Removal of ammonia from effluent water - by treating in a column with milk of lime, removing ammonia with a hot gas stream and burning the lime sludge

摘要

In parent patent ammonia is expelled from an ammonia-contg. soln., which has been treated with milk of lime in a stripping column and from which the ammonia has been driven out with a hot gas, steam or vapours. A bottom prod. is drawn off contg. lime sludge, calcium sulphate, unused hydroxide, calcium carbonate and other calcium compounds, and passed to a settling unit in which the sludge is separated from the liquid. A pumpable sludge is withdrawn from the settling unit and passed to a combustion chamber together with fuel gas and air, and burnt under reducing conditions at 600-1200 degrees C. The resulting combustion gases are led into an immersion vessel where the resulting calcium compounds are converted into Ca(OH)2 with an aq. liquor, and the resulting vapours are used for other purposes. Pref. in the addition, combustion is at 600-900 degrees C giving Ca sulphide which reacts with the aq. liquor to give calcium hydroxide and calcium hydrosulphide.