Process for producing molten iron

Abstract

A high purity of molten iron is produced efficiently at a higher productivity, by feeding a raw material mixture containing a carbonaceous reducing agent, an iron oxide-containing material and a CaO-containing material onto a hearth of a moving-hearth reducing furnace, heat-reducing the raw material mixture in the reducing furnace, and melting it in a melting furnace melting, wherein a blending amount of the CaO-containing material in the raw material mixture is adjusted in such a manner that another feeding of the CaO-containing material into the melting furnace makes a basicity of a slag generated in the melting furnace 1.1 or more an feeding amount of the CaO-containing material becomes 40 kg or less per ton of the molten iron obtained in the melting furnace.

Description

FIELD OF THE INVENTION [0001] The present invention relates to a method of producing a molten iron, more specifically, a method of producing a molten iron by heat-reducing an iron oxide-containing material such as iron ore together with a carbonaceous reducing agent such as carbonaceous material in a moving-hearth reducing furnace and then melting a reduced iron obtained in a melting furnace in particular, which is improved to produce a high purity of molten iron efficiently at a higher productivity. DESCRIPTION OF THE RELATED ART [0002] As one of the recently developed direct iron making methods, known is a method of producing a molten iron by beat-reducing in a rotary type moving-hearth reducing furnace a mixture containing an iron oxide-containing material (iron source) such as iron ore and a carbonaceous reducing agent such as carbonaceous material, or a compact of the mixture containing carbonaceous material in a shape of pellet, briquette or the like, and then finally reducing...

AI Technical Summary

Benefits of technology

[0007] In practicing the above method, it is preferable to further comprise: feeding a powdery carbonaceous material onto the hearth of the moving-hearth reducing furnace as a hearth material; and then feeding the raw material mixture containing a carbonaceous reducing agent, an iron oxide-containing material and a CaO-containing material onto the hearth material. At the time, it is preferable to make an amount of the carbonaceous material fed as the hearth material, 30 kg or more per ton of the molten iron obtained in the melting furnace, for effectively increasing the metallization ratio of the solid reduced iron obtained in the reducing furnace.

[0008] It is also preferable to blend the CaO-containing material, whose entire amount is sufficient for making the basicity of the slag generated in the melting furnace 1.1 or more, with the raw material mixture and thus eliminate an amount of the CaO-containing material separately added into the melting furnace in result, for a smoother melting operation in the melting furnace; and it is further preferable to adjust the feeding amount of the carbonaceous material for hearth material in such a manner that an amount of the carbonaceous material of a non-combustion state fed into the melting furnace together with the solid reduced iron discharged from the reducing furnace becomes not less than an amount of the carbon aqueous material to be consumed in the melting furnace, for further reliable improvement in the metallization ratio of the solid reduced iron obtained in the reducing furnace, and for a more efficient and faster melting operation in the melting furnace.

[0009] It is also preferable to adjust a MgO content in the raw material mixture or to add MgO additionally into the melting furnace in such a manner that the slag generated in the melting furnace has a MgO content of 6 mass % or more, preferably 8 to 13 mass %, for effective suppression of refractory wear in using magnesia bricks as an inner lining refractory for the melting furnace. In this case, it is preferable to adjust a blending amount of CaO— and MgO-containing materials in the raw material mixture in such a manner that an amount of the slag-conditioning agents including CaO and MgO fed additionally into the melting furnace becomes 40 kg or less per ton of the molten iron obtained in the melting furnace.

Problems solved by technology

The direct iron making method using a moving-hearth reducing furnace connected to a melting furnace as described above has been studied for a fairly long period, but there are still many problems to be solved for operation in the industrial scale, for example, in operational stability, safety, cost, product quality (purity of molten iron), etc.

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