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Keywords:

  • mass transfer coefficient;
  • pulsed disc and doughnut column;
  • axial diffusion model;
  • enhancement factor;
  • effective diffusivity

Abstract

A study of the mass transfer performance for a pulsed disc and doughnut extraction column has been presented for a range of operating conditions. The mass transfer performance has been investigated for both directions of mass transfer. This study has examined the mass transfer coefficients which has incorporated the effects of back-mixing in the continuous phase. The effect of operating variables including pulsation intensity and dispersed and continuous phase velocities on volumetric overall mass transfer coefficient has been investigated. The experiments showed that mixer-settler, transition and emulsion regimes exist in the column depending on the pulse characteristics. In the present work, effective diffusivity is substituted for molecular diffusivity in the Gröber equation for estimation of overall mass transfer coefficients. The enhancement factor is determined experimentally and there from a single empirical correlation is derived for prediction of enhancement factor in terms of Reynolds number, holdup and Eötvös number for all operating regimes and each mass transfer direction. The experimental results are in very good agreement with the values calculated by the proposed equation. © 2011 Canadian Society for Chemical Engineering