GB1480486A - Ammonium phosphate - Google Patents

Abstract

1480486 Ammonium phosphate SCOTTISH AGRICULTURAL INDUSTRIES Ltd 9 May 1975 [16 May 1974] 21747/74 Heading C1A A particulate solid comprising ammonium phosphate of N : P atomic ratio 0À95 to 1À6 is made by a process which comprises partially ammoniating wet-process phosphoric acid to a N : P atomic ratio not greater than 0À3, the acid having a Mg content greater than 0À2%, preferably in a scrubber unit, treating the partially-ammoniated wet-process phosphoric acid with ammonia to produce a fluid slurry of ammonium phosphate, adding a soluble source of fluorine to increase the fluorine level of the slurry, the amount added providing 0À1-5% of fluorine and removing excess water to give a water level of 3À5-15% by weight. The preferred fluorine-containing compound is NH 4 HF 2 . Silicofluorides may be precipitated out prior to the first ammoniating step by adding cations, and the silicofluorides returned to the fluid slurry prior to the water-removal step. The slurry temperature is preferably 120- 126‹ C. In a preferred embodiment the partially ammoniated acid (N : P=0À3) and gaseous NH3 are added to a slurry of ammonium phosphate (N : P 1À2-1À8) with a moisture content in the range 10-20% by weight, in such proportions as to form more slurry of the same composition, adding the fluorine source, simultaneously removing an amount of slurry equivalent to that being formed and mixing the removed slurry with phosphoric acid to produce the desired N : P atomic ratio and evaporating off excess moisture. Reference has been directed by the Comptroller to Specification 951,476.