Impact of Reduction Conditions on Metallic Fe Growth Mechanism of Australian Ores in H2-Fluidized Bed

The hydrogen-fluidized bed-based technology is a prospective pathway for direct reduced iron (DRI) production. Australia has the world’s largest economic resource of iron ores, which is mainly used in the traditional blast furnace process. The suitability of Australian hematite–goethite ores in hydrogen fluidized bed reduction needs to be assessed. Therefore, low-grade Australian hematite–goethite ores were tested in this study, aiming to investigate the fluidization reduction behavior under various operational conditions and to understand its impact on fresh metallic iron formation. Operational temperatures were tested from 650 to 950 °C and H2 concentrations were set as 70 and 90% mixed with N2 gas. The reduction degree was calculated based on analysis of off-gas using a micro-GC. The morphology change of directly reduced iron samples with different conditions was evaluated by Scanning Electron Microscope and surface area analyzer. These results showed that with the increase of temperatures and H2 concentration, densely layered metallic Fe is more prone to form during the reduction, which will further hinder the permeability of H2 and retard the reduction process. The reduction condition plays a key role in the morphology evolution which is decisive in determining reduction performance and sticking occurrence. This work demonstrated the significance of controlling reduction conditions in optimizing the reduction behavior and the potential of using Australian hematite–goethite ores in hydrogen DRI processes.