Transition velocities and phase holdups at minimum fluidization in gas–liquid–solid systems

Authors

  • Donghyun Lee,

    1. Department of Chemical and Biological Engineering, University of British Columbia, 2216 Main Mall, Vancouver, BC V6T 1Z4, Canada
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  • Arturo Macchi,

    1. Department of Chemical and Biological Engineering, University of British Columbia, 2216 Main Mall, Vancouver, BC V6T 1Z4, Canada
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  • Norman Epstein,

    Corresponding author
    1. Department of Chemical and Biological Engineering, University of British Columbia, 2216 Main Mall, Vancouver, BC V6T 1Z4, Canada
    • Department of Chemical and Biological Engineering, University of British Columbia, 2216 Main Mall, Vancouver, BC V6T 1Z4, Canada
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  • John R. Grace

    1. Department of Chemical and Biological Engineering, University of British Columbia, 2216 Main Mall, Vancouver, BC V6T 1Z4, Canada
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Abstract

Hydrodynamic experiments were performed using a 127-mm diameter column with 3.2-mm porous alumina, 3.3-mm polymer blend, 5.5-mm polystyrene and 6.0-mm glass spheres, with water, aqueous glycerol solution and silicone oil as liquids, and air as the gas. The voidage at minimum fluidization fell initially to a minimum, then rose gradually with increasing superficial gas velocity, and was lower for three-phase systems than for corresponding two-phase (liquid–solid) fluidized beds. The compaction appears to be due to agitation by gas bubbles near the minimum liquid fluidization condition. The gas holdups agree reasonably well with the correlation of Yang et al. (1993). Curves of minimum liquid fluidization velocity, Ulmf, vs. superficial gas velocity, Ug always show Ulmf decreasing as Ug increases, initially in a concave-downward manner, but sometimes concave-upward.

Abstract

On a effectué des expériences hydrodynamiques au moyen d'une colonne de 127 mm de diamètre, avec des sphères d'alumine poreuse de 3, 2 mm, de mélange de polymères de 3, 3 mm, de polystyrène de 5, 5 mm et de verre de 6, 0 mm, et avec de l'eau, une solution aqueuse de glycérol et de l'huile de silicone comme liquides et de l'air comme gaz. Le degré de vide à une fluidisation minimale passe initialement à un minimum, puis augmente graduellement avec la Vitesse de gaz superficielle, et ce vide est plus petit pour les systèmes triphasiques que pour les lits fluidisés biphasiques (liquide–solides) correspondents. Le compactage semble ětre causé par l'agitation par les bulles de gaz près de la condition de fluidisation de liquide minimale. Les rétentions de gaz concordent raisonnablement bien avec la corrélation de Yang et al. (1993). Les courbes de vitesse de fluidisation de liquide minimale, Ulmf, par rapport a la vitesse de gaz superficielle, Ug, montrent toujours une valeur de Ulmf smanière concave-descendante, mais parfois de manière concave-ascendente.

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