N-P grades, are the reaction products of varying degrees of neutralization of phosphoric acid with anhydrous ammonia. The different products taht are marketed worldwide vary widely in nitrogen and P 2 O 5 guarantees and are produced by various processes and modifications. Although manufacturing processes and techniques differ among the various are plants, the first step in ammonium phosphate production is the partial neutralization of the the phosphoric acid with anhydrous ammonia in a reaction vessel.
Water vapor is evolved from the heat of reaction of the acid and ammonia.
The partially neutralized slurry is then pumped to an ammoniator granulator where it is distributed over the rolling bed of recycled fines from the product screening operations and sufficient anhydrous ammonia is added to produce the desired product grade. The product from the granulator discharge into a rotary dryer where the moisture content is reduced to the desired level. The dryer discharge is then fed to the screening section to separate the product size from the undersize and oversize materials. The oversize, after being crushed, is either rescreened or recycled together with the undersize fractions back to the ammoniator granulator. The on-size products from the screening operation is passed through a rotary cooler and then conveyed to storage.