GB410731A - Improvements in the manufacture and production of ammonium salts of phosphoric acid - Google Patents

Abstract

Ammonium phosphates or mixed fertilizers containing the same are produced by treating a solution containing phosphoric acid and nitric acid and/or nitrates, especially those of alkali metals or ammonium, with so much ammonia that the phosphoric acid, if necessary after cooling, is mainly or completely separated as triammonium phosphate, which is separated from the nitrate solution and, if desired, converted into mixed fertilizers. The invention is particularly applicable to solutions obtained by decomposing crude phosphate with nitric acid and precipitating calcium with soluble sulphates. The nitrate solution, after removing excess ammonia, may be worked up into solid nitrates or into mixed or complete fertilizers. The triammonium phosphate is preferably worked up into the di- or mono-salt, or a mixture thereof, the ammonia evolved being re-used, and these salts mixed, for example, with part of the ammonium nitrate obtained, and also, if desired, with potassium salts. Thus the triammonium phosphate may be added to a hot ammonium nitrate solution evaporated to a water content of 3--5 per cent. Potassium salts are mixed with the resulting pulp of diammonium phosphate and ammonium nitrate. According to one example, pebble phosphate is decomposed with nitric acid, and ammonium sulphate added to precipitate calcium sulphate. The solution is saturated with ammonia and cooled to-5 DEG C. to separate triammonium phosphate, which is added to part of the concentrated ammonium nitrate solution as described above. The remaining part is caused to solidify with calcium carbonate made by reacting the calcium sulphate with ammonium carbonate.ALSO:Ammonium phosphates or mixed fertilizers containing the same are produced by treating a solution containing phosphoric acid and nitric acid and/or nitrates, especially those of alkali metals or ammonium, with so much ammonia that the phosphoric acid, if necessary after cooling, is mainly or completely separated as triammonium phosphate, which is separated from the nitrate solution and, if desired, converted into mixed fertilizers. The invention is particularly applicable to solutions obtained by decomposing crude phosphate with nitric acid and precipitating calcium with soluble sulphates. The nitrate solution, after removing excess ammonia, may be worked up into solid nitrates or into mixed or complete fertilizers. The triammonium phosphate is preferably worked up into the di- or mono-salt, or a mixture thereof, the ammonia evolved being re-used, and these salts mixed, for example, with part of the ammonium nitrate obtained, and also, if desired, with potassium salts. Thus the triammonium phosphate may be added to a hot ammonium nitrate solution evaporated to a water content of 3-5 per cent. Potassium salts are mixed with the resulting pulp of diammonium phosphate and ammonium nitrate. According to one example, pebble phosphate is decomposed with nitric acid, and ammonium sulphate added to precipitate calcium sulphate. The solution is saturated with ammonia and cooled to -5 DEG C. to separate triammonium phosphate, which is added to part of the concentrated ammonium nitrate solution as described above. The remaining part is caused to solidify with calcium carbonate made by reacting the calcium sulphate with ammonium carbonate.