Solid state carbothermic reduction of manganese ores

Characteristics of carbothermic reduction of manganese ores have been studied by classical thermogravimetric technique in the temperature range between 1100°C and 1350°C. Reaction products have been investigated by X–ray diffraction, scanning electron microscopy, energy dispersive analysis and image analysis. The effects of particle size and different gas atmospheres have also been studied. On the basis of the findings, a two–stage mechanism has been proposed. The first stage includes the reduction of higher oxides to their lower stages by carbon and carbon monoxide. During this rapid initial stage products were porous to varying degrees. In this stage rate control appears to be mixed: both inward diffusion of carbon monoxide and outward diffusion of carbon dioxide and the reaction of carbon monoxide on the pore walls of oxide phase play very important roles. During the second stage, the reaction is limited to the interface between manganous oxide and mixed carbide of iron and manganese. The chemical reaction between the oxide and carbon appears to be the rate controlling mechanism.