Gas holdup, bubble behaviour, and mass transfer characteristics in a two‐stage internal loop airlift reactor with different screens

Zhang, Xiaobo; Guo, Kai; Qi, Wenzhe; Zhang, Ting; Liu, Chunjiang

doi:10.1002/cjce.22767

Cited by 33 publications

(20 citation statements)

References 40 publications

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“…Therefore, various high-efficient ILALRs were developed from the perspective of increasing the gas holdup. 10 − 13 The hydrodynamics of the ILALRs have been studied mainly via experiment 12 , 14 − 19 and computational fluid dynamics (CFD) simulation. 20 − 27 In the experimental studies, gas holdup, mixing time, bubble size, residence time distribution, and liquid circulating velocity can be measured by invasive 7 or non-invasive methods.…”

Section: Introductionmentioning

confidence: 99%

Computational Fluid Dynamics Simulation of Hydrodynamics in a Two-Stage Internal Loop Airlift Reactor with Contraction-Expansion Guide Vane

et al. 2021

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Global circulation and liquid back mixing adversely affect the continuous production of a multistage internal airlift loop reactor. A contraction-expansion guide vane (CEGV) is proposed and combined with a two-stage internal loop airlift reactor (TSILALR) to suppress the liquid back mixing between stages. A computational fluid dynamics (CFD) simulation is conducted to evaluate the performance of the CEGV in the TSILALR. The bubble size distribution and turbulent flow properties in the TSILALR are considered in the CFD simulation by using the population balance model and RNG k - ε turbulence model. The CFD model is validated against the experimental results. The deviations in the gas holdup and mean bubble diameter between the simulation and experimental results are less than 8% and 6%, respectively. The streamlines, flow pattern, bubble size distribution, and axial liquid velocity in the TSILALRs with and without the CEGV at superficial velocities of 0.04 and 0.08 m/s are obtained by CFD simulation. It has been shown that the CEGV generated local circulation flows at each stage instead of a global circulation flow in the TSILALR. The average global gas holdup in the TSILALR with a CEGV increased up to 1.98 times. The global gas holdup increased from 0.045 to 0.101 and the average axial velocity in the riser decreased from 0.314 to 0.241 m/s when the width of the CEGV increased from 50 to 75 mm at the superficial gas velocity of 0.08 m/s.

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Section: Introductionmentioning

confidence: 99%

Computational Fluid Dynamics Simulation of Hydrodynamics in a Two-Stage Internal Loop Airlift Reactor with Contraction-Expansion Guide Vane

et al. 2021

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“…A mass transfer enhancement can be safely realized by increasing the gas-liquid interfacial area. For example, by adding internals [18][19][20][21] or changing operation conditions, [22][23][24] the bubble diameter can be effectively decreased, and thus the interfacial area increased. Alcohols, 25,26 surfactants 8,[27][28][29] and electrolytes [30][31][32] are typically added in coalescence systems to inhibit bubble coalescence 33 and increase bubble rigidity, 34 by which bubbles become smaller and a larger interfacial area is obtained.…”

Section: Introductionmentioning

confidence: 99%

Effects of bubble size on the gas–liquid mass transfer of bubble swarms with Sauter mean diameters of 0.38–4.88 mm in a co‐current upflow bubble column

Wang

Guo

Liu

et al. 2020

J of Chemical Tech & Biotech

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BACKGROUND: Bubble columns have found a wide range of application in biochemical industry. Mass transfer in the bubble column can be manipulated by adjusting the bubble size. Thus, for the design of bubble columns, it is necessary to investigate the behaviors of different-sized bubbles. This work attempts to study the global hydrodynamic and mass transfer characteristics of bubble swarms with Sauter mean diameters (d 32) of 0.38-4.88 mm, from microbubbles to millimeter-sized bubbles, in a co-current bubble column. RESULTS: The specific interfacial areas of the bubble swarms with d 32 of 0.38-1.47 (generated by ceramic membrane module) and 1.05-4.88 mm (generated by plate gas distributor) are 250-1100 and 7-270 m −1 , respectively. The liquid-side mass transfer coefficient (k L) of those two kinds of bubbles are (0.45-1.16) × 10 −4 and (0.58-7.65) × 10 −4 m s −1 , respectively. CONCLUSION: Decreasing the bubble size can effectively increase the volumetric mass transfer coefficient (k L a), especially when the bubble size decreases to several micrometers. The major contribution to the mass transfer enhancement results from the increase of the specific interfacial area. Conversely, the k L decreases clearly. It is demonstrated that Higbieʼs and Frosslingʼs equations can approximate the k L of the bubble swarms with d 32 > 2 mm and d 32 < 2 mm in the bubble column, respectively.

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“…The bubble diameter was analyzed using ImageJ software. The bubble diameter for elliptical bubbles was measured by considering the major and minor axis of the bubble as :

true d_{normalB} = \sqrt[3]{d_{1}^{2} d_{2}}

…”

Section: Methodsmentioning

confidence: 99%

Effect of Surface Tension on Hydrodynamics and Mass Transfer Coefficient in Airlift Reactors

2020

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The hydrodynamics and volumetric mass transfer coefficient play important roles in the design and scale-up of airlift reactors. The effect of surface tension on hydrodynamics and volumetric mass transfer coefficient in internal loop airlift reactors was investigated. With reduction of the surface tension of the fluid, the hydrodynamic parameters raised, namely, gas phase holdup, flow regime transition point, and interfacial area, whereas the bubble diameter as well as the liquid velocity decreased and the volumetric mass transfer coefficient increased. Empirical correlations are proposed for gas-phase holdup and volumetric mass transfer coefficient in terms of dimensionless numbers and can be applied in the design of airlift reactors.

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Gas holdup, bubble behaviour, and mass transfer characteristics in a two‐stage internal loop airlift reactor with different screens

Cited by 33 publications

References 40 publications

Computational Fluid Dynamics Simulation of Hydrodynamics in a Two-Stage Internal Loop Airlift Reactor with Contraction-Expansion Guide Vane

Computational Fluid Dynamics Simulation of Hydrodynamics in a Two-Stage Internal Loop Airlift Reactor with Contraction-Expansion Guide Vane

Effects of bubble size on the gas–liquid mass transfer of bubble swarms with Sauter mean diameters of 0.38–4.88 mm in a co‐current upflow bubble column

Effect of Surface Tension on Hydrodynamics and Mass Transfer Coefficient in Airlift Reactors

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