GB353763A - Improvements in and relating to the manufacture of fertilisers - Google Patents

Abstract

Phosphoric acid; calcium and potassium nitrates; ammonium phosphates.--Fertilizers are obtained from phosphate rock and potassium salts by dissolving phosphate rock in nitric acid, crystallizing calcium nitrate from the resulting solution, converting all or part of the calcium nitrate by means of potassium salts into potassium nitrate, mixing a convenient portion of the potassium nitrate with the mother liquors from the crystallization of calcium nitrate, neutralizing the mixture with ammonia and drying the product. The potassium salts referred to are the sulphate and chloride. The mother liquor may be freed from its remaining calcium by precipitation with reagents such as hydrofluoric acid, sulphuric acid, ammonium or potassium fluoride, ammonium or alkali sulphates or bisulphates prior to its further treatment, the calcium precipitates being used in known manner to regenerate the reagent. The mixture or solution of potassium nitrate and phosphoric acid containing mother liquor is preferably brought to dryness during the neutralizing reaction with ammonia, the mixture being injected into, or subjected to stirring in, an apparatus into which gaseous ammonia is introduced under such conditions that the water present is evaporated by the heat developed, with if necessary a further supply of heat so that a dry product is obtained capable of continuous removal. The amount of calcium nitrate separated by crystallization may be limited so that the product contains di-calcium phosphate. Specifications 339,340 and 339,969, [both in Class 1 (ii), Inorganic compounds, other than &c.], are referred to.ALSO:Fertilizers are obtained from phosphate rock and potassium salts by dissolving phosphate rock in nitric acid, crystallizing calcium nitrate from the resulting solution, converting all or part of the calcium nitrate by means of potassium salts into potassium nitrate, mixing a convenient portion of the potassium nitrate with the mother liquors from the crystallization of calcium nitrate, neutralizing the mixture with ammonia and drying the product. The potassium salts referred to are the sulphate and chloride. The mother liquor may be freed from its remaining calcium by precipitation with reagents such as hydrofluoric acid, sulphuric acid, ammonium or potassium fluoride, ammonium or alkali sulphates or bisulphates prior to its further treatment, the calcium precipitates being used in known manner to regenerate the reagent. The mixture or solution of potassium nitrate and phosphoric acid containing mother liquor is preferably brought to dryness during the neutralizing reaction with ammonia, the mixture being injected into, or subjected to stirring in, an apparatus into which gaseous ammonia is introduced under such conditions that the water present is evaporated by the heat developed, with if necessary a further supply of heat so that a dry product is obtained capable of continuous removal. The amount of calcium nitrate separated by crystallization may be limited so that the product contains di-calcium phosphate. Specifications 339,340 and 339,969, [both in Class 111, Sewage &c.], are referred to.