Study of critical suspension speed of impeller in two paddles stirred kettle

Abstract Experiments and numerical simulations were used to study the two-layer paddle stirring system. Glass bead particles and aqueous polyvinyl alcohol solution were used as the solid-liquid phases, and the variation of the critical suspension speed of impeller Njs under different parameters was analyzed by testing the parameters of liquid phase viscosity, solid phase particle size, and solid-phase mass fraction. The results showed that the main resistance (surface viscous resistance) increased with the increase of liquid-phase viscosity at particle size d=0.3 and d=0.5 mm, and this factor inhibited the solid-phase diffusion, resulting in an increasing trend of Njs with the increase of liquid-phase viscosity. At particle size d=0.8 and d=1mm, the main resistance (gravity) is not related to the liquid phase viscosity, and the intensity of turbulent pulsation in the kettle is enhanced with the increase of liquid phase viscosity, which is favorable to the solid phase diffusion, and Njs decreases with the increase of liquid phase viscosity. The increase in solid-phase volume fraction increases Njs.