Effective induction of magnetite on suspension magnetization roasting of hematite and reaction kinetics verification

Abstract

Suspension magnetization roasting is an effective method for processing complex refractory iron ores. During industrial production, it was found that the separation index after magnetization roasting could be better optimized than with hematite alone; however, no pertinent study has been reported on the induction mechanism of magnetite during the reduction kinetics of hematite. In this study, the effect of magnetite on the reduction of hematite in the process of suspension magnetization roasting was investigated, and the mechanism of the induction reduction process was revealed by XRD, VSM and isothermal kinetic analyses. The results show that the addition of magnetite increases the conversion degree and reduction rate of hematite, and the magnetic conversion rate increases from 16% to 46% in the presence of 16% magnetite. The XRD and VSM analyses confirm that the addition of magnetite promotes the reduction speed of hematite and enhanced the magnetic properties of the roasting products. Isothermal kinetic analysis reveals that the initial stage of hematite reduction is controlled by the shrinking core model R4, and the final stage is controlled by the three-dimensional diffusion model D6. Compared with pure hematite, the pre-exponential factor and apparent activation energy of the reduction reaction decrease with the addition of 16% magnetite, which indicates the acceleration and promotion of magnetite on the reduction of hematite. This study provides important insights into the efficient and clean reduction of hematite with magnetite.