Heavy oil sewage treatment system

The utility model relates to the technical field of wastewater energy-saving and environment-friendly treatment, in particular to a thickened oil sewage treatment system which comprises an oil extraction device, an oil-water separation device, a deep pretreatment device, a multi-effect evaporation and MVR evaporation device and a salt drying device which are connected in sequence. Oil is separatedfrom an oil-water mixture extracted by the oil extraction device through an oil-water device, heavy oil sewage is subjected to deep pretreatment, impurities are removed, and oil in the sewage is further recycled; the light-phase sewage subjected to deep pretreatment enters a multi-effect evaporation and MVR evaporation device to be evaporated and concentrated, enthalpy of secondary steam generated by evaporation is increased through a steam compressor to serve as a heat source for system evaporation to be recycled, energy is saved by 80% or above, and water is saved by 90% or above; and the dried wet salt meets the i