Towards solar metallurgy: Iron ore reduction by ammonia under concentrated light flux

Abstract

Iron and steelmaking are responsible for around 7% of global CO₂ emissions. The use of fossil fuels to provide both the heat needed to reduce iron ore into iron and the reducing agent is the principal cause of these emissions. Here, we focus on an alternative pathway for direct iron ore reduction using concentrated light power as the heat source and ammonia as the reducing gas. Experiments were performed on industrial iron ore pellets and compared to the ones obtained using hydrogen as a reducer. We showed that below 600 °C, reduction with ammonia proceeds via iron nitrides formation. Reduction dynamics is slower for ammonia for short exposure times but is rapidly caught up, so that reduction ratios as high as the ones obtained for hydrogen are observed. Notably, degrees of reduction exceeding 90% in 5 min were obtained on disks cut from industrial iron ore pellets. This work therefore opens a promising route towards ammonia-based solar metallurgy.