Axial liquid mixing in high‐pressure bubble columns

Abstract

Axial dispersion coefficients of the liquid phase in bubble columns

Two-Phase Bubble Columns: A Comprehensive Review

“…The presence of "non-coalescence induced" and "coalescence induced" bubbles has been investigated by different authors (i.e., [17][18][19]46] Bubble columns may run batchwise (or, with U L < 0.01 m/s), in co-current or in counter-current mode [1][2][3]. Low liquid velocities generally do not affect ε G -as found by several investigators [24,47,[113][114][115][116][117][118][119]-because, if U L is low compared to the bubble rise velocities, the acceleration of the bubbles (caused by the non-stagnant operation) will be negligible [120]. For example, Akita and Yoshida [47] reported a negligible effect of liquid velocities up to 0.04 m/s, either in gas-liquid counter-current or con-current operations.…”

Comprehensive experimental investigation of counter-current bubble column hydrodynamics: Holdup, flow regime transition, bubble size distributions and local flow properties

“…Low liquid velocities do not affect the holdup-as found by several investigators (Akita and Yoshida, 1973;de Bruijn et al, 1988;Lau et al, 2004;Rollbusch et al, 2015a;Sangnimnuan et al, 1984;Shah et al, 1982;Shawaqfeh, 2003;Voigt and Schügerl, 1979;Yang and Fan, 2003)-because, if U L is low compared with the bubble rise velocities, the acceleration of the bubbles is negligible (Hills, 1976). For example, Akita and Yoshida (1973) (d c ¼0.152 m, H c ¼2.5 m) observed a negligible effect of U L (up to 0.04 m/s) in both co-current and countercurrent operations.…”

Bubble column reactors for high pressures and high temperatures operation

“…In this regime breakage and coalescence phenomenon control the flow which is usually not controlled by the primary bubble at the gas distributor (Kantarci et al, 2005). The first heterogeneous regime (also called "churn-turbulent" regime) is characterized by the existence of a liquid macro-circulation due to the non homogeneous radial profile of gas distribution: the liquid is rising in the centre of the column and is getting down near the wall (Forret et al, 2003;Kantarci et al, 2005;Smith et al, 1996;Xue et al, 2008;Yang and Fan, 2003;Zahradník et al, 1997). This movement is the main cause of turbulence in the heterogeneous flow.…”

“…Many studies are operated in semi-batch mode (batch for liquid, continuous for gas phase) and only few studies deals with continuous mode (see above). The degree of mixing in bubble columns is rarely studied and the determination of liquid or gas axial dispersion coefficient is rarely performed ( Wilkinson et al, 1993;Yang and Fan, 2003;Zahradník et al, 1997). The main objective of this review is to find the relevant parameters for the design of WAO processes and to provide bases for operating bubble columns in continuous mode at high pressures and temperatures.…”