METHOD FOR PRE-REFINING MOLTEN IRON

PROBLEM TO BE SOLVED: To restrain the dusting with desiliconizing treatment and to realize the high desiliconizing efficiency by adjusting the injecting quantity of desiliconizing agent, particularly, a solid/air ratio according to the pressure of atmosphere surrounding a tilting trough. SOLUTION: On the way of charging molten iron 1 into a torpedo car 3 from the tilting trough 2 after once receiving the molten iron 1 from a blast furnace into the tilting trough 2, the desiliconizing agent 5 is injected into the molten iron 1 from a desiliconizing lance 4 directed to the molten iron 1 in the tilting trough 2 to execute the desiliconizing treatment. Thereat, the pressure of the atmosphere 6 surrounding the tilting trough 2 is measured with a pressure gage 7 and the injecting quantity of the desiliconizing agent and the solid/gas ratio are set according to this measured result. The pressure of the injecting atmosphere is risen as the injecting quantity of the desiliconizing agent is ripen, and when this pressure becomes >=0 mm Aq., the leakage of dusting is developed. The pressure of the injecting atmosphere is controlled to in the range of