Homogeneous–heterogeneous regime transition in bubble columns

Růžička, Marek C.; Zahradník, Jindřich; Drahoš, J.; Thomas, N. H.

doi:10.1016/s0009-2509(01)00116-6

Cited by 186 publications

(159 citation statements)

References 47 publications

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“…Regardless of the gas input into the bubble column, this distributor produces poly-dispersed bubble size distribution with presence of small and large bubbles [37,38] which is characteristic for pure heterogeneous regime. The monotonous dependence of gas hold-up on gas superficial velocity seen in Figure 3 is typical for a bubble column operated in pure heterogeneous regime [32,33]. According to these criteria, our column is out of the aspect ratio independent operation mode.…”

Section: Description Of Hydrodynamicsmentioning

confidence: 73%

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Measurement of Volumetric Mass Transfer Coefficient in Bubble Columns

et al. 2018

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Abstract:The paper presents a brief overview of experiments on volumetric mass transfer coefficient in bubble columns. The available experimental data published are often incomparable due to the different type of gas distributor and different operating conditions used by various authors. Moreover, the value of the coefficient obtained experimentally is very sensitive to the particular method and to the physical models used in its evaluation. It follows that the Dynamic Pressure Method (DPM) is able to provide physically correct values not only in lab-scale contactors but also in pilot-scale reactors. However, the method was not correctly proven in bubble columns. In present experiments, DPM was employed in a laboratory-scale bubble column with a coalescent phase and tested in the pure heterogeneous flow regime. The method was successfully validated by the measurements under two different conditions relevant to the mass transfer. First, the ideal pressure step was compared with the non-ideal pressure step. Second, the pure oxygen absorption was compared with the simultaneous oxygen-and-nitrogen absorption. The obtained results proved that DPM is suitable for measuring the mass transport in bubble columns and to provide reliable data of volumetric mass transfer coefficient.

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Section: Description Of Hydrodynamicsmentioning

confidence: 73%

“…The gas distributor was a perforated metal plate with free plate area of 0.2% and orifices 1.6 mm in diameter which produces pure heterogeneous regime for the whole range of gas flow rate investigated [32,33]. All experiments were performed in batch mode with 1 m of clear liquid height.…”

Section: Methodsmentioning

confidence: 99%

Measurement of Volumetric Mass Transfer Coefficient in Bubble Columns

et al. 2018

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“…For example, using a "fine sparger" (d 0 < 1 mm, such as for porous spargers, membranes, needles, sieve tray/perforated plates with small openings) the homogeneous flow regime is stabilized (Mudde et al, 2009) and a "pure-homogeneous" flow regime exists, which leads to the hindrance effect that physically is manifested by the peak on the gas holdup graph. In contrast, using a "coarse sparger" (d 0 > 1 mm) the "pure-homogeneous" flow regime may not exist and a "pseudo-homogeneous" flow regime is observed at lower gas superficial velocities; finally, when using a "very coarse sparger" (d 0 > > 1 mm), the homogeneous flow regime may not be established and a "pure heterogeneous flow regime" takes place (Ruzicka et al, 2001).…”

Section: Bubble Column Fluid Dynamicsmentioning

confidence: 97%

The dual effect of viscosity on bubble column hydrodynamics

Besagni

Inzoli

Guido

et al. 2017

Chemical Engineering Science

112

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A B S T R A C TSome authors, in the last decades, have observed the dual effect of viscosity on gas holdup and flow regime transition in small-diameter and small-scale bubble columns. This work concerns the experimental investigation of the dual effect of viscosity on gas holdup and flow regime transition as well as bubble size distributions in a large-diameter and large-scale bubble column. The bubble column is 5.3 m in height, has an inner diameter of 0.24 m, and can be operated with gas superficial velocities in the range of 0.004-0.20 m/s. Air was used as the dispersed phase, and various water-monoethylene glycol solutions were employed as the liquid phase. The water-monoethylene glycol solutions that were tested correspond to a viscosity between 0.9 mPa s and 7.97 mPa s, a density between 997.086 kg/m 3 and 1094.801 kg/m 3 , a surface tension between 0.0715 N/m and 0.0502 N/m, and log 10 (Mo) between −10.77 and −6.55 (where Mo is the Morton number). Gas holdup measurements were used to investigate the global fluid dynamics and the flow regime transition between the homogeneous flow regime and the transition flow regime. An image analysis method was used to investigate the bubble size distributions and shapes for different gas superficial velocities, for different solutions of watermonoethylene glycol. In addition, based on the experimental data from the image analysis, a correlation between the bubble equivalent diameter and the bubble aspect ratio was proposed. The dual effect of viscosity, previously verified in smaller bubble columns, was confirmed not only with respect to the gas holdup and flow regime transition, but also for the bubble size distributions. Low viscosities stabilize the homogeneous flow regime and increase the gas holdup, and are characterized by a larger number of small bubbles. Conversely, higher viscosities destabilize the homogeneous flow regime and decrease the gas holdup, and the bubble size distribution moves toward large bubbles. The experimental results suggest that the stabilization/destabilization of the homogeneous regime is related to the changes in the bubble size distributions and a simple approach, based on the lift force, was proposed to explain this relationship. Finally, the experimental results were compared to the dual effect of organic compounds and inorganic compounds: future studies should propose a comprehensive theory to explain all the dual effects observed.

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“…Note that the mean bubble velocity u relates to the bubble retention time t by u = H/t, where H is the column height, giving a linear relation e ∼ t. The regime transition has been studied and several models suggested, e.g. [5] and references therein. Despite these efforts, many basic questions about the effect of important operational parameters and the system properties on the transition remain unanswered.…”

Section: Introductionmentioning

confidence: 99%

Effect of viscosity on homogeneous–heterogeneous flow regime transition in bubble columns

Růžička

2003

Chemical Engineering Journal

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Experiments were performed in a cylindrical 0.14 m diameter bubble column with a metal perforated plate. Air and aqueous solutions of glycerol with viscosity 1-22 mPa s were the phases. Gas holdup was measured and plotted against the gas flow rate. The critical point where the homogeneous-heterogeneous regime transition begins was determined by the drift-flux plot of the primary data. The homogeneous regime stability was expressed by the critical values of the gas holdup and gas flow rate. The results show that moderate viscosity (3-22 mPa s) destabilizes the homogeneous regime and advance the transition. The results indicate that low viscosity (1-3 mPa s) could stabilize the homogeneous regime. The destabilizing effect of the column height proved previously for air-water system applies also to viscous batches.

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Homogeneous–heterogeneous regime transition in bubble columns

Cited by 186 publications

References 47 publications

Measurement of Volumetric Mass Transfer Coefficient in Bubble Columns

Measurement of Volumetric Mass Transfer Coefficient in Bubble Columns

The dual effect of viscosity on bubble column hydrodynamics

Effect of viscosity on homogeneous–heterogeneous flow regime transition in bubble columns

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