Flow Characteristics in Cocurrent Upflow Bubble Column Dispersed with Micro-Bubbles

The flow characteristics and decomposition performance in the cocurrent upflow bubble column dispersed with micro-bubbles were experimentally examined. A micro-bubble generator was installed at the bottom of the column, and for comparison the sintered glass gas sparger was set at the lower part of the column. When milli-bubbles coexist with dispersed micro-bubbles, micro-bubbles disappear. This is considered because micro-bubbles are absorbed into the wake of milli-bubbles. The volumetric mass transfer coefficient is higher for micro-bubbles than for milli-bubbles, but the mass transfer coefficient is much lower for the former than for the latter. The apparent decomposition rate constant strongly depends on the volumetric coefficient. When the volumetric coefficient is higher, the rate constant of micro-bubbles is higher than that of milli-bubbles.