Session: 11-01 Carbon Capture and Sequestration

Paper Number: 105811

105811 - Modeling the Performance of a Novel Microchannel-Based Mass Exchanger for Carbon Capture 

There is growing consensus that significant removal of atmospheric CO₂ will be needed to limit Earth’s temperature rise to < 1.5 C. Estimates on CO₂ removal capacity needs are as high as 10 Gigaton/yr, i.e., 1/4th of CO₂ emissions in 2021. Currently, absorption of CO₂ into an aqueous amine solution followed by thermal/pressure swing-based sorbent regeneration is the most mature technology. Key challenges associated with it include large energy consumption for sorbent regeneration and large, heavy, CAPEX-intensive equipment, especially for CO₂ capture from dilute streams. As an alternative, we introduce and analyze a novel compact mass exchanger which is inspired by an analogous heat exchanger which has the capacity to absorb extreme heat fluxes (1/8th the flux on the sun’s surface). This mass exchanger involves air flow in microchannels lined with textured surfaces which are infused with CO₂ capture sorbent liquids (which are immobilized). The working of this mass exchanger involves a CO₂ capture phase followed by a CO₂ release phase in the same hardware (as opposed to distinct absorber and stripper columns in practice today). High absorption capacity is a consequence of significantly higher surface area/volume ratio and higher mass transfer coefficients (resulting from small hydraulic diameters). This study presents first order mathematical modeling to predict key performance parameters of this mass exchanger using aqueous monoethanolamine (MEA) as the sorbent.

To facilitate the design, we develop a model for the capture process in amine-infused grooves, accounting for diffusive transport of CO₂ and MEA in aqueous solution and their reaction into carbamate. It comprises two coupled reaction-diffusion equations for the CO₂ and MEA concentrations, which are solved transiently in the capture and release phases.  

The modeling framework is used to predict key system-level performance parameters of this mass exchanger. These include i) CO₂ removal capacity per unit volume of mass exchanger, ii) power consumption, iii) capture time and release time. These parameters are estimated for various working conditions which capture i) varying CO₂ concentrations, ranging from 0.04% (ambient air) to 20% (flue gas), ii) flow speeds, iii) various parameters associated with the mass exchanger (hydraulic diameter, texture height and porosity, etc). The performance of these mass exchangers is compared and contrasted with the conventional packed-bed architecture for carbon capture.  Overall, this study sets the stage for further analysis and development of new carbon capture technology.

Presenting Author: Michael Mayer Imperial College London

Presenting Author Biography: Michael Mayer is a postdoctoral research associate in the Department of Mathematics, Imperial College London, modeling transport phenomena on textured surfaces together with Prof Papageorgiou and Prof Crowdy at Imperial College, but also Prof. Hodes at Tufts University. He was awarded his PhD in Mechanical Engineering from Tufts University in 2022.