Rise velocity and gas—liquid mass transfer of a single large bubble in liquids and liquid—solid fluidized beds

Abstract

Models for describing the rise velocity of and gas—liquid mass transfer from a single spherical-cap (in three-dimensional systems) or circular-cap (in two-dimensional systems) bubble in liquids and liquid—solid media are presented. The model for the bubble rise velocity is based on a force balance on a single bubble accounting for the impaction force due to solid particles. The model satisfactorily predicts the bubble rise velocity in liquid systems and liquid—solid fluidized beds under intermediate and high bed expansion conditions. The mass transfer model, on the other hand, considers two different mechanisms: transfer through the bubble roof and through the bubble base. Mass transfer through the bubble base can be further divided into two cases depending on the operating conditions. The prediction for the overall gas—liquid mass transfer coefficient of a single bubble in liquids as well as in liquid—solid fluidized beds is reasonably good.