Numerical Modeling and Size Optimization of Thermal Energy Storage for Iron and Steel Production

Iron and steel production is one of the major energy consumers in the United States because of the higher temperature processes and low energy efficiency. Hydrogen direct reduction of iron (H2DRI) is a promising alternative pathway for iron production to conventional technologies relying on natural gas. The H2DRI process requires hydrogen at temperatures up to 950degrees C, fed into a reduction furnace to produce pellets or briquettes used in downstream steelmaking. This work proposes an electrical thermal energy storage (ETES) system utilizing renewable electricity to store and dispatch high-temperature heat, buffering the H2DRI plant from electricity price variability. We developed heat transfer models for two ETES systems: a particle-based ETES and a firebrick ETES, evaluating their performance, sizing, and preliminary costs. The firebrick ETES system, with a storage volume of 250 m3, provides less than 3 hours of continuous operation, limiting its price buffering capability unless significantly oversized. The particle ETES heat exchanger requires approximately 140 rows to meet the thermal demand of 6.78 kg/s of H2, achieving high effectiveness but incurring a significant pressure drop (~29 bar), mitigated by hydrogen supply pressures from PEM electrolysis. Results demonstrate that both ETES options are feasible for industrial-scale H2DRI, with the firebrick system being more compact and modular for smaller-scale applications, while the particle ETES system provides higher scalability. Future work should focus on integrating these models into a techno-economic analysis to assess their commercial viability.