GB1135778A - Granular phosphates - Google Patents

Abstract

1,135,778. Granular magnesium ammonium phosphate. SCOTTISH AGRICULTURAL INDUSTRIES Ltd. 21 Nov., 1966 [3 Dec., 1965], No. 51433/65. Heading C1A Granular fertilizer compositions comprising magnesium ammonium phosphate are prepared by reacting and simultaneously granulating by a wet granulation technique a mixture comprising NH 4 H 2 PO 4 and at least one of the compounds MgO, Mg(OH) 2 and MgCO 3 . The term "granular" denotes a particle size range of <SP>5</SP>/ 16 inch-100 mesh B.S. sieve. By "wet granulation technique" is meant agitation of the mixture in a granulating device (e.g. a rotating drum, a pan granulator or a pin mixer) in the presence of sufficient water to effect granulation. Calcined magnesite (MgO) is the preferred magnesium component. When two or three of the aforementioned magnesium compounds are employed, they may be in chemical combination, as in 3MgCO 3 .Mg(OH) 2 .4H 2 O. The reactants are preferably finely subdivided, although the monoammonium phosphate may alternatively be in the form of an aqueous slurry. Additional fertilizer ingredients such as nitrogenous compounds and/or potassium salts may be added to the reactant mixture. The granules obtained are preferably dried to remove excess moisture, and by heating at about 90‹ C. the magnesium ammonium phosphate is converted to the monohydrate state.