Airlift bioreactors: Analysis of local two‐phase hydrodynamics

Young, Mark A.; Carbonell, Ruben G.; Ollis, David F.

doi:10.1002/aic.690370311

Cited by 103 publications

(104 citation statements)

References 47 publications

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“…Only a few studies concerning the hydrodynamics of air lift reactors exist. This is partly due to the relative good performance of 1D models based on a mechanical energy balance and a drift flux model to couple the gas and liquid phase (see, e.g., Chisti et al 1998, Hsu & Duduković 1980, Young et al 1991. Due to the liquid flowing in the axial direction, the back mixing in the air lift reactors is small compared to that of the bubble column.…”

Section: Air Lift Reactorsmentioning

confidence: 99%

“…Few papers deal with the local hydrodynamics of the air lift reactor. Young et al (1991) used a hot wire to measure the liquid velocity and gamma densitometry and a resistivity probe to obtain the gas fraction distribution. They showed that the liquid axial velocity profile is much less flat than the profile of a turbulent single phase at the same Reynolds number.…”

Section: Air Lift Reactorsmentioning

confidence: 99%

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Gravity-Driven Bubbly Flows

Mudde

2005

Annu. Rev. Fluid Mech.

163

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■ Abstract Gravity-driven bubbly flows are a specific class of flows, where all action is provided by gravity. An industrial example is formed by the so-called bubble column: a vertical cylinder filled with liquid through which bubbles flow that are introduced at the bottom of the cylinder. On the bubble scale, gravity gives rise to buoyancy of individual bubbles. On larger scales, gravity acts on nonuniformities in the spatial bubble distribution present in the bubbly mixture. The gravity-induced flow and flow structures can increase the inhomogeneity of the bubble distribution, leading to a turbulent flow. In this flow, specific scales are identified: a large-scale circulation with the liquid flowing upward in the center of the column and downward close to the wall. On the intermediate scale there are vortical structures; eddies of liquid, with a size on the order of the diameter of the column, that stir the liquid and radially transport the bubbles. On the small scale there is the local stirring of the bubbles. We describe the ideas developed over time and identify some open questions. We discuss the experimental findings on the turbulence generated, the stability of the flow, axial dispersion, and the similarities between bubble columns and air lifts. Especially for higher gas fractions, many questions still lack accurate answers. The lateral lift force in bubble swarms and the structure of the turbulence in the bubbly mixture are important examples of inadequately understood physical phenomena, providing many challenges for fundamental and applied research on bubbly flows.

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Section: Air Lift Reactorsmentioning

confidence: 99%

Section: Air Lift Reactorsmentioning

confidence: 99%

Gravity-Driven Bubbly Flows

Mudde

2005

Annu. Rev. Fluid Mech.

163

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“…If there is no gas in the downcomer, a macroscopic mechanical energy balance on a control volume that extends from the top of the downcomer to the sparger in the riser leads to [3,7]:…”

Section: Gas-liquid Separator and Downcomermentioning

confidence: 99%

“…The K i values were adopted directly from Young et al [7] and Sµez et al [3]. Both the ªaccessoriesº and ªwall friction (f dc L dc /D dc )º terms in (16) are subject to some uncertainty.…”

Section: Gas-liquid Separator and Downcomermentioning

confidence: 99%

Gas-Lift Reactors for Rapid Reactions with Appreciable Gas Consumption

Roberts

Carbonell

Sáez

2000

Chem. Eng. Technol.

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Gas-lift reactors offer important advantages for a number of gas/liquid and gas/liquid/solid reactions. However, the design and operation of these reactors can be complex when there is a substantial change in the molar gas flow rate along the length of the reactor, e.g., when a gaseous reactant is converted into a liquid product. In this situation, there is a strong coupling between reactor hydrodynamics and reaction kinetics, which arises from the fact that the rate of liquid circulation through the reactor and the longitudinal profile of gas holdup in the riser are mutually dependent. Several one-dimensional models have been developed to describe kinetic/hydrodynamic coupling in gas-lift reactors. These models offer useful insights into the parameters that affect reactor performance. The models can also be used to explore different approaches to scale-up.

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“…Such results can be ascribed to the character of the bubble bed in the riser. In the`drift #ux modela (Young, Carbonell & Ollis, 1991), ; @R is the terminal velocity of a single bubble, assuming that bubbles do not interact, that is, each bubble moves independently and is not a!ected by the presence of other bubbles. However, Verlaan and Tramper (1987) reported that bubbles tended to aggregate in the center of the column as the solids loading increase.…”

Section: Application Of the Hydrodynamic Modelmentioning

confidence: 99%

Hydrodynamics of a three-phase external-loop airlift bioreactor

Freitas

Fialová

Zahradník

et al. 2000

Chemical Engineering Science

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The e!ect of the distributing plate ori"ce diameter, air#ow rate, solids loading and solids density on the hydrodynamic characteristics * gas holdup, circulation time and liquid velocity * of a three-phase external-loop airlift reactor was characterized. It was observed that the gas distributor has a small e!ect on riser gas holdup, circulation time and downcomer liquid velocity. On the contrary, the air#ow rate, solids loading and solids density signi"cantly a!ect the hydrodynamic characteristics of the external-loop airlift reactor. A previously described model was used to estimate simultaneously both the riser gas holdup and the downcomer linear liquid velocity. The model simulated with high-accuracy experimental data obtained with three di!erent distributing plate ori"ce diameters, two solids density and solids loading up to 30% (v/v).

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Airlift bioreactors: Analysis of local two‐phase hydrodynamics

Abstract: . Agreement between the predicted and measured values was typically within 10% for both cases.

Cited by 103 publications

References 47 publications

Gravity-Driven Bubbly Flows

Gravity-Driven Bubbly Flows

Gas-Lift Reactors for Rapid Reactions with Appreciable Gas Consumption

Hydrodynamics of a three-phase external-loop airlift bioreactor

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