The influence of vessel height and top‐section size on the hydrodynamic characteristics of airlift fermentors

Russell, Alan D.; Thomas, Carelle; Lilly, M. D.

doi:10.1002/bit.260430110

Cited by 59 publications

(71 citation statements)

References 10 publications

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“…In contrast to Siegel and Merchuk 10 and Merchuk et al, 11 Chisti and Moo-Young, 12 Russel et al, 15 and Lu et al 16 did not observe a signi®cant effect of the liquid height in the separator (H T ) on the liquid circulation and the gas holdup. According to these workers, H T would have a certain in¯uence only in the case of its low value.…”

Section: Gas-liquid Separatorcontrasting

confidence: 48%

“…According to these workers, H T would have a certain in¯uence only in the case of its low value. Russel et al 15 observed the existence of two zones in the separator, where the liquid passed predominantly through the lower part. When the level of liquid exceeded this zone, the gas holdup in the downcomer as well as the circulation velocity did not change any more (at constant air¯ow rate).…”

Section: Gas-liquid Separatormentioning

confidence: 98%

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Effect of a gas–liquid separator on the hydrodynamics and circulation flow regimes in internal‐loop airlift reactors

Klein

Godó

Dolgoš

et al. 2001

J of Chemical Tech & Biotech

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The role of the gas±liquid separator on hydrodynamic characteristics in an internal-loop airlift reactor (ALR) was investigated. Both gas holdup and liquid velocity were measured in a 30 dm 3 airlift reactor with two different head con®gurations: with and without an enlarged separator. A magnetic tracer method using a neutrally buoyant magnetic particle as¯owfollower was used to measure the liquid velocity in all sections of the internal-loop airlift reactor. Average liquid circulation velocities in the main parts of the ALR were compared for both reactor con®gurations. At low air¯ow rates the separator had no in¯uence on gas holdup, circulation velocity and intensity of turbulence in the downcomer and separator. At higher super®cial air velocities, however, the separator design had a decisive effect on the hydrodynamic parameters in the downcomer and the separator. On the other hand, the gas holdup in the riser was only slightly in¯uenced by the separator con®guration in the whole range of air¯ow. Circulation¯ow regimes, characterising the behaviour of bubbles in the downcomer, were identi®ed and the effect of the separator on these regimes was assessed. # 2001 Society of Chemical Industry Keywords: airlift reactor; separator; circulation regimes; circulation velocity;¯owfollower

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Section: Gas-liquid Separatorcontrasting

confidence: 48%

Section: Gas-liquid Separatormentioning

confidence: 98%

Effect of a gas–liquid separator on the hydrodynamics and circulation flow regimes in internal‐loop airlift reactors

Klein

Godó

Dolgoš

et al. 2001

J of Chemical Tech & Biotech

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“…The gas holdup in the separator is very close to the mean gas holdup in the whole reactor (61), as long as the top clearance C t is relatively small (one or two diameters). For larger top clearances, the behavior of the gas separator begins to resemble that of a BC, and the overall performance of the reactor is influenced by this change.…”

Section: Gas Holdupmentioning

confidence: 90%

“…It is quite common to enlarge the separator section to reduce the liquid velocity and to facilitate better disengagement of spent bubbles. Experiments have been reported in which the liquid level in the gas separator was high enough to be represented as two mixed vessels in series (51,61). Fresh gas may also be entrapped from the headspace if the fluid is very turbulent near the interface.…”

Section: Flow Configurationmentioning

confidence: 99%

Bioreactors: Airlift Reactors

Merchuk

Camacho

2010

Encyclopedia of Industrial Biotechnology

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ALRs are popular in modern bioprocess research and development and, in many cases, they have found industrial uses. The distinctive characteristics of ALRs are conferred by the fluid dynamics of the liquid‐gas or liquid gas‐solid mixtures: holdup, liquid velocity, and mixing in the riser, gas separator, and downcomer. Only a correct understanding of the interconnection of these regions can make possible the scale‐up of a laboratory device, to pilot or industrial size. Several correlations are available in the literature for the prediction of the fluid dynamic characteristics of the reactor and of the mass and heat transfer coefficients, and a selection is presented in this review. Significant progress has been made in the application of modern computational tools to the simulation and design of ALRs. In parallel, innovative and sophisticated methods have been applied to obtain a deeper insight into the mechanisms of fluid motion and the flow patterns in the reactor. However, no single research group has managed to cover all the variables over a wide range. The engineer confronting scale‐up or de novo design of an ALR must analyze the validity of the correlations and computation methods used for the calculations.

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“…They also proposed a dimensionless correlation for gas hold-up. Russel et al [6] investigated the effect of vessel height and top section size of an internal recirculation airlift reactor on the hydrodynamic characteristics. They found that the vessel height has a negligible effect on gas hold-up but the size of the top section was found to affect significantly liquid mixing and that an optimum size could be achieved.…”

Section: Introductionmentioning

confidence: 99%

Mass transfer studies in pneumatic reactors

et al. 1996

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Local mass transfer studies have been carried out in an external loop airlift reactor and indicated the existence of significant non-uniformities in aeration capacity in the various sections of the reactor. The traditional assumption of a single well mixed unit with a single kL a value for external loop airlift reactors was found to be poor and cannot represent adequately the reactor as a whole. The liquid head in the gadliquid separator was found to have a significant negative effect on the local mass transfer coefficient kL a. Visualization of flow patterns showed the existence of strong vortices in the riser and downcomer which contributed to a reduction in local aeration capacity. Mass transfer experiments in an aerated tank showed that the aeration capacity can be reduced by half in viscous media but improved significantly in the presence of salts.

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The influence of vessel height and top‐section size on the hydrodynamic characteristics of airlift fermentors

Cited by 59 publications

References 10 publications

Effect of a gas–liquid separator on the hydrodynamics and circulation flow regimes in internal‐loop airlift reactors

Effect of a gas–liquid separator on the hydrodynamics and circulation flow regimes in internal‐loop airlift reactors

Bioreactors: Airlift Reactors

Mass transfer studies in pneumatic reactors

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