Hydrogen-Based Direct Reduction of Iron Oxides: A Review on the Influence of Impurities

Greenhouse gas emissions are the primary root cause of anthropogenic climate change. The heterogeneity of industrial operations and the use of carbonaceous fossil fuels as raw materials makes it challenging to find effective solutions for reducing these emissions. The iron and steel industry is responsible for approximately 35% of all industrial CO2 emissions. This value is equivalent to 7–9% of the global CO2 emissions from all sectors. Using hydrogen (H2) as the alternative reducing agent has the potential for a significant reduction in CO2 emissions. Despite decades of research on H2-based reduction reactions, the reaction kinetics are still not well understood. One of the key influencing parameters on reduction kinetics is the effects of impurities in the iron ore, which needs to be unraveled for a better understanding of the reduction mechanisms. The present review paper aims to explore the single and combined effects of common impurities on the reduction behavior as well as the structural evolution of iron oxides.