Effect of packing size on packed bubble column hydrodynamics

Abstract

The present article focuses on the hydrodynamics of gas-liquid flow through a packed bubble column (PBC) reactor. Typically used in heterogeneously catalyzed gas-liquid reactions, such reactors employ a stationary packing of solid particles (catalyst) through which gas and liquid phases flow concurrently upwards. Designing the reactor to operate in a regime where the overall reaction rate is independent of mixing and mass transfer phenomena is crucial, and an important part of the design is the choice of the packing particle size, DP. It is well known that liquid-solid mass transfer and intraparticle (void) diffusion limitations drive the choice of the largest acceptable mean particle diameter. In the present work, we provide a condition for smallest acceptable mean particle size based on the consideration of gas-liquid mass transfer. Using experiments in a 10” diameter PBC apparatus and computational fluid dynamics (CFD) simulations, we demonstrate that this condition is related to a balance between bubble buoyancy and surface tension and is given by DP>Kσ/β2ρlg with K≈1.6 and β≈0.84.