Sustainable Ironmaking Toward a Future Circular Steel Economy: Exploiting a Critical Oxygen Concentration for Metallurgical Cu Removal from Scrap-Based Melts

Abstract

A circular steel economy based on recycling scrap is severely hampered by the increasing accumulation of Cu returning from more and more electrified products, which severely limits processing, application, and safety of steels. As of yet, no viable strategies for its removal have been developed, and the increasing Cu contamination can only be diluted with fresh primary iron. This is not only evoking CO2 emissions from conventional reduction processes, but also merely delays the problem until global demands allow for a circular steel economy. However, the ongoing transformation toward green steel making may offer pathways to overcome this complex metallurgical challenge. It is demonstrated that Cu can be effectively evaporated from Fe–Cu–O melts—representing Fe ore mixed with Cu-contaminated steel scrap—during hydrogen plasma-based smelting reduction. This evaporation is found to be strongly influenced by the Cu activity determined by the concentration of oxygen in the liquid, with a critical O concentration of about 22 wt%. Even without the presence of hydrogen, Cu concentrations can thereby be drastically reduced from 1 to less than 0.1 wt%. Potentials and challenges for leveraging these fundamental findings on a laboratory scale for future industrial production of green steel are outlined and discussed.