Fluidized magnetization roasting of refractory siderite-containing iron ore via preoxidation–low-temperature reduction

Magnetization roasting is one of the most effective way of utilizing low-grade refractory iron ore. However, the reduction roasting of siderite (FeCO₃) generates weakly magnetic wüstite, thus reducing iron recovery via weak magnetic separation. We systematically studied and proposed the fluidized preoxidation–low-temperature reduction magnetization roasting process for siderite. We found that the maghemite generated during the air oxidation roasting of siderite would be further reduced into wüstite at 500 and 550°C due to the unstable intermediate product magnetite (Fe₃O₄). Stable magnetite can be obtained through maghemite reduction only at low temperature. The optimal fluidized magnetization roasting parameters included preoxidation at 610°C for 2.5 min, followed by reduction at 450°C for 5 min. For roasted ore, weak magnetic separation yielded an iron ore concentrate grade of 62.0wt% and an iron recovery rate of 88.36%. Compared with that of conventional direct reduction magnetization roasting, the iron recovery rate of weak magnetic separation had greatly improved by 34.33%. The proposed fluidized preoxidation–low-temperature reduction magnetization roasting process can realize the efficient magnetization roasting utilization of low-grade refractory siderite-containing iron ore without wüstite generation and is unlimited by the proportion of siderite and hematite in iron ore.