Hydrodynamic characteristics and gas–liquid mass transfer in a biofilm airlift suspension reactor

Abstract

The hydrodynamics and mass transfer, specifically the effects of gas velocity and the presence and type of solids on the gas hold‐up and volumetric mass transfer coefficient, were studied on a lab‐scale airlift reactor with internal draft tube. Basalt particles and biofilm‐coated particles were used as solid phase. Three distinct flow regimes were observed with increasing gas flow rate. The influence of the solid phase on the hydrodynamics was a peculiar characteristic of the regimes. The volumetric mass transfer coefficient was found to decrease with increasing solid loading and particle size. This could be predominantly related to the influence that the solid has on gas hold‐up. The ratio between gas hold‐up and volumetric mass transfer coefficient was found to be independent of solid loading, size, or density, and it was proven that the presence of solids in airlift reactors lowers the number of gas bubbles without changing their size. To evaluate scale effects, experimental results were compared with theoretical and empirical models proposed for similar systems. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 60: 627–635, 1998.

CFD-accelerated bioreactor optimization: reducing the hydrodynamic parameter space

“…Conflicting results have been reported where increases in flow rate can either increase 45 or decrease 46 the mass transfer rate. Nicolella et al 47,48 discovered that mass transfer of biofilm-covered particles in airlift reactors is roughly 15% lower than that of clean particles.…”