Interfacial mass transfer and axial liquid dispersion in aerated column bioreactors

Abstract

The upscaling of gas–liquid mass transfer and bioreaction in aerated cultures was performed within the volume averaging theory. Effective transport equations, including their associated closure problems, were derived for 1) the main substrates and biomass (non-transferable components), and 2) the gaseous substrate (transferable component). For the transferable component, two approaches were applied: 2a) the local mass equilibrium (one equation), and 2b) the two-fluid model (two equations). The nature of the dispersion tensors in the three averaged models is discussed. Numerical computations of the axial dispersion coefficient and the volumetric mass transfer coefficient were performed by solving the associated closure problems in unit cells (0.1 ≤ Re ≤ 300; 1 ≤ Sc ≤ 550; 0.1 ≤ Pe ≤ 300; Mo = 2.5 × 1011; 0.001 ≤ εG ≤ 0.05). The results of both parameters agree with trends reported in literature; some differences in orders of magnitude for DLzz are attributable to the mismatch between the experimental conditions and the occurrence of mesoscale interactions undetected in the computational cells.