Ammonium phosphate from raw phosphate - by digesting with sulphuric acid and ammonium monosulphate and extracting with hot moth

摘要

Raw phosphate is digested in conventional appts. with sufficient H2SO4 and NH4HSO4 to give calcium sulphate and monoammonium phosphate, the latter being dissolved out with hot mother liquors originating from the process, crystallised out after evaporative cooling, and dried. In an alternative procedure, the hot monoammonium phosphate soln. is adjusted to 57-73% H2O, ammonized, and cooled to 15-20 degrees C., to precipitate mono-, di- or tri-ammonium phosphate, depending on the amount of NH3 used for the ammonization. The use of NH4HSO4 in the digestion reduces the amt. of H2SO4 required and enables the digestion and reaction of resulting H3PO4 to give monoammonium phosphate to be carried out simultaneously, resulting also in savings in NH3 requirements. The ammonium phosphate products are of use in fertilisers.