METHOD OF PRODUCING COMPOUND FERTILISERS Russian patent published in 2011 - IPC C05G1/06 C01C1/24 

FIELD: chemistry.

SUBSTANCE: invention relates to production of compound fertilisers which contain nitrogen, phosphorus, potassium and sulphur and are used in agriculture. The method involves mixing wet-process phosphoric acid with absorptive liquid, step-by-step neutralisation of phosphoric acid and 92-95% sulphuric acid with ammonia while feeding acid separately during the three steps, adding a nitrogen-containing component in form of ammonium sulphate solution to the pulp in an amount necessary for maintaining the volumetric consumption ratio of the solution: phosphoric acid equal to 0.06-0.18:1, granulating and drying the product. At the first step, the mixture of phosphoric acid and absorptive liquid is neutralised to obtain pulp with molar ratio NH₃/H₃PO₄ equal to 0.2-0.5 and density 1.37-1.43 t/m. At the second step, the pulp and sulphuric acid are post-neutralised in the tubular reactor to obtain sulphoammophos pulp with molar ratio NH₃/H₃PO₄ equal to 0.7-0.9. Sulphuric acid is fed in an amount necessary for maintaining the ratio SO₃:P₂O₅ in the sulphoammophos pulp equal to 0.6-2.0:1. At the third step, final neutralisation of the sulphoammophos pulp is carried out in a granulator-ammoniator. During production of NPK fertiliser, potassium chloride is fed into the granulator-ammoniator in amount of 1-20% of the weight of the product in terms of K₂O.

EFFECT: invention lowers consumption of sulphuric acid by 4-10%, enables to obtain a wide range of NP and NPK fertilisers with good application properties and having antiseptic properties.

2 cl, 1 tbl, 4 ex