Gas-liquid mass transfer in a three-phase fluidized bed containing low density particles

Tang, Wen Tzung; Fan, Liang Shih

doi:10.1021/ie00097a020

Cited by 38 publications

(17 citation statements)

References 7 publications

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“…This may be because diffusion is blocked by the solid particles. This trend for k,a agrees with the model prediction, eqn (8), and the data in a bubble column with CMC containing polypropylene particles (p, = 940 kg It is seen from Fig. 7c, on the other hand, that the volumetric mass transfer coefficient in Airlift-2 with xanthan gum increased with increasing solids concentration.…”

Section: Volumetric Mass Transfer Coefficient K Asupporting

confidence: 86%

“…7c, on the other hand, that the volumetric mass transfer coefficient in Airlift-2 with xanthan gum increased with increasing solids concentration. This is inconsistent with the proposed model, eqn (8). Considering that the gas hold-up in xanthan gum decreased with $:, the presence of particles in the viscoelastic non-Newtonian fluid might increase interfacial turbulence, which affects the oxygen transfer rate, and as a result increase the volumetric mass transfer coefficient.…”

Section: Volumetric Mass Transfer Coefficient K Amentioning

confidence: 71%

See 1 more Smart Citation

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: Volumetric Mass Transfer Coefficient K Asupporting

confidence: 86%

Section: Volumetric Mass Transfer Coefficient K Amentioning

confidence: 71%

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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show abstract

“…3, and hence a decrease in a. Similar observations were reported by Sánchez et al (2005) as well as in other types of threephase systems with solids of 1-2.5 mm in diameter and densities slightly greater than the liquid (Freitas and Teixeira, 2001;Tang and Fan, 1990). The effect of liquid velocity on the experimental values of k L a is minor (less than 5%) over the range studied.…”

Section: Volumetric Gas-liquid Mass Transfer Coefficientsupporting

confidence: 87%

Oxygen transfer and hydrodynamics in three-phase inverse fluidized beds

Hamdad

Hashemi

Rossi

et al. 2007

Chemical Engineering Science

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“…Additional verification of the experimental results is performed by comparing the experimental result in the current study to literature data under similar air-water systems [19,[21][22][23][24][25][26][27][28]. Since there is limited literature data available for low L/D ratio conditions, only experimental results obtained at L/D ratio of 7.2 are used for comparison.…”

Section: Comparison To Literature Datamentioning

confidence: 92%

“…Model fitted with the consideration of gas holdup flushing and sensor delay Model fitted without the consideration of gas holdup flushing and sensor delay [26] (b) Porous Plate…”

Section: Time (Ms)mentioning

confidence: 99%