Patent GB-361518-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: Ammonium phosphates and nitrate; nitric acid; calcium and potassium nitrate.--Rock phosphate is dissolved in nitric acid, from approximately 20 per cent to approximately 60 per cent of the calcium nitrate is separated by crystallization, and potassium sulphate is added to the resulting mother liquor to convert the remaining calcium nitrate into potassium nitrate and, after separating the calcium sulphate formed, the remaining solution is neutralized with ammonia and brought to dryness to produce a fertilizer.  The amount of potassium sulphate added may be only sufficient to convert a part of the calcium nitrate present so that the subsequent addition of ammonia results in the production of some di-calcium phosphate or the conversion of all the phosphoric acid present into this form.  The calcium sulphate precipitate may be washed in counter-current in a Dorr apparatus, the dilute wash liquid being utilized in the process or employed to absorb nitrous gases in towers for producing nitric acid for the process.  The neutralization with ammonia may be carried out to give monoammonium phosphate or di-ammonium phosphate or an average of these two products.  If excess nitric acid is used in the initial treatment of the rock phosphate it appears in the product as ammonium nitrate.  The solutions may be atomized and brought into contact with ammonia in countercurrent, a dry product being immediately obtained.  Necessary evaporations are preferably carried out under vacuum.  Examples are given. Specifications 339,340, 339,969, [both in Class 1 (ii), Inorganic compounds, other than &c.], and 353,763 are referred to.ALSO:Rock phosphate is dissolved in nitric acid, from approximately 20 per cent to approximately 60 per cent of the calcium nitrate is separated by crystallization, and potassium sulphate is added to the resulting mother liquor to convert the calcium nitrate into potassium nitrate and after separating the calcium sulphate formed, the remaining solution is neutralized with ammonia and brought to dryness to produce a fertilizer.  The amount of potassium sulphate added may be only sufficient to convert a part of the calcium nitrate present so that the subsequent addition of ammonia results in the production of some di-calcium phosphate or the conversion of all the phosphoric acid present into this form. The calcium sulphate precipitate may be washed in countercurrent in a Dorr apparatus, the dilute wash liquid being utilized in the process or employed to absorb nitrous gases in towers for producing nitric acid for the process.  The neutralization with ammonia may be carried out to give mono-ammonium phosphate or di-ammonium phosphate or an average of these two products.  If excess nitric acid is used in the initial treatment of the rock phosphate it appears in the product as ammonium nitrate.  The solutions may be atomized and brought into contact with ammonia in counter-current, a dry product being immediately obtained. Necessary evaporations are preferably carried out under vacuum. Examples are given.  Specifications 339,340, 339,969, [both in Class 111, Sewage &c.], and 353,763 are referred to.