Advancing carbon dioxide capture: investigation into the kinetics and efficiency of absorption in molten calcium oxide-chloride

Hall, Melissa; Rigby, Sean P.; Chen, George Zheng

Abstract

One promising carbon capture technology is the absorption of carbon dioxide (CO2) by molten salt, specifically the molten mixture of calcium oxide and chloride (CaO + CaCl2, COC), as it solves some of the key issues with alternative methods, including thermal stability and capture efficiency. The kinetics of CO2 absorption in a column of COC is examined by deriving a simple kinetic model and determining the kinetic constants under various conditions. The model emphasises the importance of the oxide anion (O2−) concentration and CO2 partial pressure in driving the absorption rates. Applying this model to reported experimental data on CO2 absorption with varying molten salt height, or CaO wt% in molten CaCl2 produced values for the kinetic constants with high accuracy. The fastest rate of absorption, with a rate constant of 0.00313 L mol−1 min−1 was achieved at a 15 cm molten salt height. Conversely, the slowest rate, 0.00062 L mol−1 min−1, occurred at 20 wt% CaO in CaCl2. Comparative analysis with conventional amine-based CO2 capture systems reveals a slower absorption rate for the molten salt. Nonetheless, there are further elements which need to be explored to perform a full comparison with the amine system, for example the desorption kinetics or absorption capacity. This reinforces the need for further research into molten salt absorption kinetics to gain a more holistic understanding of this technology and enable an optimal process design for further assessment of the feasibility and scalability of molten salt-based CO2 capture in current and future processes. Ultimately, this will promote the adoption of carbon capture technology, cultivating more sustainable practices in industry.

Citation

Hall, M., Rigby, S. P., & Chen, G. Z. (2024). Advancing carbon dioxide capture: investigation into the kinetics and efficiency of absorption in molten calcium oxide-chloride. RSC Sustainability, 3, 341-351. https://doi.org/10.1039/d4su00354c

• Journal Article Type: Article
• Acceptance Date: Oct 24, 2024
• Online Publication Date: Oct 24, 2024
• Publication Date: Oct 24, 2024
• Deposit Date: Oct 28, 2024
• Publicly Available Date: Oct 28, 2024
• Journal: RSC Sustainability
• Print ISSN: 2753-8125
• Electronic ISSN: 2753-8125
• Publisher: Royal Society of Chemistry
• Peer Reviewed: Peer Reviewed
• Volume: 3
• Pages: 341-351
• DOI: https://doi.org/10.1039/d4su00354c
• Public URL: https://nottingham-repository.worktribe.com/output/41134550
• Publisher URL: https://pubs.rsc.org/en/Content/ArticleLanding/2024/SU/D4SU00354C