Heat transfer in three-phase fluidized beds containing low-density particles

Kumar, Samir; Kusakabe, Ken Takeshi; Fan, Liang Shih

doi:10.1016/0009-2509(93)81062-z

Cited by 12 publications

(4 citation statements)

References 13 publications

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“…Solid particles in bioprocesses usually have sizes ranging from 200 pm to 3 mm and densities ranging from 1020 to 1300 kg m-3. 10 Bioreactor operation was batchwise with respect to liquid phase. Known quantities of liquid and solid phases formed the batch through which air was passed continuously.…”

Section: Methodsmentioning

confidence: 99%

Gas Hold‐Up and Oxygen Transfer in Three‐Phase External‐Loop Airlift Bioreactors: Non‐Newtonian Fermentation Broths

Kawase¹,

Hashimoto²

1996

J. Chem. Technol. Biotechnol.

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The effects of solids loading on gas hold-up and oxygen transfer in external-loop airlift bioreactors with non-Newtonian fermentation media are discussed. Experiments were performed in two model external-loop airlift bioreactors with aqueous solutions of carboxymethyl cellulose (CMC) and xanthan gum representing non-Newtonian flows. Low-density plastic particles of 1030 and 1300 kg m-3 were used and the solids loading was varied in the range 0-20% (v/v). For the inelastic non-Newtonian CMC aqueous solutions, the presence of low-density solid particles slightly increased the riser gas hold-up, &gr, but decreased the volumetric mass transfer coefficient, k,a. On the other hand, #gr decreased but k,a increased with solids loading in the viscoelastic non-Newtonian xanthan gum aqueous solution. The extent of these effects depended on non-Newtonian flow behavior. Theoretical models of riser gas hold-up and volumetric mass transfer coefficient have been developed. The capability of the proposed models was examined using the present experimental data obtained in the model external-loop airlift bioreactors and the available data in the literature. The data were successfully correlated by the proposed correlations except the results for k,a coefficient in the xanthan gum solution.Key words: three-phase external-loop airlift bioreactor, non-Newtonian fermentation broths, gas hold-up, volumetric mass transfer coefficient. a A d Ar C CAL D Dd D r EXP 9 Hd kI. NOTATION Specific surface area (m-') Downcomer cross-sectional area (m2) Riser cross-sectional area (m2) Coefficient Calculated Diffusivity (m2 s -l ) Downcomer diameter (m) Riser diameter (m) Experimental Gravitational acceleration (m s -2, Length of vertical portion of downcomer (m) Liquid-phase mass transfer coefficient (m s -') K R n Usgr V L 3 & PI P S PI 0 z +v * To whom correspondence should be addressed. 325 Consistency index in a power-law model (Pa s") Effective consistency index in a power-law model for (solid-non-Newtonian liquid) two-phase system (eqn (2)) (Pa s") Flow index in a power-law model Superficial gas velocity in the riser (m s -l ) Liquid volume (m3) Shear rate (SKI) Energy dissipation rate per unit mass (W kg-') Liquid density (kg m-3) Solid density (kg m-3) Effective density of (solid-liquid) two-phase system (eqn (2)) (kg m-3) Surface tension (N m-') Shear stress (Pa) Riser gas hold-up J . Chem. Tech. Biotechnol. 0268-2575/96/$09.00 0 1996 SCI. Printed in Great Britain

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Section: Methodsmentioning

confidence: 99%

Gas Hold‐Up and Oxygen Transfer in Three‐Phase External‐Loop Airlift Bioreactors: Non‐Newtonian Fermentation Broths

Kawase¹,

Hashimoto²

1996

J. Chem. Technol. Biotechnol.

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“…The most effective method for the assessment of mimimum bubbling conditions has proven to be the analysis of the time-series of the bed-wire heat-transfer coefficient. It has Ž been suggested Kumar et al, 1993;Boerefijn et al, 1996, . 1999 that fluctuations of h are related to particle motion rather than to turbulence intrinsic to the fluid, even under dense bed fluidization conditions and regardless of how large is the contribution to h by fluid convection.…”

Section: Assessment Of the Onset Of The Bubbling Regimementioning

confidence: 98%

Fluidization of solids with CO₂ at pressures from ambient to supercritical

Marzocchella

2000

AIChE Journal

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“…Also, isothermal operation is assumed. Although this is a generally accepted condition, because of the low velocity of most biological reactions and because the mild operation temperatures cause no limitation in heat transfer, the process taking place is very complex, as a consequence of the interaction between gas, liquid, and solid phases (Kumar et al, 1993;Kim and Laurent, 1991;Fan, 1989), and should be taken into consideration especially in the case of large-scale bioreactors. Finally, the description that follows concentrates mainly in the liquid phase and solid biocatalytic particles, and some examples of how to treat a compound present in the gas phase, as oxygen, are also considered.…”

Section: Developing a Model For A Fluidized-bedmentioning

confidence: 99%

Fluidized‐Bed Bioreactors

Gòdia

Solà

1995

Biotechnology Progress

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Fluidized-bed reactors present a number of advantages that make them an attractive alternative in processes involving biocatalysts. However, fluidized-bed bioreactors are also realtively complex, basically for two reasons. First, their use requires the biocatalyst, commonly cells or enzymes, to be immobilized into or onto a solid support. Second, the hydrodynamic characterization is difficult, especially in those systems where three phases (gas-liquid-solid) are involved. The mathematical model of a fluidized-bed bioreactor needs to take into account those hydrodynamic aspects that will determine the flux model in the reactor. Moreover, the description of other aspects is also required: the mechanisms of transport between the different phases, the kinetic equations for the phenomena taking place in the biocatalytic particles, such as cell growth, product formation, substrate consumption, enzyme deactivation, and the mass balance equations in the reactor. In addition to these aspects, the application of fluidized-bed bioreactors to different kind of processes is also discussed. The potential of this type of bioreactor is also emphasized from the point of view of the different number of possible modifications in the design both of the bioreactor and the biocatalyst particles, in order to enhance its operation.

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Heat transfer in three-phase fluidized beds containing low-density particles

Cited by 12 publications

References 13 publications

Gas Hold‐Up and Oxygen Transfer in Three‐Phase External‐Loop Airlift Bioreactors: Non‐Newtonian Fermentation Broths

Gas Hold‐Up and Oxygen Transfer in Three‐Phase External‐Loop Airlift Bioreactors: Non‐Newtonian Fermentation Broths

Fluidization of solids with CO₂ at pressures from ambient to supercritical

Fluidized‐Bed Bioreactors

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Heat transfer in three-phase fluidized beds containing low-density particles

Cited by 12 publications

References 13 publications

Gas Hold‐Up and Oxygen Transfer in Three‐Phase External‐Loop Airlift Bioreactors: Non‐Newtonian Fermentation Broths

Gas Hold‐Up and Oxygen Transfer in Three‐Phase External‐Loop Airlift Bioreactors: Non‐Newtonian Fermentation Broths

Fluidization of solids with CO2 at pressures from ambient to supercritical

Fluidized‐Bed Bioreactors

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Fluidization of solids with CO₂ at pressures from ambient to supercritical