Re-Oxidation Kinetics of Flash Reduced Iron Particles in O2-N2 Gas Mixtures Relevant to a Novel Flash Ironmaking Process

A novel flash ironmaking process based on hydrogen-containing reduction gases is under development at the University of Utah. This process will directly reduce fine iron oxide concentrate particles in suspension in a flash reactor. During handling and transportation, product iron particles may come into contact with air. Since direct reduced iron is usually prone to oxidation, re-oxidation kinetics is of concern. The goal of this work was to determine the re-oxidation kinetics of flash reduced iron particles in O-2-N-2 gas mixtures. The effects of temperature (673 - 873 K) and O-2 partial pressure (4 - 18 kPa) were studied and the nucleation and growth model was found to describe the initial period of oxidation before the rate decreased precipitously at certain conversion. The pressure dependence of the rate was first order with respect to oxygen partial pressure, and the activation energy was 14.4 kJ/mol. A complete rate equation that adequately represents the experimental data was developed.