The reduction behaviour of hematite compacts by H2‐CO gas mixtures was investigated at 1073‐1223 K. The total porosity, pore size distribution and surface area of the compact was measured using mercury pressure porosimeter. The reduction tests were carried out using Cahn balance. The reduction behaviour could not be described in terms of a single rate‐determining step; the reduction process was initially controlled by the chemical reaction at the oxide/iron interface, controlled by the intraparticle diffusion through the reduced layer towards the end of reduction, and the mixed control, in between. Over the whole range, the reduction rate decreased with CO content in the gas mixture. The chemical reaction rate constants were two to three times higher for H2 reduction than those of CO reduction, and the effective diffusivities of H2 reduction were three to four times higher than those of CO reduction. Values of activation energy for chemical reaction were found to be 19.8‐42.1 kJ/mol depending on the gas compositions; 100% CO showing the lowest.

It is necessary to understand the thermodynamic properties of MnO in steelmaking slags for the smelting reduction of Mn ore in BOF process. Studies of the manganese distribution between CaO-SiO 2 -Fe t O-MnO slags and liquid silver in equilibrium with solid Fe in the temperature range of 1 623 to 1 723 K were carried out under a CO/CO 2 atmosphere.The Fe t O content in (32.4ϳ36.3)%CaO-(31.6ϳ44.0)%SiO 2 -(9.9ϳ24.1)%FeO-(0.4ϳ2.6)%Fe 2 O 3 -(8.9ϳ 10.8)%MnO slags was found to have a linear relationship with oxygen partial pressure. The values of Fe 3ϩ /Fe 2ϩ in the same slag system increase by increasing the Fe t O content. The Mn distribution ratio between slag and metal, (%MnO)/[%Mn] Fe-C sat , increases with FeO content in a linear relationship over the measured FeO concentration range (6.7-24.1 mass%). The Mn distribution ratio decreases with increasing CaF 2 , which is believed to have the effect of increasing the activities of MnO and FeO.Temperature dependence of equilibrium manganese distribution at p O 2 ϭ6.6ϫ10 Ϫ12 atm in the temperature range of 1 623 to 1 723 K can be expressed as follows:The relative partial heat of solution of MnO into (32.7ϳ39.1)%CaO-(32.7ϳ38.8)%SiO 2 -(10.2ϳ20.78)%FeO-(1.0ϳ2.4)%Fe 2 O 3 -(9.4ϳ10.8)%-MnO slags was estimated to be 198 kJ/mol.

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