Process for producing granular diammonium phosphate

Abstract

A process is disclosed for the manufacture of granular diammonium phosphate (DAP) by reacting anhydrous ammonia with phosphoric acid in a reactor to form reaction product consisting of a partially reacted slurry of monoammonium phosphate and diammonium phosphate. The slurry is pumped to a rotary granulator-reactor where it is further reacted with anhydrous ammonia to form a solid granular diammonium phosphate mixture having a range of particle sizes consisting of undersize, oversize and product. After drying the diammonium phosphate mixture, a portion of the dried granular diammonium phosphate mixture is diverted back to the granulator-reactor prior to delivery to a classifying means. The portion of dried granular diammonium phosphate mixture not diverted to the granulator-reactor, is introduced to a classifying means set to a narrow separation to separate undersize and oversize granular particles from the desired product granular particles. The oversize granular particles are milled and recycled to the granulator-reactor along with the undersize granular particles obtained during the classifying process. The desired granular particles which have a size in the range of 2 mm to 4 mm are collected. About 90% of the granules collected by the classifying means as product are in a range of the desired granule size of 2 mm to 4 mm.