Abstract: The industrial operation effect of pretreatment of gasification wastewater from SE coal slurry by sodium carbonate softening-stripping ammonia removal process in a refinery was analyzed. The results showed that when the wastewater flow rate was 160 m³/h, pH of the wastewater was 10.5-11，the chemicals addition order of sedimentation tank was NaOH, Na₂CO₃, polymeric aluminium chloride (PAC), polyacrylamide (PAM), the steam flow rate of the stripper was 7.5-8.5 t/h, the pressure was 0.14-0.16 MPa, and the temperature at the column kettle was not more than 125 ℃, the discharge concentration of hardness and ammonia-nitrogen of wastewater could be reduced to 174 mg/L and 17 mg/L respectively, and the pollutant indexes were better than the design values.

Key words: gasification wastewater, high ammonia nitrogen, high hardness, sodium carbonate softening, steam stripping deamination, pH