Chemical looping type process for iron-based green hydrogen storage and recovery

Details

Supervisors

De Wilde, Juray

Faculty

Ecole polytechnique de Louvain

Degree label

Master [120] : ingénieur civil en chimie et science des matériaux, à finalité spécialisée

Abstract

enThe transition towards a low-carbon energy economy requires not only efficient hydrogen production but also safe and scalable hydrogen storage and transport vector solutions. Chemical Looping Water Splitting (CLWS) using iron-based catalyst acts as a promising ”chemical battery” concept, offering a complementary pathway to electrolysis by storing energy in solid iron and releasing high-purity hydrogen on-demand through steam oxidation without requiring energy-intensive compression or complex gas separation. However, scaling up this storage and release technology requires a reliable understanding of the underlying reaction kinetics. Therefore, this master’s thesis aims to evaluate the kinetic behavior of a chromium-doped iron-based catalyst during the steam oxidation step and to use this data to simulate the process at the reactor scale. First, an experimental campaign was conducted in a laboratory setup at temperatures ranging from 580°C to 680°C. The structural and chemical stability of the material was successfully confirmed over 10 consecutive redox cycles. The collected data allowed for the observation of hydrogen production yields and mass balance consistency under varying space times and partial pressures. Based on these experimental results, a comprehensive kinetic modeling study was performed. Different approaches, including the Shrinking Core Model (SCM) and Langmuir-Hinshelwood-Hougen-Watson (LHHW) mechanisms, were developed and tested. The results demonstrated that a dissociative LHHW mechanism combined with a mixed gas-solid diffusion approach provided the most robust fit across all temperatures simultaneously. This optimization allowed for the extraction of key physical parameters, such as the activation energy, the adsorption enthalpy, and the effective diffusion coefficients. Furthermore, a specific investigation into the stoichiometric impact of chromium co-oxidation improved the model’s accuracy, providing new insights into the material’s behavior. Finally, the validated kinetic parameters were implemented into a 1D continuous mathematical model to simulate an isothermal fixed-bed tubular reactor. The numerical simulations successfully predicted the spatial and temporal dynamics of the steam oxidation step, clearly illustrating the propagation of the solid conversion front along the reactor and the total saturation time of the catalytic bed. Overall, this work bridges the gap between micro-scale reaction mechanisms and practical reactor engineering, providing a reliable predictive tool to support the future design and scale-up of CLWS-based hydrogen storage systems.