Thermodynamic-kinetic modeling of hematite reduction in a laboratory-scale hydrogen plasma smelting reduction furnace

• A dynamic kinetic model for hydrogen plasma smelting reduction (HPSR) is proposed. • Model predicts hematite → magnetite → wüstite → iron reduction sequence for HPSR. • The thermodynamic-kinetic framework couples metal-slag mass transfer under plasma conditions. • The model is validated with data collected from the lab-scale experiments. Reducing CO 2 emissions in ironmaking is a critical challenge for sustainable steel production. Hydrogen plasma smelting reduction (HPSR) has emerged as a promising alternative technology, offering the potential to simultaneously smelt and reduce iron ores without carbon-based reductants. Due to the complex kinetics, plasma composition and high-temperature interactions between plasma species, molten metal, and slag, no mathematical descriptions for the course of the process have yet been proposed thus far. To fill this knowledge gap, a dynamic kinetic model was developed and validated for simulating the reduction of both pure and fluxed hematite in an arc melting furnace under a reducing Ar-H 2 atmosphere (90 vol% Ar–10 vol% H 2 , 1 atm, 5 L/min; 200 A, 10 mm arc length; 12.5 min reduction cycles). Plasma equilibrium composition is precalculated by Gibbs energy minimization and used as a boundary condition at the plasma–melt interface. Based on a modified effective equilibrium constant method, the model couples mass balances with reduction kinetics that are limited by mass transfer and driven by the thermodynamic equilibrium driving force. The model accounts for the oxidation and reduction reactions involving multiple oxidation states of iron under plasma conditions. Comparison with the experimental data (metal/slag masses and XRF) indicates that the model can accurately predict the evolution of the chemical composition of the metal and oxide phases. The predicted dynamics of the transformation pathway hematite → magnetite → wüstite → iron are in good accordance with the X-ray diffraction (XRD) results for the different phases and oxidation states.