Influence of gas distributor design on the oxygen transfer characteristics of an airlift fermenter

Bovonsombut, Sittisin; Wilhelm, Anne‐Marie; Riba, J. P.

doi:10.1002/jctb.280400303

Cited by 11 publications

(5 citation statements)

References 24 publications

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“…Ohkawa et al17 found the opposite trend to be true in terms of pore size, while Wongsuchoto et al16 found pore number to have a negligible effect. In contrast, Bovonsombut et al10 found that k L a increases up to superficial gas velocities of 0.0042 m/s, and decreases at higher gas velocities.…”

Section: Previous Workmentioning

confidence: 85%

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Gas transfer and liquid dispersion inside a deep airlift reactor

Giovannettone¹,

Gulliver²

2008

AIChE Journal

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in Wiley InterScience (www.interscience.wiley.com).Gas transfer experiments in bubbly flow are conducted inside a deep bubble column/ airlift reactor containing air and water with a maximum aerated water height of 23.4 m and diameter of 1.06 m. The effects of geometry and operating conditions on mixing and gas transfer are determined. Fluorescence measurements are used to estimate dispersion coefficients for several operating conditions, while bubble-water gas transfer measurements are made using dissolved oxygen (DO) probes. A two-phase convection-dispersion model is fit to the DO measurements using the liquid film coefficient (k L ) as a fitting parameter. Sparger differences had a substantial effect upon k L , and the gas transfer coefficient for the airlift reactor was four times that of the bubble column. Results are characterized using Sherwood, Reynolds, and Bond numbers. A low Reynolds number exponent was found, indicating that k L in a deep column tends toward a constant and is not highly dependent upon air discharge.

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Section: Previous Workmentioning

confidence: 85%

“…Higher k L a values occur at higher gas flow rates 3–5, 9–16. Many of these studies have shown the relationship to be almost linear, although Alvarez‐Cuenca et al3 found this to be true only for a limited range of gas velocities.…”

Section: Previous Workmentioning

confidence: 99%

Gas transfer and liquid dispersion inside a deep airlift reactor

Giovannettone¹,

Gulliver²

2008

AIChE Journal

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“…First, the effect of the cross-sectional area ratio of down-comer to riser had been shown to have a strong influence on the circulation velocity. ,, The shape of the different section was also known to affect the performance of airlift reactors, especially in EL-ALR, which enables the use of wider range of geometry for each section . In contrast, most investigators have shown that the gas sparger, which was of important in conventional bubble columns, , had little influence on the hydrodynamics in airlift reactors. , No information about the effect of the junction zone and disengagement zone geometry on the local and global performance of EL-ALR was available in the literature.…”

Section: Introductionmentioning

confidence: 99%

“…19 In contrast, most investigators have shown that the gas sparger, which was of important in conventional bubble columns, 20,21 had little influence on the hydrodynamics in airlift reactors. 22,23 No information about the effect of the junction zone and disengagement zone geometry on the local and global performance of EL-ALR was available in the literature.…”

Section: Introductionmentioning

confidence: 99%

Experimental and Numerical Simulation for Gas−Liquid Phases Flow Structure in an External-Loop Airlift Reactor

Chen

Dong

Guo

2007

Ind. Eng. Chem. Res.

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A gas−liquid external-loop airlift reactor with a riser 0.47 m in diameter and 2.5 m in height and two external-loop down-comers 0.08 m in diameter and 2.5 m in height were used to investigate the gas−liquid two-phase flow structure. Local phase holdups were measured simultaneously by a microconductivity probe with air as the gas phase and water as the liquid phase over a wide range of operation conditions. Liquid flow velocity measurements were performed using the electrolyte tracer measurement (ETM) technique. The hydrodynamics near the sparger zone, riser disengagement zone (zone 1), junction zone (zone 2), and down-comer disengagement zone (zone 3) were systematically examined using the CFDs at the local scale and at the riser scale, respectively. The simulation results showed that zones 1, 2, and 3 exhibit three different flow regimes, which were the secondary mixed flow regime, the mixed flow regime, and the homogeneous bubble regime, respectively. It was also indicated that turbulent kinetic energy and turbulent kinetic energy dissipation rate were influenced by a gas sparger. These results were necessary to explain these different regimes using computational fluid dynamics (CFD) to provide deeper insight at the local scale for reactor geometry, such as gas sparger, junction and disengagement zones as well as the gas−liquid phase flow microstructure. The simulation results at the local scale were difficult to obtain by experiment. The numerical simulating results of local gas holdup and local gas and liquid velocities agreed well with the experimental data at a low gas flow rate. However, large errors occurred in the simulations at a high gas flow rate, because of poor estimation of the influence of bubble-induced turbulence or the higher density of the tracer and the poor mesh refinement. The flow structure and turbulence parameters of the phases presented here were useful for designing gas−liquid external-loop airlift reactors.

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“…26 The synergistic effect of sparger design and coalescence inhibitors (aqueous solutions of inorganic salts) on the hydrodynamics of an EL-ALR was described in the research of Snape et al 27 The reason for suppression of the distributor's effect was ascribed to the influence of superposed liquid flow on the two-phase flow pattern and bubble rise velocity in the riser. 27 Bovonsombut et al 28 concluded that k L a could become 2 or 3 times higher in a DT-ALR with the porous plate in comparison to the perforated ring sparger if inorganic salts were added to the liquid−phase. On the other hand, organic compounds brought a decrease in k L a for both distributors used, as the coefficient k L decreased to a greater extent in comparison to a slight enhancement of the specific area a.…”

Section: Introductionmentioning

confidence: 99%

Sparger Type Influence on the Volumetric Mass Transfer Coefficient in the Draft Tube Airlift Reactor with Diluted Alcohol Solutions

Šijački

Tokic

Kojić

et al. 2013

Ind. Eng. Chem. Res.

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In this work, the influence of addition of normal aliphatic alcohols (from methanol to n-octanol) and the gas sparger type (single orifice, perforated plate, and sinter plate) on the volumetric mass transfer coefficient in a draft tube airlift reactor was investigated. The results showed that the addition of alcohols from methanol to n-hexanol led to an increase in the volumetric mass transfer coefficient, in comparison to water, while n-heptanol and n-octanol had the opposite effect. The influence of the gas sparger was dominant at low superficial gas velocities. At higher gas velocities, the liquid-phaseproperties and the sparger type, being opposite in effect on mass transfer, annulled one another's influence. Also, simple correlation was proposed to predict the volumetric mass transfer coefficient. The analysis of the parameters in the proposed correlation showed that the liquid-phaseproperties, expressed through the surface tension gradient, and the gas sparger type, mainly through initial bubble size, had a marked influence on the mass transfer.

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Influence of gas distributor design on the oxygen transfer characteristics of an airlift fermenter

Abstract: The performances of two types of gas distributor (a perforated ring and a porous plate) in an airlift

Cited by 11 publications

References 24 publications

Gas transfer and liquid dispersion inside a deep airlift reactor

Gas transfer and liquid dispersion inside a deep airlift reactor

Experimental and Numerical Simulation for Gas−Liquid Phases Flow Structure in an External-Loop Airlift Reactor

Sparger Type Influence on the Volumetric Mass Transfer Coefficient in the Draft Tube Airlift Reactor with Diluted Alcohol Solutions

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