Power Consumption Diagram for Wet Particle Kneader Mixers —In the Case that Rheological Properties for Wet Particles cannot be Measured—

Abstract

A method to draw power consumption diagrams (N_p-Re diagram) for kneader mixers dealing with wet particles which have a high particle content and a flow curve showing plastic fluid characteristics are proposed. The method requires only power consumption measurement of kneader mixers. Rheological properties measured with a rheometer are unnecessary.
The proposed method was developed based on Nagata’s method, which was designed to draw N_p-Re diagrams using the Metzner-Otto concept for mixing vessels containing a low-particle content.
For drawing N_p-Re diagrams, we used Casson equations and the Metzner-Otto method to represent the relationship between apparent viscosities and shear rate. The procedure of the present method is as follows. Firstly N_p-Re diagrams for Newtonian fluids are made. Secondly, mixing power consumption is measured for wet particles by varying rotational speeds. Then ratios of yield stresses to the specific equipment factor of the kneader mixer, τ_c/B, and Casson viscosity, μ_c, are estimated. Finally N_p-Re diagrams can be obtained using corrected Bingham numbers and impeller Reynolds numbers based on Casson viscosities. Then, we ascertained that an N_p-Re diagram is determined solely by Reynolds numbers based on apparent viscosities, and the N_p-Re diagrams drawn by the method in this study are independent of the kind of wet particles and the scale-up ratio of the kneader mixer.