Article ID: ISIJINT-2021-390
As Sweden transitions to hydrogen-based steel production to enable fossil-free steelmaking, excess oxygen is likely to be generated through hydrogen production via water electrolysis based on green electricity. Further, during iron-ore pellet production, magnetite oxidises to hematite, releasing considerable heat. This excess oxygen and inherent heat can be used to promote exothermic oxidation, reducing the external fuel requirement, decreasing greenhouse gas emissions, and conforming to the Paris climate agreement. In this study, the effects of a high-oxygen-content (40% O2) inflow gas on pellet bed oxidation during induration were investigated, focusing on the resulting temperature profiles in the bed and the strength development of the produced pellets. An interrupted pot furnace experimental methodology was employed on the bed scale, with an approximate scale of 100 kg pellets per bed. The results indicate that the use of 40% O2 gas helps rapidly enhance the pellet properties and yields a more uniform pellet bed in terms of oxidation degree compared to the use of 13% O2 gas. In addition, improved cold compression strength (CCS) can be achieved when using 40% O2 inflow-gas. At temperatures above 1000°C, the oxidation degree and CCS are primarily enhanced by the high oxygen level of the inflow gas; this behaviour cannot be compensated for by increasing the temperature and residence time at a lower oxygen level. The positive effects on the bed-scale oxidation degree and strength are promising and may enable faster production rates in the future.