Typical Corrosion Cases and Protective Measures of 12 Mt/a Atmospheric and Vacuum Distillation Unit

Since the start-up of a 12 Mt/a atmospheric and vacuum unit, low temperature corrosion at atmospheric overhead, reduced corrosion of the third-line tower wall and fuel tank, and stable roof-top air-cooling corrosion occurred. The causes of corrosion were analyzed and protective measures were proposed. Low temperature corrosion at the top of the tower was mainly due to hydrochloric acid corrosion and NH₄Cl under scale corrosion. The corresponding measures were as follows:2-3 mg/L NaOH was added to the crude oil after electric desalting; the water injection port of the top volatilization line was changed to water inlet at the air cooler; the protective measures such as device material upgrading, raw material control, operation adjustment and corrosion monitoring were carried out in a targeted manner. The corrosion of the third line and the fuel tank was typical high-temperature sulfur and naphthenic acid corrosion. It was necessary to use material upgrade, control of raw material sulfur content and acid content and other corrosion protection measures. The air-cooling corrosion leakage at the top of the stable tower was caused by the welding process and quality problems of 2205 duplex steel. It was necessary to control the quality of the equipment and the sulfur and chlorine content in the raw oil. The operation of the device showed that protective measures were proper and the corrosion risk was basically controllable.