Study on Direct Reduction of Low-Grade Iron Ore-Coal Mini-pellets in Coal-Based Rotary Kiln

In this work, research of reduction process was studied by means of rotary kiln (φ1.5 m × 15 m) process anatomy in order to provide fine guidance to large-scale operation. It was shown that the average reduction degree of 89.96% and metallization ratio of 85.15% were obtained at the highest temperature of 977 °C and total residence time of 90 min. The generation amount of metallic iron in section of temperature higher than 900 °C and lower than 900 °C was 34.15 and 56.38%, respectively. The section of lower temperature of 830–900 °C played an important role in formation of metallic iron, making it possible for mini-pellet to reduce quickly at lower temperature. Two main tasks were completed for mini-pellets in rotary kiln: the reduction of iron oxides in the range of 15.0–4.5 m as well as migration and beneficiation of metallic iron, facilitating the subsequent separation of iron and gangue minerals.