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

• Experiments of ammonia-based reduction of industrial iron ore pellets directly illuminated by a concentrated light flux were performed. • Kinetics for ammonia-based reduction is slower than for hydrogen which is attributed to the difference in diffusion rates. • Nonetheless, satisfying reduction yields were reached: more than 95% of reduction were achieved on iron ore pellets after 16 min of exposure. • A further decrease of the reduction time is achieved using flat samples (disks): reduction yield greater than 95% after only 6 min of exposure. Iron and steelmaking are responsible for around 7% of global CO 2 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.