화학공학소재연구정보센터
Chemical Engineering & Technology, Vol.25, No.7, 723-727, 2002
Gas dispersion in rheologically-evolving model fluids by hybrid dual mixing systems
Gas dispersion experiments (0.18less than or equal toFrless than or equal to0.71,0.02less than or equal toFlless than or equal to0.09) were carried out using a hybrid dual mixing system, which included a helical ribbon impeller and either a Smith or a Rushton turbine. Newtonian and non-Newtonian model fluids were used as rheologically-evolving fluids to evaluate changes in gas dispersion performance. A motionless helical ribbon agitator was used as a baffle in low-viscosity Newtonian fluids. Both Smith and Rushton turbines produced a vortex, which was eliminated by the motionless helical ribbon impeller. Gas dispersion in low-viscosity fluids was enhanced when the helical ribbon agitator and turbine of the dual hybrid mixing system was kept at a rotational speed ratio of 10 (N-T/N-HR = 10), which allowed dispersion at a lower Fr than the turbine alone. For moderate-viscosity Newtonian fluids, gas dispersion was achieved at Frless than or equal to0.71 and Flless than or equal to0.05. Flow properties of non-Newtonian fluids played an important role in gas dispersion; transition from dispersing to flooding stages was observed for the fluids that were more shear-thinning (nless than or equal to0.38).