Manufacture of solid ammonium phosphate

摘要

The invention relates to a process for the manufacture of solid monammonium phosphate in a suitable form for use as an ingredient in the granulation of NPK compound fertilizers. It has been found that some wet-process phosphoric acids used in the manufacture of fertilizer grade ammonium phosphate contain impurities in amounts and/or ratios which can give rise to hard oversize product in known methods of manufacture with the result that extra milling of the product is required. The process of the invention overcomes the need for extra milling by providing an improved product form. The improvement is achieved by mixing separately at one stage in a process of the kind described between 15% and 85% by volume of the total secondary acid feed with the aqueous ammonium phosphate slurry and adding the remainder of the secondary acid to the treated slurry at a later stage.