METHOD OF PRODUCTION OF PHOSPHORUS-POTASSIUM FERTILIZERS Russian patent published in 2002 - IPC

FIELD: fertilizers. SUBSTANCE: invention relates to a method of production of complex phosphorus-potassium fertilizers of prolonged effect. Method of production of phosphorus-potassium fertilizers involves decomposition of phosphate raw with sulfuric acid or its mixture with phosphoric acid, mixing phosphate pulp with potash at pH = 3.1-7.5, granulation and drying the ready product. Before mixing the latter with potash phosphate pulp is neutralized preliminary taken in the amount 18.3-95% of its total mass with alkaline magnesium- containing component to mole ratio of added MgO to K₂O = (0.23-0.83) : 1 and treatment of obtained mixture with potash is carried out at pH = 7.6-8.5 followed by its mixing with remaining part of phosphate pulp. From 20% to 60% of K₂O in fertilizer composite is in citrate- soluble form that provides decrease of loss in potassium washing out from soil. Also, fertilizers comprise magnesium as a useful component. EFFECT: improved method of production, enhanced effectiveness of fertilizer. 1 tbl