Oxygen mass transfer in a high solids loading three-phase internal-loop airlift reactor

Abstract

Determinations of volumetric mass transfer coefficient were conducted in a three-phase internal-loop airlift reactor with an enlarged degassing zone. The effect of parameters such as the airflow rate (riser superficial gas velocities between 0.01 and 0.5 m/s), solids loading (up to 30%, v/v), solids density (1023 and 1048 kg/m 3) and the liquid-phase properties on k L a was studied. It was observed that the increase of the airflow rate and the introduction of ethanol enhanced the volumetric mass transfer coefficient in the system. On the contrary, the progressive introduction of solids and a small increase on solids density were responsible for the diminishing of the mass transfer rate. Correlations for the volumetric mass transfer coefficient with the riser superficial gas velocity and solids loading were determined for the two solids density and the two liquid-phases. A good agreement between experimental data and the calculated values was obtained.

Oxygen transfer in a gas–liquid system containing solids of varying oxygen affinity

“…Some systems show an enhanced k L a [3][4][5] and some systems measure a decreased k L a [6,7] relative to systems without particles. It is clear, however, that the effect of the particles on the system is a function of particle properties, vessel and impellor dimensions and arrangement and operating conditions [8,9].…”

Characteristics of three-phase internal loop airlift bioreactors with complete gas recirculation for non-Newtonian fluids

“…Hydrodynamics such as liquid circulation velocity, gas holdup and solid holdup and the gas-liquid volumetric mass transfer coefficient are the most important parameters used in assessing the above airlift bioreactors. Several investigators have experimentally studied hydrodynamics such as the liquid velocity in the riser and downcomer and/or the overall gas-liquid volumetric mass transfer of the three-phase internal loop airlift bioreactors for the Newtonian fluids [4][5][6][7][8]. Van Benthum et al [9][10][11] discussed the three regimes and hydrodynamic characteristics of the two-and three-phase airlift reactors they developed: the biofilm airlift suspension extension (BASE) reactor.…”

The effects of geometry and operational conditions on gas holdup, liquid circulation and mass transfer in an airlift reactor

“…Particularly in recent work, the performance of airlift reactors has been studied in terms of oxygen transfer capability for further utilization in fed-batch cultures (Gallindez-Mayer et al, 2001) and in cultivations with a pellet-type growing microorganism (Freitas and Teixeira, 2001). The latter authors mention that results in the literature for mass transfer in airlift reactors vary widely and are contradictory, since the reactors and experimental procedures are all different.…”