Hold‐up and axial mixing characteristics of two and three phase fluidized beds

Kim, S. D.; Baker, C. G. J.; Bergougnou, M.A.

doi:10.1002/cjce.5450500603

Cited by 91 publications

(42 citation statements)

References 14 publications

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“…2 shows a typical result found in this study for the effect of the gas superficial velocity on the gas holdup at different static water levels. This result agrees well with reported investigations on similar systems [13,[16][17][18][19][20][21][22][23].…”

Section: Resultssupporting

confidence: 95%

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A Simple Approach to Measuring the Gas Phase Heat and Mass Transfer Coefficients in a Bubble Column

Daous

Al-Zahrani

2006

Chem Eng & Technol

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A simple experimental approach was developed to measure the gas phase volumetric heat and mass transfer coefficients in a bubble column and a slurry bubble column employing a single gas nozzle. The experimental technique was based on a transfer model that simulates humidification and direct contact evaporation models in the case of a gas bubble rising in a liquid of uniform temperature. The temperature and relative humidity of the inlet and outlet gas in the column are the only measurements required in this technique. Experiments were carried out in a 0.15 m inner diameter column using water as the liquid phase, air as the gas phase, and cation resins of 0.1 mm diameter and a specific gravity of 1.2, as the solid phase. The results showed that, when using solid concentrations in the range of 7-10 wt %, both the volumetric gas-phase heat and mass transfer coefficients increased with an increase in the gas superficial velocity and were further enhanced by increasing the solid load after a certain minimum superficial velocity had been reached in the column (0.044 m/s in the system used). Increasing the solid load beyond 10 wt %, did not contribute to a further increase in these coefficients. Furthermore, the gas holdup in the column increased with the superficial gas velocity and was further enhanced when the solid-phase load was in the range of 7-10 wt %. These observations agree well with previously reported findings by other investigators.

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Section: Resultssupporting

confidence: 95%

“…These authors have further shown that the use of a single nozzle helps to obtain fine and almost mono-sized bubbles. It has also been well established that the gas holdup increases with increasing gas rate [13,[16][17][18][19][20][21][22][23].…”

Section: Introductionmentioning

confidence: 99%

A Simple Approach to Measuring the Gas Phase Heat and Mass Transfer Coefficients in a Bubble Column

Daous

Al-Zahrani

2006

Chem Eng & Technol

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“…For bubble columns and slurry bubble columns, gas holdup has been found to increase with increasing superficial gas velocity (Kim et al, 1972;Koide et al, 1984;Fan et ai. 1987;Saxena et al, 1989Saxena et al, , 1990a.…”

Section: Effeets Of Gas Veloeitymentioning

confidence: 99%

“…Kitano and Fan (1988) -imperfect tracer puise method (Ostergaard and Michelsen, 1969) -continuous injection of colored tracer (Kim et al, 1972) -pulse of saline tracer (Kim and Kim, 1983;Morooka et al, 1986) antinuous injection of saline tracer (El-Temtamy et al, 1979) The axial dispersion coefficient is obtained fiom the residence time distribution data as measured with these techniques. Kim and Kim, 1983 Ostergaard and Michelsen ( 1969) found that the beds of 0.25 and 1.0 mm particles were chanicterized by a high degree of backmixing while beds of 6 mm glas beads were characterized by very low degree of backmixing.…”

Section: -34 the Ratio Of Wake Volume To Bubble Volumementioning

confidence: 99%

Heat Transfer and Hydrodynamics in a Three-Phase Slurry Bubble Column

Prakash

1997

Ind. Eng. Chem. Res.

103

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The instantaneous and time-averaged heat transfer coefficients in the regions near the wall and at the center and average gas holdups were measured in a 0.28 m diameter slurry bubble column for the air−water and air−water−glass beads (35 μm) system. The effects of high gas velocities (up to 0.35 m/s) and high solids concentrations (up to 40 vol %) were investigated. Gas holdup decreased with increasing slurry concentrations; the rate of decline was rapid at high gas velocities. The instantaneous local heat transfer measurements were analyzed to study the bubble behavior in the regions near the wall and at the center for different solids concentrations. Larger bubbles were detected in the wall region in slurry systems compared to the solid-free system. The average heat transfer coefficient decreased with increasing slurry concentrations. The heat transfer coefficient was always lower at the wall than at the center.

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“…The kLa, a and kL data of the present and previous where the units of Ug and Ut, dp, kLa and a are cm/s, (db<1mm) which behave as rigid spheres, kLa is proportional to Sc2 '3 13) Since kL is strongly influenced by the velocity of liquid elements and eddies, kL can be represented by kL = {ScY(Repy (12) where Sc and Rep are Schmidt and particle Reynolds numbers, respectively. The particle Reynolds number has been related to the energy dissipation rate in the beds based on Kolmogoroff's local isotropic turbulence theory.20'21}…”

Section: Correlations Of Datamentioning

confidence: 70%