Enhancing Oxidation and Energy Utilisation by Controlling O<sub>2</sub> and Gas Flow in Magnetite Pellet-Bed Induration

As Sweden transitions to hydrogen-based steel production, excess O2 generated as a byproduct of H2 production through water electrolysis is likely to be available. This presents an opportunity to use extra O2 for reducing fuel consumption during production of iron ore pellets. Considerable heat is released as magnetite is oxidised to hematite during induration. Increased O2 content in the process gas is expected to accelerate the exothermic oxidation reaction, allowing faster intrinsic heating of the bed. This study examines various energy scenarios utilising O2-enriched gas (40 vol% O2) relative to a base case that uses low-O2 gas (13 vol% O2). The focus is the effects of the flow rates and O2 contents in the inflow gas on the temperature development and physicochemical properties (oxidation degree and cold compression strength) of pellets across a 100-kg pot furnace bed. Enriching the inflow gas with O2 has advantages with regard to the aforementioned properties. Notably, utilising O2-enriched gas at a reduced flow rate (in this case, 30% less gas volume compared with the base case) enables improved heat distribution relative to the base case with low-O2 gas. In addition to the effects on the energy and pellet properties, the microstructures are analysed with respect to the underlying oxidation mechanisms.