Oxygen mass transfer in bubble columns

The mass transfer of oxygen between air and water has been studied in a bubble column over wide ranges of liquid and gas velocity. An oxygen probe was used to map the steady-state liquid phase concentration of oxygen throughout the column. At any given point in the column, the oxygen concentration increased with gas velocity. Minima were observed in plots of concentration against liquid velocity. Two distinct absorption regions were observed. Close to the distributor the concentration decreased rapidly with height and volumetric mass transfer coefficients ranged from about 0.2 to 2.1 s−1. These high values were attributed to enhanced mass transfer due to turbulence induced by the liquid and gas jets in the grid region. In the bulk of the column, axial concentration gradients were much smaller and the mass transfer coefficients were up to two orders of magnitude lower than in the grid region.