炼油厂设备腐蚀故障失效分析三例

Study on Three Cases of Corrosion Failures of Refinery Equipment

结合炼油厂常减压蒸馏装置顶循环油/原油换热器管束泄漏;硫酸烷基化单元反应流出物碱洗罐入口混合器前管段穿孔和汽柴油加氢精制单元柴油蒸汽发生器泄漏等三例设备腐蚀案例进行了失效原因分析。分析结果表明:常减压蒸馏装置顶循环油/原油换热器管束泄漏由管程介质即顶循环引起,为HCl结露产生的H2O-HCl体系腐蚀所致;硫酸烷基化单元反应流出物碱洗罐入口混合器前管段穿孔由于注碱方式导致反应流出物和热碱水在混合过程中产生局部低压区,造成C4蒸发,大大加快了流速。另外碱液中水分稀释反应流出物中夹带的浓硫酸,使其含量变低,从而导致20合金的严重腐蚀;汽柴油加氢精制单元柴油蒸汽发生器泄漏主要由于壳程介质水、蒸汽或换热管与管板的联接制造缺陷引起。最后针对不同的腐蚀问题提出了防护措施。

In the study of 3 corrosion failure cases of refinery equipment, i.e. corrosion leakage of recycle oil/crude oil heat exchanger in atmospheric - vacuum distillation unit overhead, failure of pipeline upstream of inlet mixer of caustic wash drum of reactor effluent of sulfuric acid alkylation unit and corrosion leakage of steam generator in gasoline and diesel hydrotreating unit, the causes of corrosion failures of refinery equipment were analyzed. The results demonstrated that, the corrosion leakage of atmospheric -vacuum distillation unit overhead recycle oil/crude oil heat exchanger was caused by tube side media （overhead recycle oil） ; The corrosion was the result of H20 - HC1 system produced by HC1 dew formation. The pipeline upstream of inlet mixer of caustic wash drum of reactor effluent of sulfuric acid alkylation unit failed because of accelerated flow velocity caused by Ca vaporization in the low - pressure zone in the mixing of reactor effluent and hot caustic water due to the inappropriate ways of caustic addition. In addition, the water in caustic liquid diluted the sulfuric acid carried over with the reactor effluent, leading to serious corrosion of 20 alloy steel. The leakage of steam generator in gasoline and diesel hydrotreating unit was mainly caused by shell side media, water or fabrication defects of connection of heat exchanger tubes and shell plates. Prevention measures are recommended based upon different corrosion conditions.