METHOD OF PRODUCING COMPOUND FERTILISER Russian patent published in 2011 - IPC C05G1/06 

FIELD: chemistry.

SUBSTANCE: invention relates to production of compound mineral fertiliser used in agriculture. The method involves step-by-step neutralisation of phosphoric and sulphuric acid with ammonia while feeding the acids separately, post-neutralisation of the pulp in a tubular reactor, separation of vapour from the pulp, granulation and drying the obtained product. The acids are neutralised successively in three steps. The phosphoric acid used at the first neutralisation step is a mixture of evaporated and non-evaporated phosphoric acid obtained from processing stripped phosphorites which are pre-mixed in amounts required for achieving P₂O₅ concentration of the mixture of 32-34%. Further, the mixture is mixed with absorptive liquid until achieving density of the reaction mixture of 1.37-1.43 t/m³ and then neutralised to obtain pulp with molar ratio NH₃/H₃PO₄ equal to 0.2-0.5. 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 and ratio SO₃:P₂O₅ equal to 0.06-2.2:1. At the third step, final neutralisation of the sulphoammophos pulp is carried out in a granulator-ammoniator. During production of NPK fertiliser, potassium chloride or potassium sulphate is fed into the granulator-ammoniator.

EFFECT: invention enables to obtain a wide range of fertilisers, lowers power consumption and corrosive effect of aggressive media on equipment.

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