The Mechanism of the Reduction of Hematite-Magnetite Concentrate by Graphite-Calcium Carbonate Mixture in Hoganas Process

In this study, the mechanism of reduction of hematite-magnetite concentrate (HMC) by graphite-calcium carbonate reductant mixture at 1000 °C was investigated. The initial and middle stages of the reduction process (up to 63%) are mainly affected by the heat transfer inside the crucible. In the middle and final stages of the reduction process, the gaseous diffusion to the FeO-Fe reaction interface and the carbon gasification by CO2 jointly controlled this progress. The reduction rate was relatively slow below the temperature at which the carbon gasification by CO2 commences. According to the XRD analysis, prior to the carbon gasification, the metallic iron was not found. The reduction of the HMC hollow cylinder proceeded topochemically mainly from the outer surface. The SEM micrographs indicated the formation of sintered iron whisker.