Characterization of a gas‐liquid OBC: Bubble size and gas holdup

Oliveira, Mónica; Ni, Xiongwei

doi:10.1002/aic.10282

Cited by 20 publications

(29 citation statements)

References 47 publications

(67 reference statements)

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“…An increase in the frequency leads to an increase in the k L a. The increase is small initially, but becomes more pronounced at higher oscillation frequencies, in accordance with the effect of oscillation on gas holdup [23]. The trends and magnitudes of k L a shown here are in accordance to previous mass transfer studies in OBCs [14,18,24].…”

Section: Resultssupporting

confidence: 79%

“…In summary, the overall mass transfer coefficient in the OBC increases significantly with both oscillation frequency and amplitude. This is a consequence of the highly turbulent flow pattern generated in the column as the oscillation increases, leading to frequent bubble breakage and a subsequent reduction in the Sauter mean diameter, as well as an increase in the residence time of the bubbles, when trapped in recirculating vortices [23].…”

Section: Resultsmentioning

confidence: 99%

“…To establish the relative importance of each of these factors, k L a was correlated as a function of Sauter mean diameter (D 32 ) and holdup (ε G ) measured experimentally [19,23] According to Eq. (6), the volumetric mass transfer coefficient is influenced by both an increase in the gas holdup, due to a prolonged residence time of the gas phase, and a decrease in the Sauter mean diameter.…”

Section: Resultsmentioning

confidence: 99%

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Effect of hydrodynamics on mass transfer in a gas–liquid oscillatory baffled column

Oliveira

2004

Chemical Engineering Journal

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In this paper, we present an experimental study on mass transfer of oxygen into water in an oscillatory baffled column (OBC). The objective of this work is to establish the contribution of individual parameters, such as the size of bubbles and the gas holdup, to the overall volumetric mass transfer coefficient (k L a). Our results show that the gas holdup is the most important factor. The liquid-side mass transfer coefficient (k L ) is calculated directly from the experimental measurements of gas holdup, Sauter mean diameter and k L a, and an increase of k L with D 32 is observed. The results also show that, above a critical level of fluid oscillation, the mass transfer coefficients are mainly governed by the oscillatory operating conditions, while independent of the type of gas sparger.

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Section: Resultssupporting

confidence: 79%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

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Effect of hydrodynamics on mass transfer in a gas–liquid oscillatory baffled column

Oliveira

2004

Chemical Engineering Journal

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“…This suggested the enhanced liquid mixing and higher velocity fluctuations on the gas-liquid interface reduced the boundary layer on the bubble's surface, as previously shown in similar studies. 27,31 In this study, it was found that K L a seems to vary linearly with Q gas and U G (Figure 8c). Other studies carried out in single-orifice OBCs of Oliveira and Ni, 27 Hewgill et al, 13 and Taslim and…”

Section: Flow Visualisation Of Liquid and Spatial Tracking Of Bubblesmentioning

confidence: 92%

CO₂ Dissolution and Design Aspects of a Multiorifice Oscillatory Baffled Column

Pereira

Sousa

Alves

et al. 2014

Ind. Eng. Chem. Res.

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Dissolution of CO 2 in water was studied for a batch vertical multiorifice baffled column (MOBC) with varying orifice diameters (d 0 ) of 6.4−30 mm and baffle open area (α) of 15−42%. Bubble size distributions (BSDs) and the overall volumetric CO 2 mass transfer coefficient (K L a) were experimentally evaluated for very low superficial gas velocities, U G of 0.12− 0.81 mm s −1 , using 5% v/v CO 2 in the inlet gas stream at a range of fluid oscillations (f = 0−10 Hz and x 0 = 0−10 mm). Remarkably, baffles presenting large d o = 30 mm and α = 36%, therefore in the range typically found for single-orifice oscillatory baffled columns, were outperformed with respect to BSD control and CO 2 dissolution by the other baffle designs or the same aerated column operating without baffles or fluid oscillations. Flow visualization and bubble tracking experiments also presented in this study established that a small d o of 10.5 mm combined with a small value of α = 15% generates sufficient, strong eddy mixing capable of generating and trapping an extremely large fraction of microbubbles in the MOBC. This resulted in increased interfacial area yielding K L a values up to 65 ± 12 h −1 in the range of the U G tested, representing up to 3-fold increase in the rate of CO 2 dissolution when compared to the unbaffled, steady column. In addition, a modified oscillatory Reynolds number, Re o ′ and Strouhal number, St′ were presented to assist on the design and scale-up of gas−liquid systems based on multiorifice oscillatory baffled columns. This work is relevant to gas−liquid or multiphase chemical and biological systems relying on efficient dissolution of gaseous compounds into a liquid medium.

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“…In general, dispersions are characterized by arithmetic mean bubble diameter or Sauter diameter [45]. The latter is defined as the mean diameter with the same ratio of volume to surface area as the entire ensemble [46].…”

Section: Two-phase Flowmentioning

confidence: 99%

Energy Optimization of Gas–Liquid Dispersion in Micronozzles Assisted by Design of Experiment

2017

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Abstract:In recent years gas-liquid flow in microchannels has drawn much attention in the research fields of analytics and applications, such as in oxidations or hydrogenations. Since surface forces are increasingly important on the small scale, bubble coalescence is detrimental and leads to Taylor bubble flow in microchannels with low surface-to-volume ratio. To overcome this limitation, we have investigated the gas-liquid flow through micronozzles and, specifically, the bubble breakup behind the nozzle. Two different regimes of bubble breakup are identified, laminar and turbulent. Turbulent bubble breakup is characterized by small daughter bubbles and narrow daughter bubble size distribution. Thus, high interfacial area is generated for increased mass and heat transfer. However, turbulent breakup mechanism is observed at high flow rates and increased pressure drops; hence, large energy input into the system is essential. In this work Design of Experiment assisted evaluation of turbulent bubbly flow redispersion is carried out to investigate the effect and significance of the nozzle's geometrical parameters regarding bubble breakup and pressure drop. Here, the hydraulic diameter and length of the nozzle show the largest impacts. Finally, factor optimization leads to an optimized nozzle geometry for bubble redispersion via a micronozzle regarding energy efficacy to attain a high interfacial area and surface-to-volume ratio with rather low energy input.

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Characterization of a gas‐liquid OBC: Bubble size and gas holdup

Abstract: A fundamental experimental study of gas-liquid contacting in an oscillatory

Cited by 20 publications

References 47 publications

Effect of hydrodynamics on mass transfer in a gas–liquid oscillatory baffled column

Effect of hydrodynamics on mass transfer in a gas–liquid oscillatory baffled column

CO₂ Dissolution and Design Aspects of a Multiorifice Oscillatory Baffled Column

Energy Optimization of Gas–Liquid Dispersion in Micronozzles Assisted by Design of Experiment

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Characterization of a gas‐liquid OBC: Bubble size and gas holdup

Abstract: A fundamental experimental study of gas-liquid contacting in an oscillatory

Cited by 20 publications

References 47 publications

Effect of hydrodynamics on mass transfer in a gas–liquid oscillatory baffled column

Effect of hydrodynamics on mass transfer in a gas–liquid oscillatory baffled column

CO2 Dissolution and Design Aspects of a Multiorifice Oscillatory Baffled Column

Energy Optimization of Gas–Liquid Dispersion in Micronozzles Assisted by Design of Experiment

Contact Info

Product

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CO₂ Dissolution and Design Aspects of a Multiorifice Oscillatory Baffled Column