Investigation of Magnetite Oxidation Kinetics at the Particle Scale

• Published in: Metallurgical and materials transactions. B, Process metallurgy and materials processing science Vol. 50; no. 1; pp. 150 - 161
• Main Authors: Sandeep Kumar, T. K., Viswanathan, N. N., Ahmed, H., Dahlin, A., Andersson, C., Bjorkman, B.
• Format: Journal Article
• Language: English
• Published: New York Springer US 15.02.2019; Springer Nature B.V
• Subjects: Avrami Mechanism; Characterization and Evaluation of Materials; Chemistry and Materials Science; HEAT TRANSFER; MAGNETITE; Magnetite particle oxidation; MATERIALS SCIENCE; Metallic Materials; MICROSTRUCTURE; Nanotechnology; Organic chemistry; OXIDATION; Oxidation Kinetics; OXYGEN; Oxygen content; PARTICLE SIZE; PELLETS; Process Metallurgy; Processmetallurgi; REACTION KINETICS; Shrinking Core Mechanism; SINTERING; Structural Materials; Superposition (mathematics); Surfaces and Interfaces; Thin Films; Magnetite Pellets; Pellet Scale; Oxidation Behavior; Isothermal Oxidation; Avrami Kinetic Model (AKM)
• ISSN: 1073-5615; 1543-1916; 1543-1916
• DOI: 10.1007/s11663-018-1459-5

The induration of magnetite pellets is a complex physico-chemical process that involves oxidation, sintering, and heat transfer. The thermal- and gas-composition profile that is experienced by the pellet in an induration reactor could result in the formation of a homogenous or heterogeneous pellet structure, which could affect the pellet quality. The oxidation kinetics of magnetite pellets from sintering studies have been studied at two levels, namely, the pellet scale and at the particle scale, and the findings of the latter are presented here. The rate of oxidation of the magnetite concentrate depends primarily on temperature, oxygen content in the oxidizing gas, and particle size. These factors are investigated in this study. It was found that the oxidation of the magnetite concentrate is comprised of two distinct stages, a primary stage with high rates followed by a secondary stage where rates decrease significantly. The isothermal oxidation behavior as analyzed by the Avrami kinetic model was found to fit better than the shrinking-core model. The partially oxidized particles were examined microstructurally to supplement the experimental and model results. The Avrami kinetic model for isothermal oxidation was extended to non-isothermal profiles using the superposition principle, and the model was validated experimentally.