The steelmaking industry, producing 1,831.5 million tonnes of crude steel in 2022, generates approximately 40 wt.% of slag, a valuable by-product containing up to 40 wt.% of iron oxides and other metal oxides. This makes steelmaking slag extremely attractive as an alternative to raw materials. To prevent permanent losses of metals to the slag and to promote metal circularity, new sustainable metal recovery methodologies are needed. This research adopts a simulation-driven approach to explore the potential of hydrogen gas (in comparison to carbon) as a reducing agent for iron oxides in Electric Arc Furnace (EAF) steel slag.

Firstly, thermochemical equilibrium calculations were performed using the FactSage 8.3 software to explore multicomponent and heterogeneous slag-metal-reductant (hydrogen or carbon) systems of various iron oxide contents (9 - 39 wt.%) and constant basicity (CaO/SiO₂ ≈ 2.2). The results indicate that hydrogen gas yields iron recovery rates comparable to carbon, particularly in slags with iron oxide contents of ≤ 20 wt.%. However, the use of hydrogen as a reductant shows a more favorable trade-off between the recovered iron purity and the reduction performance.

Secondly, the thermochemical calculations were expanded to incorporate a comprehensive study of the process kinetics using the Effective Equilibrium Reaction Zone (EERZ) approach. The developed kinetic model offers valuable insights into the dynamics of mass, temperature, and composition evolution during the hydrogen-driven reduction of slag.

The results of this study contribute to a deeper understanding of hydrogen-based metallurgical processes, disclosing new avenues for designing less CO2-intensive routes.