Patent GB-761249-A (GB)
Title: Improved process for the preparation of superphosphates and compound fertilisers
Inventor: STEICHEN ADOLPHE FERDINAND
IPC: C05C1/00
Filed: 1953-10-20
Abstract: Superphosphates are manufactured by attacking a ground mineral phosphate with a mineral acid or acids to which is added at least one compound reacting exothermically with said acid(s).  These reactants are mixed for less than a second, preferably less 1/4 second and then passed to a reaction zone (the "den") where reaction is completed with the assistance of the exothermic heat of reaction between the acid(s) and the compound(s). Specified acids are sulphuric acid; and, in a preferred embodiment, a mixture of sulphuric and dilute phosphoric acid resulting from the washing of the insoluble materials obtained in the manufacture of phosphoric acid, the latter being also the exothermically reacting compound.  Specified exothermically reacting compounds are potassium hydroxide and/or potassium salts such as carbonate and chloride, ammonia, and a final product may contain fertilizing salts, e.g. sulphates or phosphates of magnesium, potassium or ammonium formed in situ.  Natural-, waste- and by-products which react exothermically and contain or form by reaction the desired elements or radicals may alternatively be used. If desired the acid and exothermically reacting compound, e.g. the dilute nitric acid may be mixed prior to addition of the superphosphate, the temperature of this preliminary reaction assisting the acid attack: in examples gaseous ammonia is first mixed with sulphuric acid.  The products are dry and granulable.  Loss of heat from the mixing and reaction zones should be avoided, e.g. by insulation or by protecting from air currents Examples are given in which mixing temperatures of 65 DEG C. and 95 DEG C. and reaction zone temperatures of up to 114C DEG ., are used.  Specification 687,741 is referred to.ALSO:Binary, ternary or polyfunctional compound or complex fertilizers are manufactured by attacking a ground mineral phosphate with a mineral acid or acids to which is added at least one compound reacting exothermically with said acid(s).  These reactants are mixed for less than a second, preferably less than 1/4 second and then passed to a reaction zone (the "den") where reaction is completed with the assistance of the exothermic heat of reaction between the acid(s) and the compound(s). Specified acids are sulphuric acid; and, in a preferred embodiment, a mixture of sulphuric and dilute phosphoric acid resulting from the washing of the insoluble materials obtained in the manufacture of phosphoric acid, the latter being also the exothermically reacting compound.  Specified exothermically reacting compounds are potassium hydroxide and/or potassium salts such as carbonate and chloride, ammonia and a final product may contain fertilizing salts e.g. sulphates or phosphates of magnesium, potassium or ammonium formed in situ.  Natural-, waste-and by-products which react exothermically and contain or form by reaction the desired elements or radicals may alternatively be used.  If desired the acid and exothermically reacting compound e.g. the dilute nitric acid may be mixed prior to addition of the superphosphate, the temperature of this preliminary reaction assisting the acid attack: in examples gaseous ammonia is first mixed with sulphuric acid.  The products are dry and granulable.  Loss of heat from the mixing and reaction zones should be avoided e.g. by insulation or by protecting from air currents. Examples are given in which mixing temperatures of 65 DEG C. and 95 DEG C. and reaction zone temperatures of up to 114 DEG C., are used. Specification 687,741 [Group III] is referred to.