| 摘要 |
PROBLEM TO BE SOLVED: To optimize and stabilize the furnace heat of a blast furnace, to reduce the fuel ratio and to improve the productivity, by securing the air permeability and reducibility of a cohesion zone formed by sintered ore when a large amount of pulverized coal is blown into the furnace, increasing O/C(ore-to-coke ratio) in the peripheral part of the furnace, improving the reducing efficiency of the same region, further reducing the temperature of molten iron flowing out from a tap hole and also reducing the variation thereof. SOLUTION: The basicity of sintered ore (CaO/SiO2) is held to 1.2 to 1.4, the content of SiO2 to 3.5 to 5.5 mass%, Al2O3 to 1.5 to 2.3 mass%, and MgO to 0.2 to 1.5 mass% each in a proper range. Further, the range of CaO/SiO2 in the sintered ore is extended, a part of the sintered ore is replaced with lumpy iron ore and/or a lumpy indirect raw material, and CaO/SiO2, SiO2, Al2O3 and MgO in the sintered ore and lumpy iron ore and/or lumpy indirect raw material are held in the proper ranges. Moreover, powdery iron ore and/or a powdery assistant raw material is blown into the furnace from a tuyere part.
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