Quantifying the Impact of Intraparticle Convection within Fixed Beds Formed by Catalytic Particles with Low Macro-Porosities

Abstract

Computational fluid dynamics (CFD) modeling plays a pivotal role in optimizing fixed bed catalytic chemical reactors to enhance performance but must accurately capture the various length-and time-scales that underpin the complex particle−fluid interactions. Within catalytic particles, a range of pore sizes exist, with micro-pore scales enhancing the active surface area for increased reactivity and macro-pore scales enhancing intraparticle heat and mass transfer through intraparticle convection. Existing particle-resolved CFD models primarily approach such dual-scale particles with low intraparticle macro-porosities as purely solid. Consequently, intraparticle phenomena associated with intraparticle convection are neglected, and their impact in the full bed scale is not understood. This study presents a porous particle CFD model, whereby individual particles are defined through two distinct porosity terms, a macro-porosity term responsible for the particle's hydrodynamic profile and a micro-porosity term responsible for diffusion and reaction. By comparing the flow profiles through full beds formed by porous and solid particles, the impact of intraparticle convection on mass and heat transfer, as well as on diffusion and reaction, was investigated.