Mixing and mass transfer characteristics of an unbaffled aerated agitation vessel with unsteadily forward-reverse rotating multiple impellers

摘要

Mixing and mass transfer characteristics of an unbaffled aerated agitation vessel with a liquid height-to-diameter ratio of 2 having unsteadily forward-reverse rotating multiple impellers, a cross type of impellers with four delta blades (CDs), were experimentally studied for air-water system in comparison with those of a baffled vessel having steadily unidirectionally rotating disk turbine impellers with six flat blades (DTs). For the forward-reverse rotating CD vessel, the contribution of sparged gas to enhancement in liquid phase mixing was observed in the entire range of gas sparging rate including its lower range. Agitating by the forward-reverse rotating CDs functioned effectively to enhance gas-liquid mass transfer not only in the lower range of gas sparging rate but also in its higher range. The features in operating the forward-reverse rotating multiple CD vessel were discussed in terms of the differences in the mixing time and volumetric mass transfer coefficient due to changes in the power input.