PURPOSE: To improve reducing speed of iron ore and also secondary combustion ratio by specifying molten slag quantity in a furnace, remaining carbon quantity in the furnace and pressure of oxygen jet from to blowing lance at the time of reduction-refining molten pig by charging the iron ore and coal as reducing agent and blowing oxygen from top blowing lance into a iron bath type reduction furnace.
CONSTITUTION: Under condition of remaining the molten pig 4 and the molten slag 5 in the converter type refining furnace 1 providing bottom blowing tuyeres 2 and the oxygen top blowing lance 3, the iron ore and the coal as the reducing agent are charged from the furnace top part and oxygen gas is blown from the top blowing lance 3 and inert gas, oxygen gas, etc., are blown from the bottom blowing tuyeres 2 and iron ore is reduced, to produce the molten pig. In this case, ≥50% of the whole quantity of oxygen for blowing is blown from the top blowing lance 3 and the balance is blown from the bottom blowing tuyeres 2. Further, the refining furnace is operated under condition that the quantity of the molten slag 5 in the refining furnace is made to ≥500kg/m2 of cross section area of the furnace and the remaining carbon quantity in the furnace is made to ≥5wt.% of the molten slag and also cavity depth Ls of the molten slag by oxygen jet of the top blowing lance 3 is made to ≤0.7 of thickness Hs of the molten slag.
KATAYAMA HIROYUKI
MATSUO MITSUTAKA
SATO MITSURU
SAITO TSUTOMU
HIRATA HIROSHI
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