Journal
CHEMICAL ENGINEERING SCIENCE
Volume 104, Issue -, Pages 32-43Publisher
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.ces.2013.08.044
Keywords
Bubble columns; Hydrodynamics; Mass transfer; Multiphase flow; Draft tube airlift
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Funding
- RHODIA, member of the SOLVAY Group
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One-dimensional modelling of global hydrodynamics and mass transfer is developed for an annulus sparged draft tube airlift reactor operating at high gas throughputs. In a first part, a specific closure law for the mean slip velocity of bubbles in the riser is proposed according for, in one hand, the collective effects on bubble rise velocity and, in the other hand, the size of the liquid recirculation in the airlift riser. This global hydrodynamics model is found to well explain the global gas volume fraction measurements in the airlift riser for a wide range of superficial gas velocity (0.6 < J(G) < 10 cm s(-1)). In a second part, mass transfer in the airlift has been studied by using the gassing-out method and a dual-tip optical probe to measure the bubble size distributions. As for bubble columns, in such airlift, the volumetric mass transfer coefficient appears to be quite proportional to the gas superficial velocity. Finally, as in Colombet et al. (2011), mass transfer at the bubble scale seems to be weakly influenced by an increase of gas volume fraction. (C) 2013 Elsevier Ltd. All rights reserved.
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