Gas-Liquid Mass Transfer in Pulp Retention Towers

Authors

  • Vilas B. Rewatkar,

    1. Department of Chemical and Biological Engineering and Pulp and Paper Research Institute of Canada, Pulp and Paper Centre, The University of British Columbia, Vancouver, BC V6T 1Z4, Canada
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  • Chad P. J. Bennington

    Corresponding author
    1. Department of Chemical and Biological Engineering and Pulp and Paper Research Institute of Canada, Pulp and Paper Centre, The University of British Columbia, Vancouver, BC V6T 1Z4, Canada
    • Department of Chemical and Biological Engineering and Pulp and Paper Research Institute of Canada, Pulp and Paper Centre, The University of British Columbia, Vancouver, BC V6T 1Z4, Canada
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Abstract

The volumetric gas-liquid mass transfer rate, kLa, was measured under batch conditions in a 0.28 m diameter laboratory-scale retention column. Tests on water, and on unbleached kraft (UBK) pulp suspensions (mass fractions, Cm from 0.013 to 0.09) were made with air or nitrogen sparged through the column at superficial gas velocities between 0.0015 to 0.05 m/s. kLa varied with suspension mass concentration and superficial gas velocity, initially decreasing with increasing mass concentration, reaching a minimum between Cm = 0.03 and 0.06, and then increasing. The minimum in kLa coincided with a change in hydrodynamics within the column, from bubble column behaviour below Cm = 0.03 to porous solid behaviour above Cm = 0.06.

Abstract

On a mesuré le transfert de matière gaz-liquide volumétrique, kLa, dans des conditions discontinues dans une colonne de rétention à l'échelle de laboratoire de 0,28 m de diamètre. Des essais sur l'eau et sur des suspensions de pâte kraft non blanchie (UBK) (fractions volumiques, Cm, entre 0,013 et 0,09), ont été menés avec de l'air ou de l'azote aspergé dans la colonne à des vitesses de gaz superficielles variant entre 0,0015 et 0,05 m/s. kLa varie avec la concentration volumique de la suspension et la vitesse de gaz superficielle, diminuant au départ avec l'augmentation de la concentration volumique, atteignant un minimum à Cm = 0,03 et 0,06, puis augmentant. Le minimum pour kLa coincide avec un changement de l'hydrodynamique dans le colonne, passant d'un comportement de colonne à bulles sous Cm = 0,03 à un comportement solide poreux au-delà de Cm = 0,06.

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