A new type of anchor impeller with original baffles, the NX Mixer, has been developed that provides good liquid mixing over a wide viscosity range and good heat transfer at the vessel wall. To evaluate the performance of the NX Mixer, the mixing time was measured by the discoloration method and found to be shorted compared to other impellers. The solid-liquid mass transfer coefficients of solid particles
kL were measured by the electric conductivity method. The effect of power consumption per unit volume on the solid-liquid mass transfer was similar to that of the other large impellers.
kL of the NX Mixer was larger than that of other impellers when gas was sparged into the vessel. The gas-liquid mass transfer volumetric coefficient
kLa of NX Mixer was smaller than that of Rushton turbine impeller, because the gas hold-up of NX Mixer was smaller than that of Rushton turbine impeller. The observed mass transfer volumetric coefficients were correlated with a modified equation based on that of Hiraoka
et al. (2001). In addition, the average mass transfer coefficient
k and local mass transfer coefficient
k at the vessel wall were measured by using ion transfer in dilute solution. The local mass transfer coefficients of the NX Mixer were larger than those of other large impellers at the upper part through the lower part of the vessel wall, because the NX Mixer has a narrower clearance between the impeller and the vessel wall.
View full abstract