Study on the kinetics of gas-solid based synergistic reduction of limonite carbon-containing pellets

Abstract

The gas-solid-based synergistic reduction of pellets is an innovative and effective method for iron ore smelting. With the development and utilization of iron resources, ore reserves have been greatly depleted; therefore, as a scarce mineral resource, the comprehensive utilization of limonite has become increasingly important. To study the reduction kinetics of pellets in depth, this study used coke and reducing gases (CO and H2) to study the reduction characteristics and changes occurring in carbon-containing limonite pellets. The results showed that the total weight loss percentage of pellets gradually increased with the temperature. The C/O molar ratio had a greater effect on the total weight loss percentage of pellets in a N2 atmosphere, but it had no significant effect in CO or H2 atmospheres. The maximum reaction rate increased with increasing temperature. The reduction reaction was the most difficult to proceed in the N2 atmosphere, and the reaction was most likely to occur in the CO atmosphere. The analysis of pellets by EPMA and XRD found that the pellets reduced in the N2 atmosphere had the lowest porosity, and the pellets reduced in the H2 atmosphere had the highest porosity, which was more conducive to gas diffusion. Some of the unreduced Si, Al, Mn, Ca, and Fe in the pellets reduced in the N2 atmosphere precipitated in the form of oxides, but when a reducing gas (CO, H2) was introduced, precipitation did not occur.