Abstract: The high-salt wastewater produced by the concentration unit of the reuse water unit of a coal chemical enterprise in China Coal Inner Mongolia Mengda New Energy Chemical Co. , Ltd has the characteristics of large COD change, high hardness, high total silicon and high salinity. It is discharged to the evaporation pond for drying. After technical transformation, the process combination is adopted as high-density tank + multi-media filter + ultrafiltration + ion exchange resin + reverse osmosis + silicon removal sedimentation tank + purification + nanofiltration + advanced oxidation (AOP) + multi-effect evaporation crystallization. The waste water recovery rate is 98%, which is used in circulating water station. The by-products of sodium chloride and sodium sulfate meet the Grade I standard of industrial dry salt of "Sodium Chloride for Coal Chemical By-product Industry" (T/CCT 002-2019) and the grade A standard of "Sodium Sulfate for Coal Chemical By-product Industry" (T/CCT 001-2019) respectively. The mixed salt rate is about 11.8%, and they are disposed of according to hazardous waste. It realizes the resource utilization of waste water and salt. This paper introduces the process selection, engineering design, project investment estimate and operation effect analysis of the project．

Key words: coal chemical industry, high salt wastewater, nanofiltration, evaporation crystallization