Patent GB-442395-A (GB)
Title: An improved process for the production of di-calcium phosphate or of mixed fertilisers containing the same
IPC: C05B3/00
Filed: 1935-01-23
Abstract: Di-calcium phosphate or mixed fertilizers containing it are obtained by reacting mono-calcium phosphate or mixtures containing it and other salts with an ammonium phosphate solution in which the molecular ratio NH3 : P2O5 is equal to or greater than 2 : 1, the mother liquor being circulated in a closed cycle and having its molecular ratio NH3 : P2O5 restored to its original value by the addition of ammonia after each treatment of the mono-calcium phosphate &c.  By selecting the conditions it is possible to cause precipitation of either di-calcium phosphate alone or a mixture thereof with an ammonium phosphate.  The initial materials specified include super-phosphate, double superphosphate and nitrophosphates. According to examples: (1) moist mono-calcium phosphate is covered with a saturated solution of di-ammonium phosphate at 20 DEG  C., a mixture of di-calcium phosphate and mono-ammonium phosphate being obtained and the mother liquor being restored to its original composition by the addition of ammonia for further use in the process; (2) a mixture of freshly prepared superphosphate and potassium chloride is stirred into a solution arising in the process which has been restored to a NH3 : P2O5 ratio of 4 : 1 by the addition of ammonia, the product obtained after filtering containing 7,8 per cent P2O5 and 10 3 per cent K2O and the liquor being restored to its original composition for further employment by the addition of ammonia.  The Specification as open to inspection under Sect. 91 comprises also intimately mixing phosphates of calcium and ammonium while still moist to produce mixtures of di-calcium phosphate and various ammonium phosphates.  This subject-matter does not appear in the Specification as accepted.ALSO:Mixed fertilizers containing di-calcium phosphate are obtained by reacting mono-calcium phosphate or mixtures containing it and other salts with an ammonium phosphate solution in which the molecular ratio NH3 : P2O5 is equal or greater than 2 : 1, the mother liquor being circulated in a closed cycle and having its molecular ratio NH3 : P2O5 restored to its original value by the addition of ammonia after each treatment of the mono-calcium phosphate &c.  By selecting the conditions it is possible to cause precipitation of a mixture of di-calcium phosphate with an ammonium phosphate.  The initial materials specified include super-phosphate, double superphosphate and nitrophosphates.  According to examples: (1) moist mono-calcium phosphate is covered with a saturated solution of di+ ammonium phosphate at 20 DEG  C., a mixture of di-calcium phosphate and mono-ammonium phosphate being obtained and the mother liquor being restored to its original composition by the addition of ammonia for further use in the process; (2) a mixture of freshly prepared superphosphate and potassium chloride is stirred into a solution arising in the process which has been restored to a NH3 : P2O5 ratio of 4 : 1 by the addition of ammonia, the product obtained after filtering containing 7,8 per cent P2O5 and 10,3 per cent K2O and the liquor being restored to its original composition for further employment by the addition of ammonia.  The Specification as open to inspection under Sect. 91 comprises also intimately mixing phosphates of calcium and ammonium while still moist to produce mixtures of dicalcium phosphate and various ammonium phosphates.  This subject-matter does not appear in the Specification as accepted.