Reaction Mechanism of In-situ Carbon in Hematite Ore Pellet during Induration

Carbon is used in the hematite ore pellet as a partial heat source for induration. Apart from this, it has several other roles in the pellet. To achieve the maximum benefit of carbon in pellet quality improvement and energy reduction, a detailed study on the mechanism of C reaction in hematite pellets is required. Although some investigators have reported improvement in pellet properties on using carbon, its detailed analysis is still lacking. For this, the study on the reaction mechanism during induration is essential, which has not been done so far. To alleviate the above knowledge gap, the reaction mechanism of in-situ carbon has been studied through thermodynamic analysis and experimentation in this work. The possibility of evolving carbon monoxide and carbon dioxide during the burning of carbon at the initial stage has been analyzed from the thermodynamic study. The produced carbon monoxide gas may partially reduce the iron oxides in the pellet. This in-situ reduced iron oxide may be beneficial in the sintering of pellets. The possibility of reduction of ferric oxide in pellets followed by its re-oxidation in the final stage has been studied thermodynamically and experimentally. This study helps to understand the mechanism of in-situ carbon reaction during induration and its role in improving the quality of pellets and reducing energy consumption. It is found that the use of carbon enhances diffusion bonding in acidic pellets and both diffusion and slag bonding in basic pellets. The use of 1.5% carbon reduces the induration temperature by 50 K.