(628d) Adsorption Kinetic Model for Direct Air Capture | AIChE

(628d) Adsorption Kinetic Model for Direct Air Capture


Akinjide, J. - Presenter, University of Cincinnati
Priye, A., Univeristy of Cincinnati
Lee, J. Y., University of Cincinnati
A large portion of CO2 in ~5.2 gigatons (Gt) is released in relatively small quantities from distributed sources emitted each year in the U.S. Therefore, for such emissions, point source CO2 capture is not feasible and direct air capture is an indispensable part of a diversified portfolio of technologies to mitigate U.S. greenhouse gas emissions. Successful direct air capture (DAC) technologies are required to separate high purity CO2 (e.g., >95%) with high selectivity toward CO2, low regeneration energy requirements, minimum chemical and thermal degradation, reliability, long lifetime, etc.

Adsorption kinetic model plays a key role in designing DAC systems. In this study, an adsorption kinetic model for our CO2 sorbent has been studied for DAC potential by integrating CO2 adsorption kinetics with a flow model. The mass transfer of CO2 in the porous sorbent bed can be modeled by solving the convection-diffusion equation within the porous sorbent. Intraparticle diffusion of CO2 inside the sorbent is modeled with adsorption kinetics. CO2 adsorption isotherm data is obtained for 400 ppm CO2 in ambient air at temperatures up to 40 °C and relative humidity using chemisorption. The model will couple the adsorption kinetics with external and intraparticle diffusion.

After the model result is validated with lab-scale experimental data, the model is used to investigate the direct effects of system parameters on the overall CO2 capture efficiency and flow throughput for the design of a DAC system. Currently, the sorbent is to be washcoated onto monolith to be installed inside the DAC system. This model predictions will provide the key design information on overall CO2 capture efficiency, volumetric productivity, and throughput in terms of dimensions of monoliths including pitch sizes.