Effects of NaOH Content on the Reduction Kinetics of Hematite by Using Suspension Magnetization Roasting Technology

Abstract

Red mud is a potential iron resource that needs to be urgently exploited and utilized. However, due to the properties of high alkalinity, fine particle size and complex mineral composition, the utilization of red mud is difficult. Focusing on red mud’s prominent feature of high alkalinity, this paper studies the influence of NaOH content on the reduction kinetics of hematite, which is the main component of red mud. The results show that the conversion degree of hematite was strongly inhibited by NaOH, and the magnetization and specific magnetic susceptibility of reduction products was significantly decreased with the increase in NaOH content. Meanwhile, the results of the calculation of kinetics parameters demonstrate that the addition of NaOH did not affect the control step of the reduction of hematite, while it dramatically decreased the reduction rate of hematite. Moreover, thermodynamic analysis and SEM-EDS detection were conducted to uncover the inhibited mechanism of NaOH on the reduction of hematite, which indicated that sodium ferrite could be produced spontaneously under the experimental conditions and that it is hard for it to be further reduced by CO. Furthermore, the produced sodium ferrite formed a dense film, which covered the surface of the hematite particles, inhibiting the diffusion of CO and thereby hindering the reduction of the interior hematite.