Lattice Boltzmann modelling of unsteady-state 2D concentration profiles in adsorption bed

This study describes a lattice Boltzmann model (LBM) developed to simulate two-dimensional (2D) unsteady-state concentration profiles, including breakthrough curves, in a tubular column packed with adsorbents. The model using d3q19d3q19 (three dimensions and 19 speeds) lattice solves the 3D time-dependent convection–diffusion–adsorption equation for an ideal binary gaseous mixture assuming different velocity profiles in the column, including radially flat (plug flow) and non-uniform across the column's cross-section. The simulation results show significant concentration gradient across the cross-section depending upon the d/dpd/dp ratio. The model results corroborate the experimental measurements made in the adsorption bed that the concentration due to breakthrough may be larger near the wall than at the core of the column due to the relatively larger local velocity in the vicinity of the wall. The LBM results have significance from the perspective of the physical understanding of the concentration profiles prevalent in the adsorption bed as well as effective design of a large-scale column. The model results are validated with the analytical solution to 1D axial dispersion problem, and to a few simple flow problems, such as Poiseuille and Couette flows.