Particle-resolved computational fluid dynamics modeling of coupled heat and mass transfer in fixed-bed adsorbers

Abstract

Fixed-bed adsorbers are simulated at full particle-scale resolution to predict the coupled evolution of gas-mixture flow dynamics, mass transfer, adsorption kinetics, and heat effects during CO2 capture. A porous-based, direct-forcing immersed boundary method is developed and implemented in the open-source Computational Fluid Dynamics platform OpenFOAM to resolve interstitial flow and transport within a realistically packed bed while avoiding body-fitted meshing around individual pellets. The model is applied to a cylindrical adsorbing bed containing roughly 5000 spherical Zeolite-13X beads of diameter dp=1.5 mm. This representation reflects a realistic adsorber segment under industrially relevant operating conditions. The model is applied to adsorption from a binary CO2/He mixture (50%/50%) at atmospheric pressure with an initial temperature of 295 K and a maximum temperature rise up to around 350 K due to adsorption-induced thermal effects, and it is validated by comparing predicted breakthrough behavior and thermally coupled front dynamics against experimental data from the literature. In addition to reproducing outlet composition histories, the particle-resolved framework provides space- and time-resolved fields of velocity, concentration, and temperature, enabling mechanistic quantification of channeling, wall effects, and the synchronization between mass and thermal fronts. The proposed approach offers a validated high-fidelity reference for developing improved closures and reduced-order models for pressure and temperature swing adsorption cycles design and energy-efficient adsorber/heat-management optimization.