Theoretical Prediction of Volumetric Mass Transfer Coefficient (k<sub>L</sub>a) for Designing an Aeration Tank
Keywords:Prediction method, volumetric mass transfer coefficient, interfacial area, liquid-side mass transfer coefficient, bubble diameter, bubble rising velocity.
The objective of this present paper is to propose a new theoretical prediction method of the volumetric mass transfer coefficient (kLa) occurring in a gas-liquid contactor based on the dissociation of the liquid-side mass transfer coefficient (kL) and the interfacial area (a). The calculated results have been compared with those obtained with the experimental process in a small-scale bubble column. Tap water was used as liquid phase and an elastic membrane with a single orifice as gas sparger. Only the dynamic bubble regime was considered in this work (ReOR= 1501000 and We = 0.0024). This study has clearly shown that, whatever the operating conditions under test, the generated bubble diameters (dB), bubble frequency (fB) and their associated rising velocities (UB) were the important parameters in order to predict, not only the values of kLa, but also the values of a and of kL. Moreover, these obtained results could provide a better understanding of the parameters which influence the oxygen transfer mechanism in the aeration process. By using the correlations to estimate these bubble hydrodynamics (dB and UB), it diminishes times for measuring the associated mass transfer parameters and also their experimental complexities and errors.
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