title: Study of Carbon Dioxide Capture Using Novel Calcium Oxide-Based Sorbents in Powder, 3D-Printed Monolith, and Pellet Forms within the Calcium Looping Process
Creators: name: Vijayaraghavan Ramesh, Aakash
Publisher: name: Schulich School of Engineering
Year: 2024
Subjects: subject: Engineering--Chemical

description: Decarbonization is critical to mitigating the most severe effects of climate change, such as sea level rise and extreme weather events. It involves reducing carbon dioxide (CO2) emissions to limit global warming to below 1.5ºC above preindustrial levels, as emphasized by the Intergovernmental Panel on Climate Change (IPCC) [1]. CO2 capture, utilization, and sequestration (CCUS) has emerged as a key technology for different sectors, trapping CO2 from industrial sources and either storing or repurposing it. Although promising, CCUS faces high costs, regulatory hurdles, and public opposition, yet global efforts to scale up are progressing. Post-combustion capture, the most established method, uses chemical solvents and solid sorbents to extract CO2 from flue gas, but faces sustainability and cost challenges for large-scale implementation. Ongoing research aims to improve efficiency and reduce environmental impacts. Calcium looping (CaL) has gained attention for its fast sorption kinetics, high uptake capacity, and low cost. However, a key barrier to commercialization is the loss of sorbent capacity and stability over multiple cycles. This thesis explores the fabrication of synthetic CaL sorbents, focusing on achieving high CO2 uptake and stability during cyclic operations. This study investigates the development and performance of CaO-based sorbents enhanced with high-Tammann-temperature metal stabilizers to improve CO₂ capture efficiency in the calcium looping (CaL) process. Stabilizers were integrated into the CaO lattice in mono-, bi-, and tri- metallic configurations, using a molar ratio of 1:10 (M:Ca). While CaL is a promising CO₂ capture technology for large emitters, several challenges remain in scaling up synthetic CaO-based sorbents. These sorbents exhibit low bulk density, high surface area, and poor flowability, leading to high pressure drops, material handling difficulties, and potential blockages in industrial units. Fluffy, lightweight sorbents are also prone to agglomeration, reducing CO₂ capture efficiency and increasing material loss via entrainment in flue gas, which raises operational costs. The tendency of these materials to form clumps also complicates the regeneration process, impacting structural integrity and health safety. Fabricated as 3D prints, pellets, and spheronized forms, these sorbents maintain stability despite reduced CO₂ uptake due to surface area and diffusion limitations compared to powdered forms. Despite these challenges, advanced bi- and tri-metallic sorbent configurations show potential for mitigating some of these limitations, marking significant progress toward scalable, efficient CaL- based CO₂ capture solutions for decarbonizing carbon-intensive industries. This research introduces a novel approach to create highly stable CaO-based sorbents with multiple metal supports for the calcium looping process. This advancement has the potential to facilitate the large- scale deployment of this process.