Influences of the Particle-Stacking Structure on the Turbulent Mass Transfer Process in Fixed Beds: Numerical Studies on RTD and Adsorption Using a Multiscale Strategy

Precise prediction and control of the mass transfer process in fixed beds are essential for their exact design and optimization in chemical engineering. However, the nonuniform particle-stacking structure introduces nonlinear characteristics in turbulent diffusion and mass transfer rate. Consequently, classical porous media-computational mass transfer (PM-CMT) models, which rely on empirical correlations and oversimplify the effects of the particle-stacking structure, often fail to accurately simulate mass transfer processes. To address this challenge, this study proposes a multiscale strategy to numerically investigate a turbulent mass transfer process in fixed beds. The multiscale strategy includes two steps: (1) elucidating the effects of different tube-to-particle diameter ratios (N) and particle shapes on turbulent diffusion using the recently developed particle resolved-computational mass transfer (PR-CMT) model; and (2) calculating the structure-based mass transfer rate coefficient from the particle-scale PR-CMT simulations and incorporating them into the structure-based PM-CMT framework for an adsorber-scale simulation. By application of this strategy, the nonlinear effects of particle-stacking structures on mass transfer are fully considered. As a result, the adsorber-scale simulation achieves better agreement with experimental data, with an average relative error of 7.93%, which is 38.82% and 10.55% lower than those of the classical PM-CMT models. This multiscale strategy offers a valuable approach for eliminating uncertainty over turbulent diffusion and mass transfer rates, providing a more reliable foundation for the design and optimization of fixed beds.