Kinetics of hematite to magnetite transformation by gaseous reduction at low concentration of carbon monoxide

Hematite-containing material is accumulated during exploitation and beneficiation of magnetite ore, thus forming tailings and other industrial wastes. Hence, processing the low-grade hematite ore becomes extremely important for the metallurgical industry. The transformation of weakly magnetic hematite into magnetite can enhance the efficiency of magnetic separation. In this work, chemical reduction of hematite to magnetite in an atmosphere with different gas composition was investigated. Gasification of charcoal in the flow of both air and carbon dioxide led to the formation of carbon monoxide. The output gas containing carbon monoxide was found to be an effective reductant for the transformation of hematite into magnetite. Even 5% of CO was sufficient to convert hematite into magnetite, which resulted in an increase in magnetization up to 85 Am-2/kg. The kinetic analysis indicated that the reduction of hematite to magnetite is a single-step process, which can be described using the first-order reaction model. (C) 2019 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.