Estimation of Gas Holdup in Three-Phase Fluidized BedContaining Small or Low Density Particles[16pt/Centering/Boldface]<Space line><Space line>

Toshiro MIYAHARA [12pt/Centering]
Department of Applied Chemistry,[italic/9pt/Centering]
Faculty of Engineering,
Okayama University of Science,
1-1 Ridai-cho, Kita-ku, Okayama 700-0005, Japan<Space line><Space line><Space line>
A mechanistic model based on the drift line created by a spherical bubble passing through a liquid is developed topredict the gas holdup in gas-liquid-solid three-phase fluidized beds containing small or low-density particles.

In themodel development, the drift line calculated from stream function for the three-dimensional case is used to predict themean liquid rise path in the bubble street.

The gas holdup can be estimated from the mean bubble rise velocity

obtained by the sum of the following: the single bubble rise velocity, the mean liquid velocity calculated from the meanliquid path, the gas velocity in the bubble street, and the liquid velocity. Agreement between the calculated andmeasured values of gas holdup is fairly good using the correction factor.

Also agreement of the calculated values ofgas holdup with the measurements in the bubble column is good using a constant correction factor of around 0.7.
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Keywords: word1; word2; word3(font は抄録部と同じ / Size : 9 pt / 普通名詞の場合すべて小文字 / 固有名詞の場
合には先頭は大文字 / 最後のキーワードの後ろにピリオドを付す); word4.

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Introduction [10pt/Boldface][10pt] Gas-liquid-solid fluidized bed systems
have been widely applied to many biotechnologicalprocesses such as fermentation and aerobic
wastewater treatment in which very small particles
and/or light particles whose densities are very close to
those of the liquid media are contained. Previously,
however, most research was concerned withthree-phase fluidized beds of glass beads, alumina
particles, etc., of which the densities were more than2500 kg/m3 (Muroyama and Fan, 1984). One of themost important is the gas holdup necessary to predict
the interfacial area. Bhatia and Epstein (1974)
developed the generalized wake model. To estimate
the gas holdup using this model requires twounknown parameters which are quitedifficult toobtain experimentally: the ratio of the solids holdup
in thewake to that in the liquid-solid fluidized bed
region and the ratio of the wake volume to the bubble
volume for a multibubbles system. In calculations
using the wake model, a potential difficulty exists inthe estimation of the gas holdup for the model.
Therefore, many empirical correlations for the gas
holdup were proposed and the effect of particle sizeon the gas holdup was described (Muroyama and Fan,1984).
In the present study, apart from the generalizedwake model, we will propose a model based on thedrift line created by a bubble passing through aliquid; we call it the drift line model. From the drift
line model, the mean bubble rise velocity can becalculated.
Concerning this mean bubble rise

velocity, a new approach for the calculation of the gas
holdup is demonstrated for the study of thehydrodynamic characteristics of gas-liquid-solid
fluidized bed systems containing small or low density
particles.
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1. Theoretical Model [10pt/Boldface]
1.1 Mean liquid rise path created by a bubble passing
through a liquid [10pt]
As shown in Fig. 1 (Joshi and Shah, 1981), in a
bubble column, the upward liquid flow at the centerof the column and the downward flow near the wall,
namely the liquid circulation flow, can be found.

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岡山理科大学の所属が複数続く場合には、大学名及び住所の部分は、最後の所属にのみ記載して下さい。例えば、応用数学科と修士課程応用数学専攻の所属を続けて書く場合には、以下のようになります。
* Department of applied mathematics,
Faculty of Science,
1) Graduate School of Science,
Okayama University of Science,
1-1 Ridai-cho, Kita-ku, Okayama 700-0005, Japan