures and field corrosion monitoring were investigated and analyzed. The simulation experiments were conducted in the laboratory. The results of analysis show that, although water injeetioll measures were taken, the overhead water injection rate of atmospheric tower was lower than that in other domestic refineries, the injection water was desulphurization purified water and overhead condensate water anddifferent additives were injected at the top of atmospheric column. All these have increased the complexity of the overhead corrosion environment, and micro -cracks were formed on the surface area with stress concentration. It is suggested that water injection rate should be increased at the overhead of the atmospheric tower and injection water quality should be improved to strictly control the various ion contents. At the same time, the effective anti - corrosion measures should beselected.