Effect of liquid viscosity on mixing times in bubble columns

Abstract

Mixing is a key parameter in bioreactors studies as it can intensify mass and heat transfer and can affect biological reactions. In the present work, mixing times are investigated in a 42 L vessel with water and various polyethylene glycol and carboxymethyl cellulose solutions. To improve the physical description of dispersion induced by bubbles, the first step of our study was to characterize dispersion of tracers inside bubbly flows at various gas volume fractions for different liquid viscosities. A colorimetric technique is used in order to record mixing times corresponding to 95 or 80% of homogeneity. Bubble size is also measured at the same time by image processing. It clearly appears that the liquid viscosity impacts the mixing time value, the bubble size and the tracer propagation.