From fundamental principles to experimental developments

Human activities have pushed several planetary boundaries beyond their safe operating limits, calling for a profound transformation towards a more sustainable society. Achieving a sustainable society requires, notably, profound changes in industrial production. Among the most challenging sectors, the cement and lime industries remain major contributors to global CO₂ emissions. In this context, this thesis investigates a novel electrochemical pathway for calcium hydroxide production. This approach offers the potential to fundamentally redesign lime and cement manufacturing with a reduced environmental footprint, although it currently remains at a low technology readiness level. The process was experimentally investigated in two-compartment cells. Excess and batch feedstock addition strategies, as well as in-situ and ex-situ precipitation methods, were compared. Based on the theoretical framework developed in this work and experimental results, key guidelines are established to achieve the desired stoichiometry throughout water electrolysis, feedstock dissolution, ion migration, and calcium hydroxide precipitation. The limited CO₂ recovery caused by gas-liquid mass transfer limitations was identified, and strategies to overcome this limitation are proposed. Membrane fouling, responsible for voltage instability, was characterized under various operating conditions and strategies to prevent calcium carbonate contamination during ex-situ precipitation are provided. The influence of various natural feedstocks was also investigated. The effect of particle size distribution on dissolution, the congruence of impurity dissolution, and the feasibility of using reclaimed mortar as an alternative feedstock were assessed. The properties of the resulting calcium hydroxide products were compared. Finally, the energy requirements and prospective CO₂ emissions of the process are assessed together with other environmental implications. This work establishes the fundamental principles governing electrochemical calcium hydroxide production and provides a coherent framework for its future scale-up. The findings also demonstrate the potential of the electrochemical route to improve both process performance and the sustainability of lime and cement production.

Membres du jury :

• Prof. Joris Proost (UCLouvain)(Promoteur)
• Prof. Paul Fisette (UCLouvain) (Président)
• Prof. Patricia Luis Alconero (UCLouvain) (Secrétaire)
• Prof. Tom Leyssens (UCLouvain) 
• Prof. Diane Thomas (UMons)
• Dr. Aurélien Chardon (Carmeuse)

Soutenance publique également accessible par visio-conférence via le lien (TEAMS) : 

https://teams.microsoft.com/meet/342087054716503?p=RZyhRoDKFJUO9ZWZwW

Sustainable hydrogen is expected to play a significant role in the energy transition, as it offers a way to store and deliver usable and clean energy while avoiding direct carbon dioxide emissions at the point of use. The objective of this thesis is to propose strategies to enhance the performance of alkaline water electrolysis and thereby contribute to the development of more efficient electrolyser designs. To this end, computational fluid dynamics (CFD) simulations are used to investigate transport phenomena within water electrolysis cells at both laboratory- and prototype-scales. At laboratory-scale, the incorporation of flow-engineered, laterally graded bilayer electrodes within laboratory cells is considered under forced electrolyte flow conditions. Complex three-dimensional (3D) materials, such as metallic foams and triply periodic minimal surfaces (TPMS) structures, are investigated through a pore-resolved CFD approach. At prototype-scale, flow distribution is quantified using residence time distribution (RTD) analyses. Single-phase flow simulations are used to study flow uniformity and the presence of recirculation regions depending on the inlet configuration and the porous transport layer (PTL). Multiphase flow simulations are subsequently introduced to account for electrogenerated hydrogen bubbles and to investigate the influence of cell geometry on gas distribution and evacuation. Overall, the findings presented here suggest that unlocking the full potential of industrial alkaline water electrolysers will require a more integrated approach to electrolyser design, in which flow fields, porous electrodes, gas evacuation pathways, and cell architectures are co-designed. Such an approach provides a pathway towards more uniform liquid distribution, improved gas evacuation, and more efficient use of the active electrode area, thereby supporting the development and scale-up of high-performance alkaline water electrolysers.

Membres du jury :

• Prof. Joris PROOST (UCLouvain)(Promoteur)
• Prof. Aude SIMAR (UCLouvain) (Président)
• Prof. Juray DE WILDE (UCLouvain) (Secrétaire)
• Prof. Alessandro MONTEVERDE (Politecnico di Torino) 
• Prof. Benoit SCHEID (ULB)

Soutenance publique également accessible par visio-conférence via le lien (TEAMS) : 

https://teams.microsoft.com/meet/3384295413583438?p=R65BqdXQbIKZUkHibx