GB371437A - Improvements in or relating to the manufacture and production of fertilisers - Google Patents

Abstract

A solid fertilizer is directly obtained by treating rock phosphate with an ammonium-sulphate sulphuric-acid solution in which the ratio of free acid to water corresponds to an acid concentration of at least 54 DEG B<\>ae, and ammoniating the resulting solid product with ammonia. The ammoniation may be carried out in stages and the ammonia may be aqueous or anhydrous gaseous or liquid ammonia. When the solid intermediate product is to be treated with anhydrous ammonia sulphuric acid of 54-60 DEG B<\>ae may be used for the acid treatment but when the solid intermediate product is to be treated with aqueous ammonia sulphuric acid of 64-66 DEG B<\>ae may be used. The quantity of sulphuric acid used may be sufficient to react with the non-phosphatic ingredients of the rock and to convert the tricalcium phosphate in the rock to monocalcium phosphate. The ammonium-sulphate sulphuric acid solution, which may contain 1/5 -\ba1/2 molecular proportion of ammonium sulphate per molecular proportion of sulphuric acid, may be prepared by partially neutralizing sulphuric acid with anhydrous liquid or gaseous ammonia or even with aqueous ammonia if the amount of water introduced is not too great. Other fertilizing or inert materials may be added before or after the treatment with sulphuric acid or subsequent ammoniations. Specifications 239,551, [Class 111, Sewage &c.], 340,120, 347,974, and 359,020 are referred to. According to the Specification as open to inspection under Sect. 91 (3) (a) the solid intermediate product may be used as a fertilizer without ammoniation. This subject-matter does not appear in the Specification as accepted.