Kinetics and Mechanism of Reduction of Iron Ore-Coal Composite Pellets and Its Usage in Smelting Reduction Process

Enormous amount of fines are generated in Indian iron ore and coal mines due to mechanized mining and mineral dressing operations. Utilization of these fines for extracting metal is of vital concern for judicious resource utilization and pollution control. The term composite pellet is being employed here to mean a pellet containing mixture of fines of iron bearing oxides and carbonaceous materials (coal/coke/char), which has been imparted sufficient green strength for subsequent handling by cold bonding technique. The reduction kinetics, in iron ore-coal composite pellet, is expected to be enhanced due to the presence of reductant in-situ which causes shortening of diffusion distances of reductant and availability of large number of reaction sites. The reduction kinetics in iron ore-coal composite pellets is very complex with respect to simultaneous reaction steps in a system consisting of solid and gas phases. The movements of reactants and products at the interface are affected by several factors which control the rate of reduction. In iron ore reduction, majority of actual systems involve non-isothermal conditions. The physical properties of the composite pellets have also been evaluated. Composite pellet based alternative ironmaking processes constitute a promising route for ironmaking in future and therefore, a clear understanding of kinetics and mechanism of reduction in composite pellets is extremely important. This paper presents the kinetics and mechanism of reduction of iron oxides in composite pellets under non-isothermal conditions and their usage in smelting reduction processes