METHOD OF PREPARING DIAMMONIUM PHOSPHATE Russian patent published in 2000 - IPC

FIELD: preparation of diammonium phosphate for various types of soils. SUBSTANCE: method comprises stage by stage neutralization of mixture of sulfuric and phosphoric acids to molar ratio of NH₃:H₃PO₄= 1,4 and then to 1.75, granulation, drying the product and subsequently purifying the off-gases in two stages, first with pulp of ammonium phosphates and then with phosphoric acid. Phosphoric acid fed to neutralization is mixture of evaporated and unevaporated acids which are premixed in amounts required to attain F:P₂O₅ of 0.03-0.05 and concentration of 40-46%. EFFECT: plastic surface of the resulting granules the strength of which does not exceed 30-40 kgf/sq.cm