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

Journal of Physics: Conference Series PAPER • OPEN ACCESS High-temperature electrolysis for industrial decarbonisation: a real-scale demonstration in the steel sector To cite this article: Martina Fantini et al 2025 J. Phys.: Conf. Ser. 3143 012073 View the article online for updates and enhancements. You may also like EnerCmed Project: Advancing EnergyPositive and Climate-Resilient Hinterlands through Renewable Energy Communities and Nature-Based Solutions Jonathan Roberts, Augusto Bocanegra, Davide Borelli et al. - The Effect of Steam-Oxygen Gasifying Medium on Syngas Upgrading for Nitrogen Reduction Marco Puglia, Bear Kaufmann, Jim Mason et al. - A comparison between the software EUReCA and UrbanEnergyPro on a district in Germany Michele De Carli, Leonhard Odersky, Enrico Prataviera et al. - This content was downloaded from IP address 95.226.59.46 on 15/12/2025 at 10:54 Content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI. Published under licence by IOP Publishing Ltd ATI Annual Congress (ATI 2025) Journal of Physics: Conference Series 3143 (2025) 012073 IOP Publishing doi:10.1088/1742-6596/3143/1/012073 1 High-temperature electrolysis for industrial decarbonisation: a real-scale demonstration in the steel sector Martina Fantini1*, Elena Crespi2, Andrei Denissenko3, Minna Toivola4, Claudio Leoncini5, Felix Kaiser6, Silvia Rossetti7, Stephen J. McPhail8, Giovanni Camarda9, Giulio Guandalini10, Paolo Colbertaldo10 and Stefano Campanari10 1 EU CORE Consulting, Via XX Settembre 98/E, 00187 Rome, Italy 2 FONDAZIONE BRUNO KESSLER, Via Santa Croce 77, 38122 Trento, Italy 3 AKTSIASELTS ELCOGEN, Valukoja 23, 11415 Tallinn, Estonia 4 ELCOGEN OY, Niittyvillankuja 4, 01510 Vantaa, Finland 5 TENOVA, Via Gerenzano, 58, 21053 Castellanza (Varese), Italy 6 RWTH-AACHEN IOB, Kopernikusstraße 10, 52074 Aachen, Germany 7 ACCIAI SPECIALI TERNI, Viale Benedetto Brin 218, 05100 Terni, Itlay 8 KIWA Corporation, Sir Winston Churchilllaan 273, 2288 EA Rijswijk, Netherlands 9 Baker Hughes, Via Felice Matteucci 2, 50127 Firenze, Italy 10 Politecnico di Milano, Energy Department, via Lambruschini 4A, 20156, Milano *E-mail: [email protected] 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 CO2 emitters, requiring innovative solutions to reduce fossil fuel dependency while maintaining eficiency 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 MWel 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 eficiency (speciic consumption below 37 kWhel/kgH2), utilizes steam recovered from the steel reheating process, signiicantly reducing electricity demand compared to lowtemperature electrolysis technologies. This approach not only lowers operational costs but also optimises energy use within the steelwork, demonstrating a costeffective and scalable hydrogen production model. ATI Annual Congress (ATI 2025) Journal of Physics: Conference Series 3143 (2025) 012073 IOP Publishing doi:10.1088/1742-6596/3143/1/012073 2 Hydrogen produced on-site will be directly fed into a high-eficiency, fuel-lexible slab reheating furnace, designed for progressive decarbonisation through hydrogen combustion. The furnace can operate with variable H2-natural gas mixtures, reducing CO2 emissions by 5,600 tonnes per year during the project and up to 35,700 tonnes per year with future expansion. Additionally, the oxygen byproduct from electrolysis is recovered and reintegrated into the process, further optimizing combustion eficiency 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 irst 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 eficiency 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 eficiently redirected to support electrolysis. Keywords: SYRIUS, steel industry, decarbonisation, Solid Oxide electrolysis 1. Introduction The steel industry is one of the largest energy consumers, with an average of 5.2 MWh of primary energy per tonne of steel produced. In terms of emissions, this results in 9% of all anthropogenic CO2 emissions worldwide [1], showing an increasing tendency since steel production is expected to grow by more than a third within 2050 [2]. Of the total current steel production, 78% is attributed to the “primary route”, which utilizes iron ore as feedstock to produce virgin steel. Within this segment, 70% of the output is generated through the Blast Furnace-Basic Oxygen Furnace (BF-BOF) technology, using coal as main fuel and being responsible for the majority of steel output and related global CO2 emissions. The remaining nearly 8% of steel within this primary route category is produced using Direct Reduced Iron (DRI) technology (followed by Electric Arc Furnace (EAF) processing), using natural gas as main fuel. The “secondary route”, based on EAF and using scrap steel as main feedstock, has lower energy demand and carbon footprint [3] and it currently covers the remaining 22% of world steel production (41.5% in the EU, with peaks of 81% in Italy and 61% in Spain). Producing 1 tonne of steel with EAF results in the emission of approx. 