Ammonium sulphate contg. waste water treatment - by concn., crystalline ammonium sulphate sepn., mother liquor crystallisation and ammonia treatment

摘要

(NH4)2SO4-contg. waste waters contaminated with organic cpds. and opt. NH4NO3 are worked up by concn. opt. in several steps, with sepn. of crystalline (NH4)2SO4. The residual mother liquor discharged from the last evapn. step is opt. subjected to vacuum cooling crystn. at 10-80 (esp. 40-55) degrees C. The (NH4)2SO4 formed is separated and pref. recycled to evapn.-crystn. the conc. (NH4)2SO4- contg. mother liquor is diluted with water. The soln. is then mixed with NH3 at pressure 5 kg./cm2. Crystallising (NH4)2SO4 is separated from the ammoniacal mother liquor, opt. washed free from NH3 and recycled, esp. to evapn.-crystn. NH3 is recovered by disn. from the ammoniacal mother liquor. The process can be used in working up effluents from epsilon -caprolactam or acrylate prodn. Coarse-grained, easily scattered, colourless pure (NH4)2SO4, for use as fertiliser, can be recoved in up to 99.8% yield.