Thermal analysis and isothermal reduction kinetics of alkaline hematite in an advanced suspension roaster

Abstract

The reduction kinetics of hematite in alkaline environment has not been studied. In this paper, the possible chemical reactions in the process of iron extraction from red mud by suspension magnetization roasting were systematically calculated and analyzed, and the isothermal kinetic analysis of reduction reaction of the Na2O-Fe2O3-CO system was investigated. The results showed that Fe3O4 would be over-reduced to FeO or Fe easily if the CO concentration was high. The best kinetics model for Na2O-Fe2O3-CO system was the D6 model, the corresponding mechanism function was F(α) = [1− (1 − α)1/3]2 = kt, the pre-exponential factor (A) was 639051.29 min−1, the apparent activation energy (Eα) was 122.05 kJ/mol. The diffusion of CO in hematite was the restrictive step, and the addition of sodium carbonate hindered the reduction process of hematite. This research provides an important insight into the efficient and clean reduction of hematite in red mud.