Ammonia removed from aq. effluents by stripping with air - with subsequent absorption of ammonia in acid soln and recirculation of air

摘要

Ammonia is removed from aq. effluents by stripping with air, then ammonia is removed from the sir stream by absorption in an acid soln. (pref. pH 6.5) contg. H2SO4 or HCl; the air is recycled; (NH4)2SO4 or NH4Cl are recovered. The aq. effluent is preliminarily treated with an alkali to adjust the pH to a value above (pref. 11). The air-bubbling is carried out at 5-25 degrees C. The process is carried out at normal temps. The air cycle is closed, whereby CO2 is not supplemental and precipitation of CaCO3 from the alkali-treated effluents is avoided. NH4Cl and (NH4)2SO4 can be recovered and utilised (the latter as a fertiliser).