0.3-0.6 tCO2 per tonne of steel, vs. the typical 2.2 tCO2 per tonne of steel for the BF-BOF route, including both the direct emissions from fossil fuels use and the indirect emissions deriving from electricity consumption at average grid carbon intensity [2, 4]. ATI Annual Congress (ATI 2025) Journal of Physics: Conference Series 3143 (2025) 012073 IOP Publishing doi:10.1088/1742-6596/3143/1/012073 3 There are several technological pathways towards a lower carbon intensity for the steel industry that, in the most considered options, relate to the upstream crude steel production [5], (i) employ different approaches for iron ore reduction, such as the DRI route, and (ii) increasingly integrate the use of renewable electricity and green hydrogen as input energy vectors or implement CO2 capture and storage (CCS) options. Independently from the crude steel production pathways, signiicant CO2 emissions are related to the hot rolling mill processes occurring downstream the cast steel production [6]. Among the most important sources of direct CO2 emissions at this stage there are hightemperature processes, such as the steel slab reheating or the heat treatment (e.g. annealing) of steel products. Steel reheating, in particular, is adopted for most crude steel processing, apart from the few productions employing a continuous casting and rolling approach. A typical steel reheating furnace consumes nearly 32 Nm3NG per tonne of steel [7] (or other fossil fuel such as syngas from BF-BOF plants) to reach steel slab temperatures above 1,200°C prior to the hot rolling lamination process. The resulting CO2 emissions (61 kgCO2/t of steel) are therefore present in nearly all crude steel processing routes and are among the most important direct emissions (Scope 1) in the case of EAF steelmaking. Decarbonization of such processes entails the introduction of electriication (e.g. induction heating, currently feasible only for certain sizes and limited maximum temperatures) or the use of clean fuels such as hydrogen. Hydrogen is, in fact, considered the irst candidate to replace fossil fuels in steelmaking, both in primary production (substituting coal as a reducing agent) and in secondary steelmaking [8]. The urgency to integrate hydrogen-based methods in sustainable steel production routes is not without challenges. While the production of renewable-based green hydrogen through lowtemperature water electrolysis already offers relatively low speciic capital costs and demonstrated durability, high-temperature Solid Oxide Electrolysis (SOEC) technology may offer unmatched conversion eficiency and lower electricity consumptions, especially when coupled with heat recovery from the industrial process for supplying steam to the electrolyser. However, current state-of-the-art SOEC systems struggle with producing hydrogen at the necessary rate and cost, and they are not yet compatible for coupling with the demand of industrial processes at the required scale and with a suficiently demonstrated reliability (e.g., tens kW of SOEC electrolyser are required to supply hydrogen to a DRI plant vs several tens MW for a single slab reheating furnace and vs several hundred MW scale electrolysis for a full-scale DRI installation). Within this framework, the SYRIUS project [9] aims to address such challenges by integrating a 4.2-MWel SOEC at the existing EAF-based steel production plant in Terni, Italy (Figure 1), to produce 100 kg/h of green hydrogen. This hydrogen will supply an 84 MWth slab reheating furnace (WBF, walking beam furnace), showing the potential to reduce CO2 emissions of the steel reheating production step process by: (i) 5,600 t/y or 4.3% of furnace emissions during the project; (ii) up to 35,700 t/y or 27% of furnace emissions in a future expansion at larger scale (25 MW SOEC with maximum heat recovery from the furnace); (iii) or up to 100% in case of full hydrogen feeding of the furnace, combined with heat recovery from other waste heat sources in the steelwork processes, such as directly from the EAF. By generating steam through furnace offgas heat recovery, implementing by-product oxygen recovery in the furnace (allowing additional savings of 430 tCO2/year in SYRIUS and of 2% fuel input in future expansion) and analysing options for water recycle, SYRIUS seeks to minimize external energy consumption and sets industrial circularity at the project core. The purpose of the following work is to present an overview of the project and the progress of the irst six months of SYRIUS activities. ATI Annual Congress (ATI 2025) Journal of Physics: Conference Series 3143 (2025) 012073 IOP Publishing doi:10.1088/1742-6596/3143/1/012073 4 Figure 1. Acciai Speciali Terni plant in Italy 2. SYRIUS: concept and methodology 2.1 Concept SYRIUS is an innovation action supported by the Clean Hydrogen Partnership and co-funded under the Horizon Europe research programme, that, spanning 54 months, aims at tackling the most polluting phase of the steel-making process, steel heating, by simultaneously advancing innovative stack and module designs of high-temperature electrolysis (SOEC) and demonstrating its integration for more than 5,000 working hours at a relevant scale in operational environment (TRL7) – namely at the Acciai Speciali Terni SPA (AST) steel plant in Terni, Italy – including a full recovery of the produced oxygen and its utilization, together with hydrogen, in a fuel-lexible slab reheating furnace. The partnership consists of three research organizations and nine industrial partners which include two leading European universities, one research center, major players in steel production and hydrogen certiication, as well as several technology providers. Figure 2 shows the various partners and the location within Europe. ATI Annual Congress (ATI 2025) Journal of Physics: