Highly concentrated ammonium phosphate/ammonium - nitrate fertilizer - by controlled nitricacid digestion of mineral ph

摘要

Prepn. of fertilisers with a N:P2O5 ratio of approx. 1:1 by (a) treating a mineral phosphate with nitric acid and a source of SO42- ions e.g. ammonium sulphate, and opt. H2SO4, the concn. of HNO3 being kept at 45% of the theoretical amount required for dissolving the chalk present in the mineral, and the source of SO42- ions and opt. H2SO4 combined being sufficient to pt. the chalk present as CaSO4. (b) separating the CaSO4 ppt. concentrating the nitrate and treating it with NH3 at a pressure slightly above atmos. to give a product which is mainly (NH4)2HPO4.