Hydrodynamics in an Internal Loop Airlift Reactor with a Convergence-Divergence Draft Tube

Wei, Chaohai; Xie, Bo; Xiao, Hongliang

doi:10.1002/(sici)1521-4125(200001)23:1<38::aid-ceat38>3.0.co;2-l

“…Many researches have dealt with hydrodynamics and mass transfer in airlift reactors including two-phase and threephase systems [7±10]. In our previous study [11], hydrodynamics in an internal loop airlift reactor with a convergencedivergence draft tube was investigated. The objective of this work is to examine its volumetric mass transfer coefficient of oxygen (VMTCO).…”

Section: Introductionmentioning

confidence: 99%

Volumetric Mass Transfer Coefficient of Oxygen in An Internal Loop Airlift Reactor with a Convergence-Divergence Draft Tube

Wei

¹

,

Xie

²

,

Xiao

³

et al. 2000

Chem. Eng. Technol.

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Experimental measurements of hydrodynamics and the volumetric mass transfer coefficient of oxygen (VMTCO) in an internal loop airlift reactor with different types of draft tubes are reported for the two‐phase systems, air/water and air/carboxyl methyl cellulose (CMC) solution, and a three‐phase system, air/water/resin particle, respectively. The properties of convergence‐divergence draft tubes with three different structural parameters are compared with those of the conventional column draft tube. The results indicate that gas holdups in convergence‐divergence draft tubes are higher than those in conventional draft tubes, the volumetric mass transfer coefficient of oxygen increases with increasing superficial air flow rates. The convergence‐divergence draft tubes all show higher mass transfer capacity than the traditional ones. A 10% higher mass transfer coefficient is observed for the three structural parameters. In the air/CMC system, the volumetric mass transfer coefficient of oxygen decreases with increasing bulk viscosity, while in the three‐phase system VMTCO increases with the resin particle loading. The correlation equation of the volumetric mass transfer coefficient with the operating conditions and structural parameters is established.

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“…In this type of airlift bioreactors the draft tube contracts and expands as the name suggests with continuous renewal of gas-liquid interfacial area to promote mass transfer. Wei et al (1999) studied a three phase airlift bioreactors of air, water and resin. They reported an increase in both ε g and K L a by 8% and 10%, respectively as compared to the conventional draft tube bioreactors with a lower liquid circulation due to the geometry of the convergent divergent vessel.…”

Section: Fig27 the Eifbab; External Loop Inverse Fluidized Bed Airlift Bioreactormentioning

confidence: 99%

Mixing characteristics of draft tube airlift bioreactor using the electrical resistance tomography

Yakubu-Gumery¹

2021

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0

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In this work, mixing characteristics in terms of mixing time, hydrodynamics (liquid circulation velocity and gas hold up) and shear rate were performed in the downcomer of a draft tube airlift bioreactor with different geometries (i.e., Ad/Ar between 0.38 – 2.31 and bottom clearances between 0.003-0.00 m). Newtonian (water and 34.5% coalescing sugar solution) and on Newtonian (0.2% and 0.5% xanthan gum solutions) with different viscosities were used as the liquid phase. Compressed air was used as the gas phase which was introduced through cross and circular shaped sparger configurations at superficial velocities Ugr = 0.00165-0.00807 m/s. The combined effects of geometric parameters (Ad/Ar, bottom clearances), sparger configuration, and liquid viscosity on mixing characteristics have been presented. Results showed that the increase in superficial gas velocity (Ugr) corresponds to an increase in energy generated, and thus decreases in mixing time. However, the increase in Ugr corresponds to the increase in liquid circulation velocity, gas holdup and shear rate values. Moreover, bottom clearances and draft tube diameters show effects on flow resistance frictional losses which affect results of mixing parameters investigated. The influence of sparger configurations on mixing time and liquid circulation velocity is significant due to their effect on gas distribution. Mixing time decreased to about 40% in air-water media using the cross shaped sparger. Results obtained with cross shaped sparger showed even and uniform distribution of gas, which provided better mixing as compared to the circular shaped sparger configuration. However, the sparger configuration effect on shear rate is not as significant (about 20% reduction in shear rate values using the cross shaped sparger). The effect of fluid viscosity had a significant influence on both mixing times and circulation velocity, especially in the coalescing media of sugar and xanthan gum solutions. Results from this work will help to develop a clear pattern for operation and mixing that can help improving [sic] several industrial processes, especially the ones related to emerging fields of technology such as the biotechnology industry.

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“…In this type of airlift bioreactors the draft tube contracts and expands as the name suggests with continuous renewal of gas-liquid interfacial area to promote mass transfer. Wei et al (1999) studied a three phase airlift bioreactors of air, water and resin. They reported an increase in both ε g and K L a by 8% and 10%, respectively as compared to the conventional draft tube bioreactors with a lower liquid circulation due to the geometry of the convergent divergent vessel.…”

Section: Fig27 the Eifbab; External Loop Inverse Fluidized Bed Airlift Bioreactormentioning

confidence: 99%

Mixing characteristics of draft tube airlift bioreactor using the electrical resistance tomography

Yakubu-Gumery¹

2021

Preprint

0

View full text Add to dashboard Cite

In this work, mixing characteristics in terms of mixing time, hydrodynamics (liquid circulation velocity and gas hold up) and shear rate were performed in the downcomer of a draft tube airlift bioreactor with different geometries (i.e., Ad/Ar between 0.38 – 2.31 and bottom clearances between 0.003-0.00 m). Newtonian (water and 34.5% coalescing sugar solution) and on Newtonian (0.2% and 0.5% xanthan gum solutions) with different viscosities were used as the liquid phase. Compressed air was used as the gas phase which was introduced through cross and circular shaped sparger configurations at superficial velocities Ugr = 0.00165-0.00807 m/s. The combined effects of geometric parameters (Ad/Ar, bottom clearances), sparger configuration, and liquid viscosity on mixing characteristics have been presented. Results showed that the increase in superficial gas velocity (Ugr) corresponds to an increase in energy generated, and thus decreases in mixing time. However, the increase in Ugr corresponds to the increase in liquid circulation velocity, gas holdup and shear rate values. Moreover, bottom clearances and draft tube diameters show effects on flow resistance frictional losses which affect results of mixing parameters investigated. The influence of sparger configurations on mixing time and liquid circulation velocity is significant due to their effect on gas distribution. Mixing time decreased to about 40% in air-water media using the cross shaped sparger. Results obtained with cross shaped sparger showed even and uniform distribution of gas, which provided better mixing as compared to the circular shaped sparger configuration. However, the sparger configuration effect on shear rate is not as significant (about 20% reduction in shear rate values using the cross shaped sparger). The effect of fluid viscosity had a significant influence on both mixing times and circulation velocity, especially in the coalescing media of sugar and xanthan gum solutions. Results from this work will help to develop a clear pattern for operation and mixing that can help improving [sic] several industrial processes, especially the ones related to emerging fields of technology such as the biotechnology industry.

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Hydrodynamics in an Internal Loop Airlift Reactor with a Convergence-Divergence Draft Tube

Cited by 18 publications

References 7 publications

Volumetric Mass Transfer Coefficient of Oxygen in An Internal Loop Airlift Reactor with a Convergence-Divergence Draft Tube

Volumetric Mass Transfer Coefficient of Oxygen in An Internal Loop Airlift Reactor with a Convergence-Divergence Draft Tube

Mixing characteristics of draft tube airlift bioreactor using the electrical resistance tomography

Mixing characteristics of draft tube airlift bioreactor using the electrical resistance tomography

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