Patent GB-359680-A (GB)
Title: Improvements in and relating to the treatment of phosphate rock and the manufacture of fertilisers
IPC: C05B11/06
Filed: 1930-10-08
Abstract: Phosphoric acid; ammonium chloride, sulphate, phosphate, and salts in general; calcium nitrate and phosphates; potassium nitrate.--Phosphate rock is dissolved in nitric acid and the resulting solution is divided into two portions.  As much as possible of the calcium nitrate present in the first portion is separated by crystallization leaving a liquor consisting mainly of phosphoric acid.  Some of the calcium nitrate is also separated from the second portion but sufficient is left in the mother liquor to form di-calcium phosphate with the phosphoric acid present whereupon ammonia is added to the mother liquor to precipitate the dicalcium phosphate which is separated, the remaining solution containing ammonium nitrate being reacted with potassium salts such as potassium chloride or sulphate to form potassium nitrate which is separated and a solution of ammonium salts such as ammonium chloride or sulphate. The resulting potassium nitrate is added to the other mother liquor containing phosphoric acid and the mixture is neutralized with ammonia and dried to produce a fertilizer.  The mother liquor from the first portion may be freed from the small quantity of remaining lime by precipitation before the subsequent treatment.  The mixture of phosphoric acid and potassium nitrate may be neutralized by distributing it in an atmosphere of ammonia gas a dry product being directly obtained.  Any excess of nitric acid used in dissolving the phosphate rock appears in the final product as ammonium nitrate.  A portion of the di-calcium phosphate may also be added to the fertilizer or may be mixed with the calcium nitrate obtained and a portion of the potassium nitrate and if desired urea to produce a further fertilizer with an alkaline reaction.  The di-calcium phosphate may be returned to be treated with nitric acid together with fresh phosphate rock; previous to such treatment, it may be treated with ammonia or ammonium carbonate which produces a solution of di-ammonium phosphate and converts it into tri-calcium phosphate or a mixture of di-calcium phosphate and calcium carbonate.  The calcium nitrate may be reacted with potassium salts to produce potassium nitrate. Specification 339,340, [Class 1 (ii), Inorganic compounds, other than &c.], is referred to.  The Specification as open to inspection under Sect. 91 (3) (a) comprises also a process in which the whole of the solution of rock phosphate in nitric acid is treated in the manner referred to above for treating the second portion, all the phosphoric acid being precipitated as di-calcium phosphate.  The remaining solution of ammonium nitrate being converted wholly or partially with potassium chloride to form potassium nitrate and the products being mixed.  This subject-matter does not appear in the Specification as accepted.ALSO:Phosphate rock is dissolved in nitric acid and the resulting solution is divided into two portions.  As much as possible of the calcium nitrate present in the first portion is separated by crystallization leaving a liquor consisting mainly of phosphoric acid.  Some of the calcium nitrate is also separated from the second portion but sufficient is left in the mother liquor to form di-calcium phosphate with the phosphoric acid present whereupon ammonia is added to the mother liquor to precipitate the dicalcium phosphate which is separated, the remaining solution containing ammonium nitrate being reacted with potassium salts such as potassium chloride or sulphate to form potassium nitrate which is separated and a solution of ammonium salts such as ammonium chloride or sulphate.  The resulting potassium nitrate is added to the other mother liquor containing phosphoric acid and the mixture is neutralized with ammonia and dried to produce a fertilizer.  The mother liquor from the first portion may be freed from the small quantity of remaining lime by precipitation before the subsequent treatment.  The mixture of phosphoric acid and potassium nitrate may be neutralized by distributing it in an atmosphere of ammonia gas, a dry product being directly obtained. Any excess of nitric acid used in dissolving the phosphate rock appears in the final product as ammonium nitrate.  A portion of the di-calcium phosphate may also be added to the fertilizer or may be mixed with the calcium nitrate obtained and a portion of the potassium nitrate and if desired urea to produce a further fertilizer with an alkaline reaction.  The di-calcium phosphate may be returned to be treated with nitric acid together with fresh phosphate rock; previous to such treatment, it may be treated with ammonia or ammonium carbonate which produces a solution of di-ammonium phosphate and converts it into tri-calcium phosphate or a mixture of di-calcium phosphate and calcium carbonate.  The calcium nitrate may be reacted with potassium salts to produce potassium nitrate.  Specification 339,340, [Class 111, Sewage &c.], is referred to.  The Specification as open to inspection under Sect. [91 (3) (a) comprises also a process in which the whole of the solution of phosphate rock in nitric acid is treated in the manner referred to above for treating the second portion, all the phosphoric acid being precipitated as di-calcium phosphate, the remaining solution of ammonium nitrate being converted wholly or partially with potassium chloride to form potassium and the products being mixed.  This subject-matter does not appear in the Specification as accepted.