Doctoral Network on the adoption of Hydrogen mEtalLurgy In the climate-neutral production Of Steel - HELIOS

WP2: Hydrogen-based processes in stainless-steel manufacturing

WP2 is related to research objectives RO2 and RO3. To reach RO2, develop first-of-a-kind hydrogen plasma-based reduction processes for stainless-steel producers and their raw-material producers, we identified two existing commercial processes with high CO2 emissions and for which we expect breakthroughs through the introduction of hydrogen-plasma to replace carbon as reduction agent. Firstly, FeCr is currently produced through the Submerged Arc Furnace (SAF) as raw material for stainless-steel production. To mitigate this source of CO2 emission, DC5 at K1-MET will use state-of-the-art hydrogen-plasma smelting reduction (HPSR) equipment to evaluate the reducibility of Cr2O3. After evaluating a method to characterize the kinetic parameters, DC5 will determine the optimum process conditions, and expand the investigation to mixtures of Cr2O3 with other oxides like Fe2O3, to realize the first H-reduced metallic Fe-Cr suitable for use as raw material in the EAF melting together with scrap. The research work of DC6 at KU Leuven aims to evaluate the use of hydrogen plasma as an alternative reducing agent for the reduction of Cr2O3-containing slag in the Argon Oxygen Decarburisation (AOD) process, to mitigate the CO2 emissions of the production of FeSi which is currently typically used as reducing agent. This study runs in the first part parallel with DC5, for which a secondment at K1-MET is foreseen to work together with DC5 on the reduction of Cr2O3, but for which then the focus is directed to other mixtures relevant to AOD slag. To deliver the proof-of-concept of this highly innovative idea, DC6 will perform lab-scale HPSR experiments at KU Leuven on Cr2O3-containing slag systems, including other oxides like CaO and SiO2. Using advanced characterisation techniques like Electron-Probe Micro Analysis (EPMA), the reduction phenomena and extent will be determined, thereby enabling DC6 to evaluate the suitability of hydrogen plasma as reducing agent in the AOD process.

For RO3, in order to develop metal-recovery processes for residues from steel production based on hydrogen and/or hydrogen plasma reduction, we will demonstrate the applicability of these techniques on complex residues from the stainless steel production, such as flue dusts. The goal is not only to recover the metals, but also develop the methods to separate them. DC7 at the KU Leuven will collect data from industrial process residues to identify the relevant compositions and components for experimental investigation, considering Fe, Zn, Ni, Cr, and possibly Cu and Co, as main elements. Based on thermodynamic calculations, DC7 will design lab-scale experiments with synthetic mixtures to evaluate the reduction efficiency and rate by hydrogen or hydrogen plasma. Suitable processing conditions will be determined to maximize the valorisation potential of the resulting products. This research will be performed in close collaboration with the Recyco division in Aperam Stainless Europe. Through a secondment at TU Delft, the valorisation options will be further explored using hydrometallurgical processes.