Patent GB-734887-A (GB)
Title: Improvements in and relating to the manufacture of phosphated fertilisers and fertilisers obtained thereby
IPC: C05B11/04
Filed: 1953-04-24
Abstract: In the manufacture of a phosphate fertiliser by attacking a natural calcium phosphate with a mineral acid followed by neutralization of the product, before the addition of the neutralising agent manganese ions are introduced into the mass resulting from the acid attack in the proportion of at least 20 gram atoms of manganese for every 100 gram molecules of P2O5 contained in the natural phosphate.  The preferred mineral acid is nitric acid and the neutralizing agent used may be lime, calcium carbonate or ammonia.  If nitric acid is employed, after the addition of the manganese ions to the mass resulting from the acid attack, sulphuric ions in the form of sulphuric acid or a sulphate, or phosphoric acid may be added before or during the neutralization so as to convert the calcium nitrate to calcium sulphate or phosphate.  Carbon dioxide gas may be employed for the same purpose during neutralization but in this case it is necessary to add the sulphuric ions in the form of sulphuric acid or as a sulphate such as gypsum, in an amount stoichiometrically equivalent to the quantity of manganese ion-already introduced. According to examples, (i) natural phosphate is attacked with hydrochloric acid and after stirring for two hours manganese carbonate is introduced followed by slaked lime.  When precipitation is complete the dicalcium phosphate is filtered off.  (ii) Gafsa phosphate is attacked by 48.6 per cent nitric acid and hydrated manganese sulphate is added to the paste obtained, then while stirring gaseous ammonia is introduced into the paste followed by carbon dioxide gas.  The resulting fertilizer contains 8.45 per cent of nitric nitrogen, 8.45 per cent of ammoniacal nitrogen and 12.7 per cent of phosphoric acid, 99.3 per cent of which is citrate soluble. The manganese sulphate may be replaced by manganese nitrate and gypsum.  (iii) Tunisian phosphate is attached with nitric acid, manganese nitrate added to the paste obtained, and then with agitation gaseous ammonia and sulphuric acid are introduced.  A fertilizer containing 7.8 per cent each of nitric and ammoniacal nitrogen with 11.7 per cent of phosphoric acid, 99.2 per cent of which is citrate soluble, is obtained.  (iv) Tunisian phosphate is attacked with nitric acid and manganese carbonate is added to the paste obtained, then with agitation gaseous ammonia and phosphoric acid are introduced.  The fertilizer obtained contains 8.0 per cent each of nitric and ammoniacal nitrogen and 22.6 per cent phosphoric acid of which 99.4 per cent is citrate soluble.ALSO:In the manufacture of a phosphate fertilizer by attacking a natural calcium phosphate with a mineral acid followed by neutralization of the product, before the addition of the neutralizing agent, manganese ions are introduced into the mass resulting from the acid attack in the proportion of at least 20 gram atoms of manganese for every 100 gram molecules of P2O5 contained in the natural phosphate.  The preferred mineral acid is nitric acid and the neutralizing agent used may be lime, calcium carbonate or ammonia.  If nitric acid is employed, after the addition of the manganese ions to the mass resulting from the acid attack, sulphuric ions in the form of sulphuric acid or a sulphate, or phosphoric acid may be added before or during the neutralization so as to convert the calcium nitrate to calcium sulphate or phosphate.  Carbon dioxide gas may be employed for the same purpose during neutralization but in this case it is necessary to add the sulphuric ions in the form of sulphuric acid or as a sulphate such as gypsum, in an amount stoichiometrically equivalent to the quantity of manganese ions already introduced. According to examples (i) natural phosphate is attacked with hydrochloric acid and after stirring for two hours manganese carbonate is introduced followed by slaked lime. When precipitation is complete, the dicalcium phosphate is filtered off; (ii) Gafsa phosphate is attacked by 48.6 per cent nitric acid and hydrated manganese sulphate is added to the paste obtained, then while stirring gaseous ammonia is introduced into the paste followed by carbon dioxide gas.  The resulting fertilizer contains 8.45 per cent of nitric nitrogen, 8.45 per cent of ammoniacal nitrogen and 12.7 per cent of phosphoric acid, 99.3 per cent of which is citrate soluble. The manganese sulphate may be replaced by manganese nitrate and gypsum; (iii) Tunisian phosphate is attacked with nitric acid, manganese nitrate added to the paste obtained, and then with agitation gaseous ammonia and sulphuric acid are introduced.  A fertilizer containing 7.8 per cent each of nitric and ammoniacal nitrogen with 11.7 per cent of phosphoric acid 99.2 per cent of which is citrate soluble, is obtained; (iv) Tunisian phosphate is attacked with nitric acid and manganese carbonate is added to the paste obtained, then with agitation gaseous ammonia and phosphoric acid are introduced.  The fertilizer obtained contains 8.0 per cent each of nitric and ammoniacal nitrogen and 22.6 per cent phosphoric acid of which 99.4 per cent is citrate soluble.