PURPOSE: To improve secondary combustion ratio and to prevent spout of molten slag by specifying diameter of spouting part of bottom blowing gas on the molten slag surface, diameter of spreading of O2 gas on the molten slag with top blowing lance, recessed depth of the molten slag with the top blowing oxygen, etc., at the time of producing molten iron with iron oxide and coal as reducing agent in an iron bath type smelting reduction furnace.
CONSTITUTION: Under condition of coexisting molten iron (molten pig) 4 and the molten slag 5 in the converter type refining furnace 1 having the bottom blowing tuyeres 2 and the oxygen top blowing lance 2, while blowing N2 or O2 from the bottom blowing tuyeres 2 and blowing oxygen from the top blowing lance 3, the iron oxide 6 and the coal 7 as reducing agent are charged from the furnace top part and the iron oxide is reduced to produce the molten pig 4. In this case, at the time of using l1 for the diameter spouting with the bottom blowing gas on the surface of the molten slag 5 and D for inner diameter, the relation between both is specified so as to become 0.6D<l1<0.9D, and at the time of using l2 for the diameter spreading with the top blowing oxygen in the surface of the molten slag 5, it is specified so as to become l2<0.8l1. Further, relation between the recessed depth Ls of the molten slag 5 with the top blowing O2 and thickness Hs of the molten slag 5, is held so as to become Ls<Hs. The iron oxide is reduction-refined under high secondary combustion ratio and low spout of the molten slag.
SATO MITSURU
ISHIKAWA HIDEKI
SAITO TSUTOMU
HIRATA HIROSHI
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