Conference Series 3143 (2025) 012073 IOP Publishing doi:10.1088/1742-6596/3143/1/012073 5 Figure 2 . SYRIUS Consortium Signiicant effort is being directed towards the integration of the SYRIUS concept in the pilot plant and demonstration activities to achieve ambitious targets. Figure3 illustrates the basic concept of SYRIUS when integrated in the AST steel plant in Terni, Italy, one of the most important integrated steelmaking sites in Europe in the stainless-steel sector with more than 1 million tonnes of stainless and specialty steel produced per year. The integrated system is constitued by individual units at different maturity level (TRLs): i) a high-temperature SOEC: it offers high electrical eficiency for hydrogen production, especially when integrated with waste heat recovery from external sources, such as industrial processes. While the core materials and stack architecture are robust, the operation in electrolysis mode still faces key challenges in particular in long-duration performance, current density optimisation, and cost reduction. Currently, the technology is positioned at TRL5 with previous experiences validating performance but not yet demonstrating full system reliability at scale. SYRIUS will advance SOEC technology to TRL7 by developing a multi-stack 4.2 MW system with improved current density (from 0.5 to 0.75 A/cm2), optimized hot balance-of-plant, and long-term testing under real industrial load proiles. CAPEX will be reduced through modularisation and design-for-manufacturing strategies, positioning the SOEC as a scalable building block for industrial hydrogen deployment; ii) a lexible hydrogen and oxygen-enriched air burner: modern steel furnaces increasingly adopt lameless combustion to reduce NOx and CO2 emissions, and hydrogen-ready burners have reached TRL8-9. However, challenges remain in process integration, control of combustion atmospheres, and safe, continuous hydrogen supply. SYRIUS will advance the state of the art by demonstrating a lexible burner coupled with a high-temperature SOEC at multi-MW scale in a real production environment. The burner will operate with variable ATI Annual Congress (ATI 2025) Journal of Physics: Conference Series 3143 (2025) 012073 IOP Publishing doi:10.1088/1742-6596/3143/1/012073 6 H2/NG ratios, enriched with oxygen recovered from the SOEC, offering both fuel and oxidant lexibility. The system will be tested in an operational furnace, assessing impacts on combustion stability, emissions, and material treatment outcomes. This full-scale integration (combining on-site hydrogen and oxygen use) will bring the overall solution to TRL8 and deliver key insights into infrastructure, safety, optimized combustion eficiency and process control requirements for future hydrogen-based industrial furnaces; iii) a heat recovery integration with SOEC: heat recovery systems in steel plants are mature (TRL9), but their integration with high-temperature electrolysers is untested. In SYRIUS, a key innovation lies in adapting the conventional steam recovery infrastructures of the AST steel plant to support the SOEC. This requires the design and control of a dual-loop system, where thermal energy from the reheating furnace is used to generate high-purity steam for electrolysis. Speciic attention will be given to ensuring stable steam supply at adequate temperature during partial load or transient furnace operation. Advanced control logic will manage the interaction between the furnace, the heat exchanger, and the electrolyser to guarantee operational reliability. In addition, SYRIUS will explore the recovery of low-grade heat and condensation water for puriication and reuse, contributing to circularity. This demonstration will represent a irst-of-a-kind application, raising the TRL of heat recoverySOEC integration from TRL7 to TRL8 within a fully industrial context. iv) a process integration including Energy Management System (EMS): currently, SOEC systems are operated as steady-state, base-load units, controlled by relatively simple PID logic. This approach overlooks opportunities for cost and emissions optimisation in response to luctuating electricity prices and renewable generation. SYRIUS will introduce a major innovation by integrating an advanced EMS, based on model predictive control, capable of dynamically optimizing SOEC operation when integrated with PV plants and batteries to form a Virtual Power Plant. The EMS will take into account of the forecasts of PV production proiles, Battery operational constraints and SOEC part-load eficiency curve, operational constraints (e.g., start-up and ramp-up limits) and operating costs (including those associated to the degradation) to determine the cost-optimal management solution for the virtual power plant. The EMS, developed over the last 10 years by Politecnico di Milano (POLIMI), is based on a detailed Mixed Integer Linear Programming (MILP) model of the virtually aggregated plant. Demonstration in an industrial setting will bring the EMS and SOEC integration from TRL5 to TRL7. Additionally, Politecnico di Milano will explore the optimal long-term design of fully renewable energy systems powering hydrogen production, using advanced Mixed Integer Linear Program (MILP)-based planning tools. This comprehensive integration aims at positioning the SOEC not as a stand-alone device, but as a responsive, optimised asset within a smart industrial energy ecosystem. Through the set of demonstration activities in relevant environment planned in SYRIUS, the system will reach TRL7 for the core part (the electrolysis plant) and TRL8-9 for the other plant and project components. The project aligns with the broader ambition of the steelmaking sector to identify and implement the most effective combination between all the available technologies and fuels, with the purpose of producing high-quality products at the lowest achievable carbon footprint, without giving up competitiveness. ATI Annual Congress (ATI 2025) Journal of Physics: Conference Series 3143 (2025) 012073 IOP Publishing doi:10.1088/1742-6596/3143/1/012073 7 Figure 3 . SYRIUS Concept and plant integration. 