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Radial liquid velocity distribution in an external-loop airlift column with a tapered riser

Authors

  • Mikio Ka Wagoe,

    Corresponding author
    1. Department of Chemical Engineering, Nara National College of Technology, 22 Yata-machi, Yamato-Koriyama, Nara 639-1080, Japan
    • Department of Chemical Engineering, Nara National College of Technology, 22 Yata-machi, Yamato-Koriyama, Nara 639-1080, Japan
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  • Shohei Yoshida,

    1. Department of Chemical Engineering, Nara National College of Technology, 22 Yata-machi, Yamato-Koriyama, Nara 639-1080, Japan
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  • Yukimasa Ishii,

    1. Department of Chemical Engineering, Nara National College of Technology, 22 Yata-machi, Yamato-Koriyama, Nara 639-1080, Japan
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  • Kazvmitsu Naoe

    1. Department of Chemical Engineering, Nara National College of Technology, 22 Yata-machi, Yamato-Koriyama, Nara 639-1080, Japan
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Abstract

Radial and axial liquid velocity distributions in the tapered riser were investigated theoretically and experimentally. The liquid velocity distributions were computed by solving the Navier-Stokes equation numerically based on a modified mixing-length theory. Both radial and axial components of liquid velocity were taken into account. As a result, we found that the radial velocity component was much smaller than the axial velocity component. For a cylindrical column, which means no tapered section, a simplified solution was obtained. The simplified solution was found to agree well with the rigorous numerical solution even in the tapered riser. To confirm the validity of the present hydrodynamic model, the velocity distributions in the tapered riser were measured by an electric probe method using KCl solution as a tracer. The measured velocity distributions agreed with the computed ones, except in the vicinity of the bottom of the tapered riser at high gas flow rates.

Abstract

On a ètudiè de manieáre thèorique et expèrimentale les distributions de vitesse radiale et axiale du liquide dans une colonne montante conique. Les distributions de vitesse du liquide ont ètè calculèes par ordinateur en rèsolvant numèriquement l'èquation de Navier-Stokes d'apreás une thèorie de longueur de mèlange modifièe. Les deux composantes radiale et axiale de la vitesse du liquide ont ètè prises en considèration. Comme consèquence, nous avons trouvè que la composante de vitesse radiale ètait beaucoup plus petite que la composante de vitesse axiale. Pour une colonne cylindrique, c'est-à-dire sans section conique, on a obtenu une solution simplifièe. On a trouvè que cette solution simplifièe concordait bien avec la solution numèrique rigoureuse měme dans la colonne montante conique. Afin de confirmer la validitè du prèsent modeále hydrodynamique, les distributions de vitesse dans la colonne montante conique ont ètè mesurèes au moyen d'une sonde èlectrique et d'une solution de KO comme traceur. Les distributions de vitesse mesurèes concordent avec les distributions calculèes par ordinateur, exceptè dans le voisinage du fond de la colonne montante conique à de forts dèbits de gaz.

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