Mass transfer from oscillating bubbles in bubble column reactors

In spite of the amount of work on bubble columns, their design and scale up is still a difficult task due to the lack of understanding of the mass transfer mechanisms. In this work we have studied the contribution of bubble deformation to the mass transfer rate for the air-water system from a theoretical point of view. The specific contact area is obtained using a population balance model. A new scheme for bubble classes has been implemented to account for the effect of bubble oscillations in mass transfer due to coalescence and break-up processes. Meanwhile, a theoretical model for the Sherwood number for oscillating bubbles in inviscid fluids has been used to implement the effect of bubble deformation on the liquid-film resistance. Coupling the population balance with the Sherwood number for oscillation bubbles, k(L)a values are predicted. It was found that bubble oscillations explain the wide range of parameters often used to fit k(L) and the fact that in bubble columns the concentration profiles surrounding individual bubbles are not completely developed due to the presence of other bubbles, in agreement with previous results from the literature. (C) 2009 Elsevier B.V. All rights reserved.