Mixing and mass transfer in tall bubble columns

In cocurrent bubble columns (15 and 20 cm diameter, 440 and 723 cm high) with different gas distributors measurements were carried out with tap water and solutions of salts and molasses. A stationary and a transient method were applied to determine the dispersion coefficients. Absorption and desorption of oxygen was studied by measuring the concentration profiles of oxygen in the liquid phase. Liquid phase mass transfer rates k_La were obtained adjusting the experimental profiles with the predictions of the axial dispersed plug flow model. Owing to the different gas spargers the k_La values of both columns differ by a factor of about two. Correlations are proposed for the k_La data of the various liquid phases which only depend on the gas velocity.