A computational fluid dynamics MacroModel for the design of bed adsorbers

A new three-dimensional (3D) multiphase computational fluid dynamics (CFD) model for adsorption physics in packed beds of spherical beads is developed and validated. The model is constituted at a macroscopic scale that integrates new volumetric source terms in the multi-species gas transport and energy conservation equations. These new terms, for the first time, take into account the impact of pores adsorption occupation rate or gas loading. Transient 3D simulations are performed at an atmospheric pressure of about 1.02 bar for different CO2-He gas mixture feed-in compositions (100%, 50%, and 15% CO2). The 3D model validation is conducted through quantitative comparisons with experimental data from the literature for CO2 adsorption on porous Zeolite-13X beads in a cylindrical fixed-bed. Results demonstrate the new model's ability to accurately predict the breakthrough curves and the thermal front propagation inside the bed. Finally, the new CFD model is applied to investigate CO2 capture in a new 3D design of fixed-bed adsorbers of equivalent adsorbent material volume. The new design outperformed the reference cylindrical design, thanks to its new geometry with higher surface area. This allows to shorten the adsorption periods in pressure and temperature swing adsorption processes and, thus, increase the overall gas separation process productivity.