Reduction of Molten Iron Oxide and FeO Bearing Slags by H2-Ar Plasma

Abstract

(I) Reduction of molten iron oxide and FeO bearing slag by H2-Ar plasma was studied using water cooled Cu crucible. The sample weights were 25 to 75g, the flow rate of mixture-gas was 20l/mm and DC electric power of plasma was 8.3kW. Results obtained were as follows:(1) The reduction of molten iron oxides proceeds linearly with time and the reaction rate is proportional to the partial pressure of atomic hydrogen. Therefore, it is considered that the rate determining step is the chemical reaction between FeO and the atomic hydrogen formed by thermal dissociation in the plasma.(2) The rate of reduction of FeO bearing slag is lower than that of molten iron oxide and is proportional to the FeO concentration in slag. It is presumed that the reduction rate is controlled by both the chemical reaction rate of FeO with atomic hydrogen at the gas-solid interface and the mass transport rate of FeO across the boundary layer between the interface and the molten slag bulk.(3) The reduction of molten iron oxide and FeO bearing slag by H2-Ar plasma takes place only on the cavity formed at the surface of melt by the momentum of plasma jet gas.(II) Continuous melting of pre-reduced ore powder, obtained by a fluidized bed reduction was examined using MgO crucible and H2-Ar plasma.Following results were obtained:(1) Carry-over loss of the pre-reduced ore powder during the melting in plasma arc furnace was small, when the condition of powder feeding and plasma arc were properly chosen.(2) Reduction of FeO in slag, accompanied in fed material, by H2-Ar plasma, could be described by a simple model of continuous melting and reduction, based on experimental results of the reduction of FeO bearing slag as described (1-2).With this model, the rate of reduction during continuous melting was determined.