Beneficiation of an iron ore fines by magnetization roasting and magnetic separation

The utilization of abundant low-grade iron ores is potentially important to many countries in the word, especially to China. These iron ores contain many detrimental impurities and are difficult to upgrade to make suitable concentrates for the blast furnace. In this paper, the beneficiation of a low-grade hematite ore fines containing carbonates with magnetization roasting and magnetic separation was proposed and studied. The hematite and siderite are almost completely converted into magnetite by 8 wt% coal at roasting temperature of 800 °C for 8 min. Under the optimized conditions, a high grade magnetic concentrate containing 65.4 wt% iron with an iron recovery of 92.7% was achieved. Meanwhile, the effects of roasting temperature, reaction time and coal to ore ratio on the magnetic properties of roasted materials were investigated using a vibration sample magnetometer (VSM). The results show that the magnetic susceptibility and magnetism saturation of hematite ore can be highly increased due to the selective conversion of hematite and siderite into magnetite caused by magnetization roasting which facilitates their separation from non-magnetic minerals.