METHOD OF PREPARING DIAMMONIUM PHOSPHATE Russian patent published in 1998 - IPC

FIELD: mineral fertilizer for various types of soils. SUBSTANCE: method comprises stage-by-stage neutralization of ammonia with acid compound containing phosphoric acid to molar ratio of NH₃: H₃PO₄=1.4 and then to 1.75, granulation, drying, classification of the final product and subsequent purification of off-gases. Prior to neutralization, sulfuric acid is added to phosphoric acid till SO₃: P₂O₅ ratio of 1: 9-15 is attained. Purification of off-gases is carried out in two stages. The first stage uses pulp of ammonium phosphates at NH₃: H₃PO₄ molar ratio of 0.4-0.6, and purification is carried out till 30-50 % ammonia of the total amount are absorbed in gases admitted for purification purposes, and the second stage uses extraction phosphoric acid, and purification is carried out till sanitary norm of ammonia is attained in exhaust gases. The present invention makes it possible to increase yield of commercial granular product of narrower (2-4 mm) fraction to 85-90 %, decrease power consumption and reduce ammonia content in exhaust gases. EFFECT: more efficient preparation method.