(130f) CO2 Adsorption Kinetic Model for Direct Air Capture

To successfully gear the planet towards a net-zero emissions scenario by 2050, direct air capture (DAC) is particularly crucial among the diverse collection of technologies currently employed in sequestering CO₂ as it could potentially resolve the emissions from small distributed sources which account for ~20% of total CO₂ emissions. In addition, the inherent benefits of DAC such as low requirements of land and water utilization and flexible location constraints, make it a promising candidate for DAC. Adsorption kinetic model plays a vital role in determining the performance of DAC sorbent for scale-up. In this work, a comprehensive model combining CO₂ adsorption reaction kinetics with external and internal pore diffusion under a fluid flow was studied. Both external mass transfer in the sorbent bed and intraparticle mass transfer within the sorbent particles are considered in the model. Equilibrium adsorption isotherms were determined from lab-scale experimental data under sub-ambient to ambient temperatures and relative humidity conditions. These isotherm data were used to determine adsorption and desorption kinetic constants at different temperatures. The figures below show breakthrough curves for CO₂ adsorption with respect to different inlet CO₂ concentrations of <400 ppm and the accompanying adsorption isotherm collected at 22 ℃.

The design of our DAC system includes a sorbent-washcoated monolith approach. The adsorption kinetic expression determined for a powdered form of a sorbent is applied to a sorbent-washcoated monolith block being operated under different flow conditions to validate a feasibility of the conceptual approach. Important adsorption isotherm and kinetic parameters determined from this model will enable us to scale up the DAC system by investigating the overall CO₂ capture efficiency, volumetric productivity, and throughput for a successful development of our DAC system.