GB584866A - Improvements in and relating to phosphatic fertilizers - Google Patents

Abstract

Slow-acting phosphatic fertilizers are produced by treating a phosphatic material such as phosphate rock with a substance or a mixture of substances (other than sulphuric acid or ammonium sulphate above), such that a calcium hydrogen phosphate is formed, and subsequently heating the product between 250 DEG and 600 DEG C. for a period of 1/2 to 1 hour. Reacting agents specified are phosphoric and other phosphoruscontaining acids, hydrochloric and nitric acids with or without sodium or potassium salt, which may be employed in proportions ranging from that theoretically needed to give 80 per cent. conversion to CaHPO4 to that theoretically needed to give 100 per cent. conversion to Ca-(H2 PO4)2, plus an additional amount necessary to react with all impurities. When phosphoric acid is employed, the amount used is between 1 and 4 mols. per mol. P2O5 in the phosphate rock. The product has a relatively low fluorine content. According to the Provisional Specification the heating may take place at temperatures in excess of 200 DEG C., and the reacting agents may comprise mixtures of ammonium, sodium, or potassium sulphates, either by themselves or with the specified acids.ALSO:Slow-acting phosphatic fertilizers are produced by treating a phosphatic material such as phosphate rock with a substance or a mixture of substances (other than sulphuric acid or ammonium sulphate used alone), such that a calcium hydrogen phosphate is formed, and subsequently heating the product to between 250 DEG and 600 DEG C. for a period of 1/2 to 1 hour. Reacting agents specified are phosphoric and other phosphorous-containing acids, hydrochloric and nitric acids with or without potassium and sodium salts, which may be employed in proportions ranging from that theoretically needed to give 80 per cent. conversion to Ca HPO4 to that theoretically needed to give 100 per cent conversion to Ca (H2 PO4)2, plus an additional amount necessary to react with all impurities. When phosphoric acid is employed, the amount used is between 1 and 4 moles per mole P2 O5 in phosphate rock. The product has a relatively low fluorine content. According to the Provisional Specification, the heating may take place at temperatures in excess of 200 DEG C., and the reacting agents may comprise mixtures of ammonium, sodium, or potassium sulphates, either by themselves or with the specified acids.