High-temperature electrolysis for industrial decarbonisation: a real-scale demonstration in the steel sector

Abstract The decarbonisation of energy-intensive industries is a crucial step towards achieving climate neutrality. Among these, the steel sector remains one of the largest CO 2 emitters, requiring innovative solutions to reduce fossil fuel dependency while maintaining efficiency and product quality. This study gives an overview and presents objectives and early progresses of SYRIUS project (SOEC hydrogen integration and circular use in steelmaking process), a Horizon Europe Innovation Action supported by the Clean Hydrogen Partnership. The main goal of SYRIUS is to integrate a 4.2 MW el Solid Oxide Electrolyser (SOEC) into the process line of an operational electric arc furnace (EAF) steel plant, enabling on-site hydrogen production with waste heat recovery and circular integration of process by-products. The proposed system addresses key technological challenges in hydrogen production and utilization for industrial applications. The SOEC electrolyser, operating at high temperature with high electrical efficiency (speci ic consumption below 37 kWh el /kg H2 ), utilizes steam recovered from the steel reheating process, signi icantly reducing electricity demand compared to low-temperature electrolysis technologies. This approach not only lowers operational costs but also optimises energy use within the steelwork, demonstrating a cost-effective and scalable hydrogen production model. Hydrogen produced on-site will be directly fed into a high-efficiency, fuel- lexible slab reheating furnace, designed for progressive decarbonisation through hydrogen combustion. The furnace can operate with variable H 2 -natural gas mixtures, reducing CO 2 emissions by 5,600 tonnes per year during the project and up to 35,700 tonnes per year with future expansion. Additionally, the oxygen by-product from electrolysis is recovered and reintegrated into the process, further optimizing combustion efficiency and contributing to additional fuel savings. A full-scale demonstration in operational environment of this system will be conducted over 5,000 operational hours, validating the feasibility of integrating the SOEC technology within a complex industrial environment. The study also includes techno-economic assessments to evaluate the potential for cost reductions in hydrogen production, as well as life cycle and sustainability analyses to quantify environmental bene its. This paper addresses advancements achieved in the first months of the project on (i) de inition of system modelling and preliminary process simulation, ensuring that the integration of the SOEC is optimized for efficiency and performance, (ii) engineering and permitting activities to establish the necessary regulatory framework for installation, (iii) early-stage SOEC stack development, focusing on material validation and component design, and (iv) waste heat recovery strategies, exploring how steam from the reheating furnace can be efficiently redirected to support electrolysis.