Removal of ammonia from effluent waters, e.g. from coking plant - by treating in a column with milk of lime, removing ammonia with a hot gas stream and burning the lime sludge

摘要

Process for expelling ammonia from an ammonia-contg. soln. which has been treated with milk of lime in an expulsion column and from which the ammonia has been driven out with a hot gas, steam or vapours, comprises drawing off a bottom prod. contg. lime sludge, calcium sulphate, unused hydroxide, calcium carbonate and other calcium compounds and passing this 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 A pumpable sludge is withdrawn from the settling unit and passed to a combustion chamber together with fuel gas and air, and burnt under reducing conditions at 600-1200 degrees C, esp. 800-1000 degrees C. The resulting combustion gases are led into an immersion vessel where the resulting CaO is converted into Ca(OH)2 with an aq. liquor, and the resulting vapours are used for other purposes. Process is esp. useful for treating effluent waters from coke works, and gives excellent removal of free and bound ammonia.