Abstract: A refinery processes Tarim-Tuha-Yumen mixed crude oil, which has shown a clear trend of becoming heavier and inferior in recent years. The refinery analyzed the problems of reduced desalting efficiency and deterioration of wastewater after desalting encountered in crude oil pretreatment, and implemented measures such as addition of sewage deoiling device, intelligent response AC and DC desalting technology, sewage tank sedimentation, and three-phase separation treatment of wastewater after desalting in steps. By using the technical transformation, the operating conditions and sewage properties of the electric desalination system have been significantly improved. After the electric desalination, the content of salt in the oil is less than the limit of 2 mg/L, the oil content of the discharged sewage has been reduced from 1521 mg/L to less than 10 mg/L, and the suspended matter in the discharged sewage has been reduced from 169 mg/Lto 41 mg/L.

Key words: Tarim-Tuha-Yumen mixed crude oil, electric desalination, dehydration, oil removal, three-phase separation