GB762622A - Process for the manufacture of phosphorus-nitrogen and phosphorus-nitrogen-potassium fertilizers in a granular condition - Google Patents

Abstract

Granular anhydrous phosphorus-nitrogen fertilizers are prepared by treating solid monocalcium phosphate or powdered products containing it, in a rotating reaction vessel first with sulphuric acid and water in a proportion by weight such that 1 part of P2O5 of the monocalcium phosphate there are added two parts by weight of sulphuric acid (H2SO4) and a quantity of water such as a total in the mixture 1.7 parts by weight and thereafter reacting and absorbing 0.85 parts by weight of gaseous ammonia. The monocalcium phosphate starting material may be that contained in calcium superphosphate or triple superphosphate or mixtures thereof. Further fertilizing ingredients containing ammoniacal nitrogen or potassium which do not react either with sulphuric acid or ammonia may be incorporated during the reaction. According to examples (1) calcium superphosphate and sulphuric acid were charged to a rotatable drum in amounts such that the weight ratio P2O5:H2SO4: H2O was 1:2:1.7. The drum was then rotated to homogenize the mass after which a weight of gaseous ammonia half of that of the total water was added while continuing rotation; an anhydrous granular product resulted, 90 per cent of which was between 1.5 and 3.5 mm in size. Fines were recycled to the reaction drum. (2) A phosphorus-nitrogen-potassium fertilizer was prepared by treating calcium superphosphate and potassium sulphate with sulphuric acid and, as in Example 1, treating the mixture with gaseous ammonia A further example illustrates the use of calcium superphosphate and triple superphosphate starting material to which was added potassium sulphate and ammonium sulphate with the sulphuric acid after which ammonia was reacted and absorbed as before.ALSO:Granular anhydrous phosphorus-nitrogen fertilisers are prepared by treating solid monocalcium phosphate or powdered products containing it, in a rotating reaction vessel first with sulphuric acid and water in a proportion by weight such that 1 part of P2O5 of the mono-calcium phosphate there are added two parts by weight of sulphuric acid (H2SO4) and a quantity of water such as total in the mixture 1,7 parts by weight and thereafter reacting and absorbing 0,85 parts by weight of gaseous ammonia. The monocalcium phosphate starting material may be that contained in calcium superphosphate or triple superphosphate or mixtures thereof. Further fertilizing ingredients containing ammoniacal nitrogen or potassium which do not react either with sulphuric acid or ammonia may be incorporated during the reaction. According to examples (1) calcium superphosphate and sulphuric acid were charged to a rotatable drum in amounts such that the weight ratio P2O5 : H2SO4 : H2O was 1 : 2 : 1,7. The drum was then rotated to homogenise the mass after which a weight of gaseous ammonia half of that of the total water was added while continuing rotation; an anhydrous granular product resulted 90 per cent of which was between 1,5 and 3,5 mm. in size. Fines were recycled to the reaction drum. (2) A phosphorus-nitrogen-potassium fertilizer was prepared by treating calcium superphosphate and potassium sulphate with sulphuric acid and, as in Example 1, treating the mixture with gaseous ammonia. A further example illustrates the use of calcium superphosphate and triple superphosphate starting material to which was added potassium sulphate and ammonium sulphate with the sulphuric acid after which ammonia was reacted and absorbed as before.