Process Intensification and Comparison of Electrolytic Hydrogen Green Steel Plants for Industrial Decarbonization

Abstract

There is a growing interest to produce steel by using a direct reduced iron shaft furnace that reduces iron ore using electrolytic produced hydrogen, followed by an electric arc furnace. This method, called the H₂-DRI-EAF steel production pathway is currently being implemented at full-scale with several different designs available and can help play a major role in industrial decarbonization. In this work, three main designs are investigated: the SOE-R Design – a novel design that utilizes solid oxide electrolyzers (SOEs) and recycles steam to keep process temperatures high, the SOE-NR Design – a design that utilizes SOEs without recycling steam, and the PEM/AEL Design – a design that uses proton exchange membrane (PEM) or alkaline liquid electrolysis (AEL) electrolyzers. Also investigated is the use of electric arc furnace off-gases to be combusted to supply process heat prior to the direct reduction iron shaft furnace which is compared through the base (B) and off-gas utilization (OGU) sub-designs. Results show that the SOE-R-B Design can produce steel using 3.56 MWh/tonnes liquid steel, representing a 26.9% and 16.6% reduction of energy compared to the PEM/AEL-B Design and SOE-NR-B Design, respectively. Additionally, the SOE-R-B Design produces 1.20 tonnes CO₂e/tonnes liquid steel using E.U. grid electricity, which is lower than current conventional steel pathways. If low carbon grid electricity is used, the SOE-R-OGU Design can produce steel emitting 0.48 tonnes CO₂e/tonnes liquid steel. 83% or more of water can be reduced in the SOE-R Design compared to the SOE-NR and PEM/AEL Designs due to not using any water for cooling to condense steam. Lastly, 23.8% – 42.1% of the natural gas used for process heating in a process heating combustion furnace can be reduced when electric arc furnace off-gas is utilized. Overall, a detailed energy, carbon emissions, and water use comparison of three realistic, full-scale electrolytic hydrogen steel plants is presented.