Improved iron recovery from low-grade iron ore by efficient suspension magnetization roasting and magnetic separation

Considering the decreasing reserves of high-grade iron ores, the utilization of low-grade iron ores is of great significance to the steel industry; however, improving iron recovery from low-grade iron ores is challenging. In this study, to improve iron recovery from low-grade iron ores, preconcentration was performed, followed by two separation processes, namely, reverse flotation (RF) and suspension magnetization roasting-magnetic separation (SRM), which were selected for comparing their effects on Fe grade and Fe recovery. The results showed that the iron grade and iron recovery rate of the concentrate obtained under the optimized RF conditions were 64.76% and 64.83%, respectively, and those under the optimized SRM conditions (500 degrees C roasting temperature, 20 min roasting time, 20% CO concentration, and 200 mL/min gas flow rate) were 69.60% and 99.18%, respectively. The analysis of the roasted products obtained by suspension magnetization roasting through X-ray diffraction, Mossbauer spectroscopy, and X-ray photoelectron spectroscopy and by using a vibrating sample magnetometer showed that most hematite in the roasting feed was reduced to magnetite, which significantly enhanced the saturation magnetization of the roasted product and effectively facilitated the subsequent magnetic separation. Multiple cracks were formed in the roasted product, unlike the roasting feed (which had a smooth surface); the crack formation resulted in the acceleration of the magnetization reaction in the iron ore.