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 wustite, 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 wustite at 500 and 550 degrees 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 degrees C for 2.5 min, followed by reduction at 450 degrees 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 wustite generation and is unlimited by the proportion of siderite and hematite in iron ore.

Automated summary

This study proposes a fluidized preoxidation-low-temperature reduction magnetization roasting process for the utilization of low-grade refractory siderite-containing iron ore. Through experiments, it was found that the γ-Fe2O3 generated during air oxidation roasting would further convert into weakly magnetic FeO. Stable magnetite can only be obtained through reduction of γ-Fe2O3 at low temperatures. The optimal process parameters for fluidized magnetization roasting were determined to be preoxidation at 610°C for 2.5 min, followed by reduction at 450°C for 5 min. The iron ore concentrate obtained through weak magnetic separation had a grade of 62.0wt% and an iron recovery rate of 88.36%. Compared to conventional direct reduction magnetization roasting, the weak magnetic separation greatly improved the iron recovery by 34.33%. The proposed roasting process enables efficient utilization of low-grade refractory siderite-containing iron ore without wustite generation, and it is not limited by the proportion of siderite and hematite in the ore.