Causes of corrosion in the overhead condensation system of petrochemical refineries

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Corrosion in the low-temperature areas of crude oil distillation units mainly occurs in the condensation systems at the tops of the three towers, namely the tower tops, vaporization lines for oil and gas, air coolers, water coolers, and reflux tanks; it is a form of corrosion caused by the HCI-H2S-H2O mixture. Thinning and cracking of the cold exchange shell, cracking of 18-8 material tube bundles, thinning and perforation of the vaporization lines, and numerous perforations in the air coolers all fall under this type of corrosion. Corrosive medium: Although the crude oil processed by distillation units undergoes deep desalination, which allows for the removal of most inorganic salts (such as MgCl2 and CaCl2), the unstable quality of electrodesalination results in a large amount of HCl being generated as a result of the hydrolysis of inorganic salts present in the crude oil; this HCl then enters the condensation system as a corrosive agent. The corrosive agent H2S originates mainly from the sulfides in crude oil; during processing, these sulfides are heated and decomposed, producing large amounts of H2S, which then enters the top section of the tower along with the oil and gas. Since HCl and H2S enter the three-top condensation system along with the oil and gas, corrosion in the HCl-H2S-H2O system occurs.