Effect of Superficial Gas Velocity on Bubble Size, Terminal Bubble Rise Velocity and Gas Hold‐up in Bubble Columns

Jamialahmadi, M.; Müuller-Steinhagen, H.

doi:10.1002/apj.5500010103

Cited by 26 publications

(12 citation statements)

References 36 publications

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“…as a small amount of surfactant is added to the water), further reductions in surface tension (higher alcohol concentrations) have a much smaller impact on k L a except for the case in which there is no rotation of the inner cylinder and for low gas flow rates. Previous studies in other flow geometries have also suggested that there is a limiting concentration when using ethanol to increase the mass transfer coefficient, above which the change in k L a becomes less pronounced [67]. Indeed, such an interpretation is consistent with the observation that neither the bubble diameter nor the values of k L a change significantly for the higher alcohol concentrations (lower surface tensions) considered.…”

Section: Volumetric Mass Transfer Coefficientsupporting

confidence: 83%

“…The mean of the bubble Sauter diameters varies between approximately 2.0-4.5 mm for most cases with standard deviations of 0.12-1.31 mm. Comparison of the mean bubble size for the non-rotating case with data obtained using a conventional bubble column [67] is shown in Fig. 6.…”

Section: Bubble Size and Shapementioning

confidence: 99%

“…Comparison of mean bubble diameter in non-rotating Taylor-Couette reactor with that of bubble column[67].…”

mentioning

confidence: 99%

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Experimental investigation of the effect of ethyl alcohol surfactant on oxygen mass transfer and bubble size distribution in an air-water multiphase Taylor-Couette vortex bioreactor

Ramezani

Legg

Haghighat

et al. 2017

Chemical Engineering Journal

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Volumetric liquid side mass transfer, bubble size distribution, and bubble shape was measured in a vertically oriented semi-batch gas-liquid Taylor-Couette vortex reactor with an aspect ratio of Γ=h/(r o -r i )=40 and radius ratio of η=r i /r o =0.75. Azimuthal Reynolds number, Axial Reynolds number and Capillary number were varied between 0 to 3.8×10 4 , 7 to 99, and 6.1×10 -6 to 76.0×10 -6 , respectively. Power-law correlations based on these data were presented for dimensionless Sauter mean diameter and Sherwood number in terms of the dimensionless parameters. Presence of ethanol as surfactant in the liquid was shown to inhibit bubble coalescence, which in addition to lowering interfacial surface tension causes a generally smaller bubble size at higher concentrations of surfactant. It was also shown that the mass transfer coefficient generally increases with higher concentrations of surfactant. Both the bubble diameter and mass transfer are influenced more at lower concentrations of surfactant, and the introduction of higher amount of ethanol causes a decrease in both parameters. Keywords Gas-liquid mass transfer, Surfactant, Sherwood number, Taylor-Couette vortex bioreactor.  The addition of surfactant decreases bubble size Nomenclature Roman a Specific gas-liquid interfacial surface area [m 2 /m 3 ] C Concentration [mg/L] d Bubble diameter [mm] D Diffusion coefficient [m 2 /s] E Ellipticity of spheroid g Gravitational acceleration [m/s 2 ] h Axial distance from the bottom of reactor [m] k Volumetric mass transfer coefficient [m/s] l Spheroid major diameter [m] m Spheroid minor diameter [m] N Impeller (inner cylinder) rotational speed [rev/s] Q Volumetric flow rate [L/min] r i Outer radius of the inner cylinder [m] r o Inner radius of the outer cylinder [m] u Superficial velocity [m/s] Greek Γ Reactor aspect ratio (Γ=h/(r o -r i )) ε G Gas holdup η Reactor radius ratio (η=r i /r o ) ω Rotational speed of the inner cylinder [rad/s]

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Section: Volumetric Mass Transfer Coefficientsupporting

confidence: 83%

Section: Bubble Size and Shapementioning

confidence: 99%

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Experimental investigation of the effect of ethyl alcohol surfactant on oxygen mass transfer and bubble size distribution in an air-water multiphase Taylor-Couette vortex bioreactor

