Method for treating coal gasification wastewater by single tower alkali injection and pressurization steam stripping

The invention discloses a method for treating coal gasification wastewater by single tower alkali injection and pressurization steam stripping, comprising the following steps: the cold and hot coal gasification wastewater respectively enters a single tower from the upper part and middle upper part of a wastewater steam stripping tower, gas ammonia is extracted from the lateral line of the single tower which goes through three-level dephlegmation to obtain high-concentration ammonia, condensate returns to a stock tank; alkali is injected at the position below the lateral line to transform fixed ammonia into ammonia which is to be removed; the mass percentage concentration of alkali liquor is 20-40%, the use level of the alkali liquor is not more than that of mol number of fixed ammonia in the wastewater, and residue is extracted from the tower bottom and is subjected to follow-up extraction and dephenolizing process of coal gasification wastewater. In the method of the invention, the process removing acid gas, free ammonia and fixed ammonia is carried out simultaneously on the coal gasification wastewater in the wastewater steam stripping single tower, as a result, high-concentration ammonia is obtained, the content of carbon dioxide, sulfureted hydrogen, free ammonia and fixed ammonia in tower kettle purified water is extremely low, encrustment is not prone to take place, pH value is reduced to around 6, as a result, fine extraction conditions are created for the follow-up solvent extraction dephenolizing of the coal gasification wastewater. The method of the invention is suitable for the coal gasification wastewater and overall treatment process thereof.