Uniform corrosion caused by low-temperature sulfur corrosion

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It is mainly a corrosion environment of the HCI+H2S+H2O type; such an environment is found primarily in distillation column tops and in areas where the temperature is below 150°C. The areas where phase change occurs, that is, the dew point areas, are the most severely affected. Organochlorines and a small amount of unremoved inorganic salts decompose within the tower as the temperature of the oil rises, generating large amounts of HCl. Meanwhile, the reactive sulfur compounds in the oil produce H2S within the tower. In the areas with localized high temperatures at the top of the tower, as well as in the gas-liquid phase transition zone where the temperature is ≤120°C, H2S and HCl dissolve together in the condensate water, creating a corrosive environment of low-temperature HCl-H2S-H2O at the tower top. HCl and H2S reinforce each other, leading to cyclic corrosion that results in severe corrosion in the low-temperature areas of the tower. The corrosion reactions are as follows: Fe + 2HCl → FeCl2 + H2; FeCl2 + H2S → FeS + HCl; Fe + H2S → FeS + H2; FeS + 2HCl → FeCl2 + H2S