Ramezani

Legg

Haghighat

et al. 2017

Chemical Engineering Journal

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“…Besides, it is often used to determine the flow regimes [14,16,25]. Two methods can be used to estimate the global gas holdup: height difference measurement [36] and differential pressure measurement [37][38][39][40]. With the height difference method, the global gas holdup is determined from the height of the unaerated liquid and the total height under aeration.…”

Section: Gas Holdupmentioning

confidence: 99%

Global characterization of hydrodynamics and gas-liquid mass transfer in a thin-gap bubble column intended for microalgae cultivation

Thobie

Gadoin

Blel

et al. 2017

Chemical Engineering and Processing: Process Intensification

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Global characterization of hydrodynamics and gas-liquid transfer in a 2D column with a 4 mm thickness is carried out with water and aqueous glycerol solutions. This new design can be used as a photobioreactor of low thickness to intensify the volumetric productivity by increasing microalgae concentration. To mimic the presence of algae cultures, the liquid viscosity is adjusted with glycerol. Focuses are made on flow regimes and their transitions, mixing, and gas-liquid transfer at the scale of the reactor. In comparison with conventional bubble columns lower terminal velocities are obtained. So, in homogeneous regime, the residence time of bubbles is greater than in conventional bubble columns and the gas holdup is slightly higher. However, regime transitions appear at relatively low superficial gas velocities in the confined bubble column. In addition, two transition regimes are visible and have macroscopic flow structures very similar to the ones observed for conventional columns. For the mixing time, a dependence on the viscosity is observed and whatever the solution tested, this parameter decreases very quickly with the increase of the gas superficial velocity. Finally, global gas-liquid mass transfer coefficients measurements show lower values than in classical bubble columns at the same superficial gas velocity.

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“…Most of the previous experimental investigations have concluded that the gas holdup in bubble columns is strongly dependent on the column geometry (i.e. length and diameter) 2–6. On the basis of the column geometry, the following three regions have been identified by many researchers:7 …”

Section: Introductionmentioning

confidence: 99%

Hydrodynamic investigation of bubble‐column reactors: effect of column configuration

Akhtar

Tadé

Pareek

2010

Asia-Pacific J Chem Eng

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Bubble-column reactors are quite popular in the chemical, biochemical and petrochemical industries due to their relatively simple construction, favourable heat and mass transfer properties and low operating cost. Among the various design parameters, column geometry (configuration) has a significant impact on the overall throughput. In this study, an experimental investigation of the bubble-column configuration on its hydrodynamics has been conducted with three different sizes of the column (ID = 10-45 cm). A comparison in terms of the overall gas holdup as well as localised bubble properties is performed using the four-point optical technique and hydrodynamic similarities/dissimilarities are discussed. The study showed that the overall gas holdup was a function of the gas flow rate. For the range of gas velocity investigated (9.5-22.3 cm 3 / min), the smaller column had 50-60% more holdup than the bigger column. Localised bubble properties exhibited similar behaviour (i.e. higher values for the smaller column). A comparative study of L/D illustrated an invariant behaviour at a high value of L/D (>5.5). A low L/D (≤1.5), however, showed a prominent influence on hydrodynamics. 

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Effect of Superficial Gas Velocity on Bubble Size, Terminal Bubble Rise Velocity and Gas Hold‐up in Bubble Columns

Cited by 26 publications

References 36 publications

Experimental investigation of the effect of ethyl alcohol surfactant on oxygen mass transfer and bubble size distribution in an air-water multiphase Taylor-Couette vortex bioreactor

Experimental investigation of the effect of ethyl alcohol surfactant on oxygen mass transfer and bubble size distribution in an air-water multiphase Taylor-Couette vortex bioreactor

Global characterization of hydrodynamics and gas-liquid mass transfer in a thin-gap bubble column intended for microalgae cultivation

Hydrodynamic investigation of bubble‐column reactors: effect of column configuration

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