2.2 Methodology To integrate the SOEC in the real electric arc furnace steelmaking environment, SYRIUS follows a structured and progressive implementation strategy. The methodology is articulated in ive main phases: 1. analysis, 2. development, 3. integration, 4. demonstration, and 5. impact assessment. Each phase builds upon the results of the previous one, ensuring technical continuity and readiness for real-scale deployment. In the irst 18 months, the project focuses on the analysis and preparatory work required to adapt the existing infrastructure at the AST steel plant in Terni. This involves deining the design ATI Annual Congress (ATI 2025) Journal of Physics: Conference Series 3143 (2025) 012073 IOP Publishing doi:10.1088/1742-6596/3143/1/012073 8 parameters and operational requirements for integrating the 4.2 MW SOEC plant, performing a comprehensive risk and safety assessment, and addressing permitting and regulatory compliance. During this phase, signiicant effort is dedicated, in particular by Politecnico di Milano and Fondazione Bruno Kessler (FBK), to the co-design of interfaces between the SOEC and the reheating furnace, including the modelling of the steam loop that will feed the electrolyser with process heat recovered from lue gases. Parallel to this, the project will initiate the detailed engineering of the SOEC multi-stack module and its associated systems. Key aspects include the optimisation of stack layout for thermal stability and maintenance, carried out by ELCOGEN, the development of a larger scale SOEC module, carried out by Baker Hughes (BH), and the pre-certiication of the system for safe industrial deployment under the scope of Kiwa and its afiliated Vinçotte. Before scaling up to the 4.2 MW plant, a smaller prototype module, around 100 kW, will be tested under controlled conditions at Baker Huges’s facilities in Florence. This intermediate step will enable early validation of performance targets, safety aspects, and component integration, reducing risks prior to the full-scale implementation. In terms of control architecture, the early phases will involve the deinition of a smart EMS, capable of coordinating hydrogen production, storage, and usage. This EMS, joint effort of Politecnico di Milano and Fondazione Bruno Kessler, will be designed to optimise operations in response to dynamic electricity prices and variable renewable availability, leveraging virtual aggregation schemes as allowed by the Italian regulatory framework. The EMS development will follow a hybrid modelling approach combining long-term planning and real-time optimisation. From a plant integration point of view, the SYRIUS methodology foresees the design of dedicated interconnections for steam, electricity, and gas lows between the SOEC system and the steel plant infrastructure. Wherever possible, existing components at the Acciai Speciali Terni site will be reused and adapted to minimise disruptions and facilitate integration. The heat recovery system will be designed to ensure the generation of steam with suitable pressure and temperature levels for the electrolyser, even under variable furnace operating conditions. A central element of this integration is the new slab reheating furnace developed and provided by Tenova, designed for full industrial operation with hydrogen-natural gas blends up to 100% H2. This furnace will receive both hydrogen and oxygen-enriched air produced by the SOEC and will serve as the main testbed for evaluating thermal eficiency, emissions reduction, and impacts on steel quality. Additionally, as depicted in Figure 3, the lue gases from this furnace will be used as the primary heat source for the steam feeding the SOEC, creating a highly eficient circular system. Tenova also contributes to the design and optimisation of the heat recovery and lue gas handling infrastructure to ensure stable and safe operation under real load conditions. To support the whole process anlysis and integration, dedicated simulation activities will be conducted starting from the early phases of the project. These will include a process model in Aspen Plus®, enriched with a speciic SOEC component, and a dynamic model developed in Modelica. These tools will help predict system behaviour under steady-state and transient scenarios, support the design of the EMS, and enable the deinition of robust control and optimisation strategies. In the inal phase, Aachen University will play a key role by leading the life cycle assessment (LCA) of the SYRIUS system, applying internationally recognised standards to quantify the environmental impacts and circularity potential of the integrated process, thus providing robust evidence of its sustainability for future industrial uptake.