Gas Holdup and Flow Regimes in a Thin-Gap Bubble Column with Newtonian and Non-Newtonian Liquid Phase

The influence of confinement and rheological properties of the liquid phase on the gas holdup and flow regimes in a 2 mm gap bubble column intended as an intensified photobioreactor at high cell concentration is investigated. The results indicate that at a given superficial gas velocity (U-Gsup), the gas holdup is higher with viscous or non-Newtonian (nN) fluids than in water and also in a thin-gap column than in an unconfined one. This behavior increases when confinement ratio increases. Regime transitions occur at lower U-Gsup for nN fluids compared to water and for a thin-gap column compared to classical columns. This information constitutes a first step toward the identification of optimal operating conditions for efficient operation of microalgae culture.