Iron Preparation through Co−reduction Roasting and Magnetic Separation of Iron−rich Red Mud and High Phosphorus Iron Ore

In response to the difficulties in dephosphorization of high phosphorus iron ore and the pollution caused by the storage of iron−rich red mud, this study proposed their co−reduction roasting and magnetic separation. The aim was to replace traditional dephosphorization agents partly with iron−rich red mud and recover iron resources from high phosphorus iron ore and iron−rich red mud synchronously. The effects of red mud proportions, calcium carbonate dosages (collaborative dephosphorization) dosages, and secondary−grinding on iron extraction and dephosphorization were systematically investigated. Combined with HSC thermodynamic calculations, XRD, and SEM−EDS characterization, the mineral transformation mechanisms during co−reduction were revealed. Experiments have shown that when the proportion of iron−rich red mud is 25%, the dosage of calcium carbonate is 6%, the reduction temperature is 1 200 ℃ for 60min followed by two stages of grinding and magnetic separation, a direct reduced iron product obtained contains 85.55% iron (Fe) and 0.250% phosphorus (P). The corresponding comprehensive iron recovery rate is 80.75%. At the reduction temperature of 1 200 ℃, fluorapatite is decomposed and reduced to produce P₂, which reacts with metallic iron and enters the metallic iron phase. When iron−rich red mud is co−reduced with high phosphorus iron ore, its alkaline components (CaO/Na₂O) preferentially combine with SiO₂ and Al₂O₃ in the roasting system, which inhibit the decomposition and reduction reactions of fluorapatite to some extent. In addition, it is necessary to use calcium carbonate in conjunction with iron−rich red mud to enhance dephosphorization. CaO produced by its decomposition can preferentially combine with SiO₂ and Al₂O₃ in the calcination system, further inhibiting the decomposition and reduction reactions of fluorapatite. This study develops a collaborative processing technology based on solid waste, promoting clean utilization of refractory iron ore resources and the large consumption of red mud.