Pilot-Scale Application of Red Mud-Based Slag Pellets in Steelmaking: Process Optimization, Mechanism, and Life Cycle Assessment

The resource utilization of red mud (RM) is crucial for the aluminum industry and for addressing environmental concerns. In this study, RM-based slag pellets were prepared through a cold pressing process and used for converter steelmaking. In the pellet preparation experiment, the effects of binder starch and carboxymethyl cellulose sodium (CMC) dosage, moisture content, drying temperature, particle size, and forming pressure on the strength of RM-based pellets were studied. The formation mechanism of RM particles was determined by analyzing the changes in the crystal structure, functional groups, elemental valence state information, and density functional theory calculations. Finally, the environmental benefits of the pellet production process were analyzed. Under the optimal reaction conditions, the compressive strength of RM pellets prepared based on starch and CMC can reach 1162.06 and 1345.6 N/P, which can meet the production needs of the converter. Mechanism analysis shows that organic adhesives adsorb and solidify particles through chemical or hydrogen bonding, resulting in a denser particle structure. RM particles have an excellent slag and phosphorus removal performance. The results of the life cycle assessment clarify the potential contributions of each stage of particle production. The raw materials and transportation distance have significant impacts on the particle production system. The experimental results provide theoretical guidance and a sustainable evaluation for the production of RM slag aggregates.