Improvements in or relating to the production of granular fertilisers comprising monoammonium phosphate

A granular fertilizer comprising mono-ammonium phosphate is produced by mixing ammonia and an aqueous medium containing phosphoric acid with a workable aqueous slurry containing ammonium phosphate of N : P atomic ratio between 1.10 and 1.45 in proportions to give more of said aqueous slurry at an N : P atomic ratio between 1.10 and 1.45 and then mixing with the slurry produced an acidic material, e.g. HNO3, H2SO4 or H3PO4 to reduce the N : P atomic ratio to about unity and solid materials under conditions to produce incipient granulation and drying the granules so formed. The phosphoric acid in said aqueous medium contains a percentage by weight of P2O5 greater than the maximum to yield a workable slurry when treated with ammonia to give an N : P atomic ratio of 1.0 but not more than 5% by wt. of P2O5 in excess of such maximum. The aqueous medium containing phosphoric acid may be treated with ammonia to an N : P atomic ratio less than 0.9 prior to admixing with the workable aqueous slurry and further ammonia. By utilizing an acid other than phosphoric in the last stage of the process, i.e. to reduce the N : P ratio to about unity, mixed fertilizers may be produced. The solid materials used to produce granulation are preferably recycled product.