Patent GB-383278-A (GB)
Title: Process for the production of solid diammonium phosphate, and mixed salts containing same, from solutions of phosphoric acid
IPC: C05B7/00
Filed: 1931-07-25
Abstract: Solid di-ammonium phosphate or fertilizing mixtures containing it are obtained by introducing a solution, containing phosphoric acid either alone or in admixture with other fertilizing substances other than mineral acids, in a finely divided state into a current of a mixture of ammonia with air and other gases or gas mixtures in the proportion of not more than 1 mol. of phosphoric acid to 2 mols. of ammonia, whilst maintaining an elevated temperature not exceeding 60-70 DEG C. in the reaction zone, where-by the water is instantaneously evaporated and the resulting salt containing di-ammonium phosphate is obtained in powder form. The solution and the ammoniacal gas may be pre-warmed.  Atomizing devices such as nozzles, rotary nozzles, centrifuging devices, dispersion discs or the like may be employed and the air or other gas may be employed wholly or in part, under pressure, for atomizing the phosphoric acid.  Fertilizing mixtures or double salts containing potassium, sodium or ammonium nitrate, ammonium chloride, ammonium phosphate, ammonium sulphate and the like in addition to di-ammomium phosphate may be obtained by introducing these salts, in a dissolved and suspended condition, into the reaction chamber in admixture or along with the phosphoric acid solution.  Solutions obtained by treating raw phosphates with acids, e.g. nitric acid particularly after the addition of ammonium sulphate and the separation of calcium sulphate, may be employed.  The ammonia carried away in the effluent gases may be recovered by bringing them into contact with the phosphoric acid solution which is on its way to the reaction chamber.ALSO:Mixed fertilizers containing diammonium phosphate are obtained by introducing a solution containing phosphoric acid, alone or in admixture with solutions and/or suspensions of other fertilizing substances other than mineral acids, in a finely divided state into a current of a mixture of ammonia with air and/or other gases or gas mixtures in the proportion of not more than 1 mol. of phosphoric acid to 2 mols. of ammonia, whilst maintaining an elevated temperature not exceeding 60-70 DEG  C. in the reaction zone, whereby the water is instantaneously evaporated and the resulting mixture containing diammonium phosphate is obtained in powder form.  The solution and/or the ammoniacal gas may be prewarmed. Atomizing devices such as nozzles, rotary nozzles, centrifuging devices, dispersion discs and the like may be employed and the air and/or other gases may be employed wholly or in part under pressure for atomizing the phosphoric acid solutions. Fertilizing mixtures containing potassium, sodium or ammonium nitrate, ammonium chloride, ammonium phosphate, ammonium sulphate and the like in addition to diammonium phosphate are referred to. Solutions obtained by treating raw phosphates with acids, e.g. nitric acid, particularly after the addition of ammonium sulphate and the separation of the resulting calcium sulphate, may be employed.  The ammonia carried away in the effluent gases may be recovered by bringing them into contact with the phosphoric acid solution on its way to the reaction chamber.