As a typical refractory iron ore, the utilization of limonite ore with conventional mineral processing methods has great limitations. In this study, suspension magnetization roasting technology was developed and utilized to recover limonite ore. The influences of roasting temperature, roasting time, and reducing gas concentration on the magnetization roasting process were investigated. The optimal roasting conditions were determined to be a roasting temperature of 480 °C, a roasting time of 12.5 min, and a reducing gas concentration of 20%. Under optimal conditions, an iron concentrate grade of 60.12% and iron recovery of 91.96% was obtained. The phase transformation, magnetism variation, and microstructure evolution behavior were systematically analyzed by X-ray diffraction, vibrating sample magnetometer, and scanning electron microscope. The results indicated that hematite and goethite were eventually transformed into magnetite during the magnetization roasting process. Moreover, the magnetism of roasted products significantly improved due to the formation of ferrimagnetic magnetite in magnetization roasting. This study has implications for the utilization of limonite ore using suspension magnetization roasting technology.

In this study, a novel technology for the comprehensive utilization of low-grade iron ore is presented. For the iron ore with a Fe content of 24.91%, a pilot-scale study of pre-concentration, suspension magnetization roasting, grinding, and low-intensity magnetic separation was conducted, and an iron concentrate with a grade of 62.21% and a recovery of 85.72% was obtained. The products were analysed using chemical elemental analysis, particle size analysis, X-ray diffraction, scanning electron microscopy, and vibrating sample magnetometry. The results indicated that hematite was reduced by CO and H₂ mixture and transformed into ferrimagnetic magnetite in the suspension magnetization roasting, which was easily recovered in the subsequent magnetic separation. Additionally, a pre-concentration tailing with a SiO₂ content of 81.55% and a magnetic tailing of the roasted ore with a SiO₂ content of 79.57% were obtained, which can be used as building materials. This presents significant implications for the comprehensive utilization of low-grade iron ore.

This study presents a fluidization roasting technology for siderite-bearing iron ore without the use of carbon additives. Samples of Jingtieshan iron ore were subjected to fluidization magnetization roasting, and the effects of roasting temperature, time, and N₂ flow rate on the magnetic separation performance were explored. An iron concentrate with an iron grade of 57.40% and recovery of 91.17% was acquired at a roasting temperature of 700 °C, roasting time of 10.0 min, an N₂ flow rate of 600 mL/min, grinding particle size of −125 μm, and constant magnetic intensity of 99.47 kA/m. The samples were characterized by X-ray diffraction, optical microscopy, scanning electron microscopy–energy dispersive spectroscopy, and vibrating sample magnetometry. The results revealed that hematite and goethite were reduced to magnetite by the CO generated during siderite decomposition; meanwhile, siderite was transformed into magnetite with the consumption of CO during the reduction process. The saturation magnetization of the roasted ore significantly increased owing to the formation of ferrimagnetic magnetite, which was easily recovered in the subsequent magnetic separation.

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