12Mt/a常减压装置的典型腐蚀及防护

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

某12Mt/a常减压装置自开工以来出现了常压塔顶低温腐蚀、减三线塔壁及集油箱腐蚀、稳定塔顶板式空冷腐蚀等,对腐蚀原因进行了分析,并提出了防护措施。塔顶低温腐蚀主要是由于盐酸和NH4Cl垢下腐蚀,应采取在脱后原油中加注2~3mg/L NaOH,将塔顶挥发线注水口改在空冷器入口分别注水,进行装置材料升级、原料控制、操作调整、腐蚀监测等防护措施。减三线及集油箱腐蚀是典型的高温硫和环烷酸腐蚀,需要采用材质升级或控制原料硫含量、酸含量等腐蚀防护措施。稳定塔顶空冷腐蚀泄漏则是由2205双相钢焊接工艺及质量问题造成的,需要控制设备制造质量及原油中的硫、氯含量。装置运行情况表明,采取的防护措施得当,腐蚀风险基本可控。

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 NH4 Cl 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.