Integrated Recycling of Red Mud for Iron Ore Sinter Manufacturing: Interfacial Bonding Regulation of the Sintering Process

Recycling of red mud (RM) has posed an enduring challenge for the alumina industry. This work offers a comprehensive investigation into the fundamental and applied research of RM blend into the iron ore sintering process. Microsintering test was employed to investigate the formation and properties of bonding phase affected by RM. It resulted in impairment of bonding phase infiltration onto the iron ore surface and a decrease in the interfacial bonding strength. The interfacial interaction mechanism showed that the excessive TiO₂ and Al₂O₃ brought by RM leads to the transformation of calcium ferrite (the target bonding phase) into perovskite and spinel with high melting points, resulting in the evolution of bonding phase from original dense strip-crystallized structure to fine-grained porous. Incorporation of CaO in conjunction with RM facilitates the formation of calcium ferrite within the bonding phase and enhances its infiltration on the iron ore surface, thereby augmenting interfacial bonding strength. Pilot-scale sintering was successfully conducted with 6% RM and 1.5% quicklime. The sinter yield of 76.68% and a tumbling index of 64.98% can be obtained, which were comparable to those achieved without RM, offering a feasible approach for large-scale recycling of RM in the steel industry.