Session: Research Posters

Paper Number: 120001

120001 - Analysis of Electrochemical Capture of Co2 From Oceanwater Coupled With Hydrates-Based Seabed Sequestration 

While significant decarbonization-related efforts are underway, it is becoming increasingly clear that the planet is not going to decarbonize quickly enough to mitigate the increasing negative effects of climate change. Negative emission technologies will need to be implemented at large scales to reduce excess CO₂ in the earth’s atmosphere and oceanwater. Despite significant research, direct air capture continues to be expensive and challenging due to the difficulty of removing low concentrations of CO₂ from air. Removing CO₂ from oceanwater offers certain advantages. The ocean absorbs large amounts of atmospheric CO₂ (up to 40% of all anthropogenic CO₂ emissions since the industrial revolution). While this absorption has helped in reducing atmospheric CO₂ concentrations, it has come at the cost of ocean acidification and harm to ocean life. Ocean concentrations of CO₂ on a volumetric basis are 100 mgL^‑1 compared to just 0.77 mgL^‑1 of atmospheric air which highlights the benefits of CO₂ from oceanwater. Removing CO₂ from surface ocean water will directly benefit pH of ocean water, as well as indirectly remove CO₂ from the atmosphere.

This study analyzes a plant to remove CO₂ from surface oceanwater, which is coupled to long-term, stable storage of CO₂ via the formation of CO₂ hydrates (ice-like materials of and CO₂ and water, which form at temperatures of ~ 0 C and pressures > 350 psi). CO₂ hydrates (which are sealed) offer a pathway to long-term sequestration on the seabed which provides a stable environment for hydrates.

In this study, a first-order assessment of an integrated ocean electrochemical CO₂ capture plant coupled with subsea sequestration via CO₂ hydrates is conducted. The system is located on an off-shore platform to enable surface water CO₂ capture (which allows for the water to passively exchange further CO₂ with the atmosphere). The captured CO₂ is then compressed and formed into a CO₂ hydrate slurry, which is formed by bubbling CO₂ through water in a bubble column reactor. This hydrate slurry is compacted to form plugs which are sealed in an impermeable polymer and sent down to the seabed for permanent sequestration.

The analysis involves the development of a system-level model which simulates key aspects of electrochemical CO₂ capture and hydrates-based sequestration. This model considers all key process phenomena and equipment involved in this process. Technical inputs from the electrochemical capture model come from state-of-the-art literature on an asymmetric chloride-mediated electrochemical capture process. Key inputs include the energy requirement per mole of CO₂ captured as well as the power requirements for the relevant pumping, filtering, etc. Key inputs for hydrate formation in bubble column reactors comes from a computational model relating bubble size, CO₂ flowrates etc., to hydrate formation rate.

The model can predict CO₂ capture rates, hydrate formation rates, overall power and cooling for this coupled ocean capture and hydrates-based sequestration system. The model can be used to examine various constraints on this concept, conduct optimization studies and study techno-economic feasibility of this concept.

Presenting Author: Mark Hamalian UT Austin

Presenting Author Biography: M. Hamalian received a B.A. degree in physics from Stonehill College, Easton, MA, and a B.S. degree in mechanical engineering from the University of Notre Dame, Notre Dame, IN in 2019. He is currently pursuing a Ph.D. degree in mechanical engineering at the University of Texas at Austin, Austin, TX.
His research interests include enhanced heat transfer applications, carbon capture and storage (CCS) technologies, renewable energy technologies, and CO2 gas hydrates.
Mr. Hamalian’s awards and honors include the National Science Foundation Graduate Research Fellowship (2023) and the Cockrell School of Engineering Fellowship (UT Austin).

Authors:

Mark Hamalian UT Austin
Awan Bhati University of Texas at Austin
Vaibhav Bahadur University of Texas at Austin