Material for phosphate fertilizer and method for production thereof

A raw material for phosphate fertilizer consisting essentially of a slag which contains phosphate formed in a dephosphorization reaction in molten iron, the phosphate content satisfying the formula (2)

• [P2O5]≧5.6×[F]+10 (2)
• where, [P2O5] is the phosphate content in slag, (mass %), and [F] is the fluorine content in slag, (mass %).

A method for manufacturing raw material for phosphate fertilizer, comprising the steps of:

• charging a CaO source and an oxygen source to a molten iron containing 0.07 mass % or less Si to induce dephosphorization reaction in the molten iron;
• and recovering a slag, which contains phosphate generated by the dephosphorization reaction, as the raw material for phosphate fertilizer.

A method for manufacturing raw material for phosphate fertilizer, comprising the steps of charging a CaO source and an oxygen source into a vessel holding a molten iron therein to induce dephosphorization reaction in the molten iron, and recovering a slag, which contains phosphate generated by the dephosphorization reaction, as the raw material for phosphate fertilizer;

• at least a part of a gas oxygen and of the CaO source being blown against the surface of molten iron bath via a top-blow lance to induce dephosphorization reaction in the molten iron;
• and the charge rate B (kg/min/ton-molten iron) of the CaO source blown against the surface of molten iron bath, converted to CaO, satisfying the formula (3) in relation to the charge rate A (Nm3/min/ton-molten iron) of the oxygen source charged into the vessel, converted to gas oxygen:
• 0.3≦A/B≦7 (3)

A method for manufacturing raw material for phosphate fertilizer, comprising the steps of charging a CaO source and an oxygen source into a pot type vessel or a torpedo car type vessel, holding a molten iron therein, to induce dephosphorization reaction in the molten iron, and recovering a slag, which contains phosphate generated in the dephosphorization reaction, as the raw material for phosphate fertilizer;

• at least a part of a gas oxygen and of the CaO source being blown against the surface of molten iron bath via a top-blow lance, and a gas which contains a powder being blown into the molten iron via an immersion lance and/or a blowing nozzle.

A method for manufacturing phosphate fertilizer using the raw material for phosphate fertilizer manufactured by the method according to any one of claims 10 to 24.