Session: 01-02: Decarbonizing Commodity Chemicals and Emissions Analyses

Paper Number: 169838

169838 - Modeling and Experimental Validation of a Ridged Flow Cell Design for Reduction of Mass Transport Limitation in a Ph-Shifting Electrochemical Device for Oceanic Co2 Removal 

Abstract: 

Carbon dioxide capture and removal technologies are critical to limit global warming to 2 °C. In this regard, ocean water CO2 capture can complement Direct Air Capture (DAC) technologies. In addition to the atmosphere, the oceans are huge sinks for carbon and have to-date captured about 25% of all anthropogenically released carbon. Previously, we have presented the performance of a new, reversible, electrochemical device that combines hydrogen and ferrocyanide redox salt looping to capture CO2 from ocean water via pH-shifting [1]. With concerns of mass transport and ohmic resistance limitations, custom manufactured flow plates were designed to reduce these limitations. For improving mass transport of the redox salt, a computational design study was performed to identify design/operational strategies to increase the operating current densities by lowering concentration/diffusion boundary layer thickness. We explore the effects of passive flow mixers adding ridges/fins to interior surfaces of serpentine flow channels. Computational fluid dynamic modeling was used to quantify effects of fluid flow rate and the ridge parameters including thickness, spacing, and orientation on both the reductions that can be achieved in the boundary layer thickness and the impact on pressure drop. Additionally, we simulated the effects of active flow mixing via pulsed fluid flow conditions through these flow channels. Model predictions are used to select ridge designs and pulsed flow conditions to perform experimental testing on. Specifically, our experimental tests on flow cells demonstrate enhanced mass transport with up to 40% increase in the limiting current densities for a flow rate of 10 mL/min with the use of ridges as compared to the base case without ridges. While ohmic resistances are also addressed through reducing channel thickness, ohmic resistances remain a significant challenge in achieving commercially viable (>100 mA/cm^2) current densities for electrochemical pH-shifting methods of oceanic CO2 removal.

[1] Rachel Silcox, Rohini Bala Chandran, Demand-side flexibility enables cost savings in a reversible pH-swing electrochemical process for oceanic CO2 removal, Cell Reports Physical Science, Volume 5, Issue 3, 2024, 101884, ISSN 2666-3864, https://doi.org/10.1016/j.xcrp.2024.101884.

Presenting Author: Rachel Silcox University of Michigan

Presenting Author Biography: Rachel earned her Bachelor’s in Mechanical Engineering from Valparaiso University in 2019. She worked for one year at a green hydrogen start-up company and as a statistics/environmental science teaching assistant at Pannasastra University of Cambodia, Siem Reap. For her Ph.D. work she is focusing on electrochemical modeling and flow reactor design and testing for ocean water carbon capture and water treatment applications. Rachel is a recipient of the NSF Graduate Research Fellowship (2021) and the University of Michigan's Rackham Predoctoral Fellowship (2025).