The present invention relates to the melt reduction of iron oxides. This practice fundamentally involves feeding iron oxides, possibly in the form of iron ore, mixed with carbonaceous material, such as coke particles, to an iron melt where the carbon reacts with the oxides so that the iron is added to the melt, the reaction gases being discharged from the enclosure of the furnace containing the iron melt.
When practiced conventionally by the use of a direct current electric arc furnace, with the arcing electrode cathodic and the melt anodic, the materials, normally intermixed, must be of a relatively large particle size to prevent them from being blown about by the gases evolving from the melt and by action of the arc, so as to be lost by being carried away via discharged reaction gases. It is desirable to have the reducing reaction proceed as rapidly as possible, this suggesting that the particles of the materials be reduced to a fine grained condition, such as in the form of powder.
The use of a direct current arc formed between a cathodic arcing electrode and an anodic iron melt, is advantageous because the action of the arc displaces slag floating on the melt, to form a bare spot of iron free from slag, the presence of slag interfering with the desired reaction.
U.S. Pat. No. 3,940,551, dated Feb. 24, 1976, discloses the use of a tubular arcing electrode operated as a cathode, the melt being the anode, this permitting very fine-grained iron oxide material and carbonaceous material to be fed directly into the arc of a DC arc furnace, the arc action displacing any slag to form a spot of bare iron, to which the powdered materials are fed directly, the magnet and electrical forces of the arc having the effect of confining the flow of powdered materials.
However, the above patented invention has the disadvantage that the refractory lining of any furnace used, is directly exposed to the arc flare with attendant danger of early lining deterioration. The constantly fed flow of fine-grained or powdered materials is to the inside of the arc electrode having the vertical feeding passage or hole; the feed materials can have no shading or shielding action with respect to the arc flare.