Mechanism of iron grains aggregation and growth in metalized pellet under the alternating magnetic fields

Abstract

The direct reduction-magnetic separation method is highly efficient for producing metallic iron powder from low-grade complex ore resources. However, the limitation lies in the small average size of iron grains, which impedes the subsequent separation between metallic iron and gangue minerals. To address this, a novel method utilizing induction heating was introduced to stimulate the aggregation and growth of iron grains. Our study systematically investigated the growth kinetics behavior of iron grains under alternating magnetic fields. Additionally, we compared the impact of induction heating versus conventional heating on iron grain growth and delved into the mechanism through which the magnetic effect enhances the aggregation and migration of iron grains. The results indicate that iron grains can effectively aggregate and migrate to the edges of cracks or pellet surface under alternating magnetic fields, realizing the increase of average iron grain size and the pre-separation of metallic iron from gangue minerals. Specifically, the average iron grain size increased from 12.95 μm to 36.58 μm when induction heating temperature at 1300 °C for 100 min. Additionally, the total iron grade of concentrate reached 94.60% with ball milling 30 min and magnetic field intensity of 750 Gs. Finally, the growth model of iron grains under alternating magnetic fields was established and the mechanism of magnetic effect on promoting iron grains growth was revealed.

Keywords

• Induction heating
• Iron grain growth
• Granularity characteristic
• Growth kinetics
• Magnetic effect