Mechanistic elucidation of multi-stage reduction dynamics in biomass-driven iron-rich red mud systems

抄録

A direct reduction iron technology, using red mud as raw material and biomass as reducing agent has been proposed to address the massive accumulation of red mud. The reduction behavior and kinetics of pellets under various reaction conditions are investigated. The results indicate that as the reaction temperature increases to 1373 K and the reduction time increases to 60 min, metallic iron gradually increases, while hematite and wustite gradually decrease, both of which improve the porosity and surface area of the pellets, thereby enhancing reduction rate. As the reaction are further increased, the liquid fayalite blocks the pores of pellets, the reduction rate of pellets tends to level off. Kinetic analysis suggests that the reduction reaction is respectively controlled by chemical reactions, gas diffusion, and external gas diffusion during 0-3 min, 30-60 min, and 60-120 min, and the increase in activation energy limits the iron reduction process. Consequently, the most economical reduction conditions for the pellets under current experimental conditions are a reduction time of 60 min at a reduction temperature of 1373 K. The proposed iron ore reduction process is expected to directly use biomass for iron reduction with high efficiency and significant environmental benefits.