CUED Publications database

Flow of wet powder in a conical centrifugal filter-an analytical model

Bizard, AFM and Symons, DD (2011) Flow of wet powder in a conical centrifugal filter-an analytical model. Chemical Engineering Science, 66. pp. 6014-6027. ISSN 0009-2509

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Abstract

A one-dimensional analytical model is developed for the steady state, axisymmetric, slender flow of saturated powder in a rotating perforated cone. Both the powder and the fluid spin with the cone with negligible slip in the hoop direction. They migrate up the wall of the cone along a generator under centrifugal force, which also forces the fluid out of the cone through the powder layer and the porous wall. The flow thus evolves from an over-saturated paste at inlet into a nearly dry powder at outlet. The powder is treated as a Mohr-Coulomb granular solid of constant void fraction and permeability. The shear traction at the wall is assumed to be velocity and pressure dependent. The fluid is treated as Newtonian viscous. The model provides the position of the colour line (the transition from over- to under-saturation) and the flow velocity and thickness profiles over the cone. Surface tension effects are assumed negligible compared to the centrifugal acceleration. Two alternative conditions are considered for the flow structure at inlet: fully settled powder at inlet, and progressive settling of an initially homogeneous slurry. The position of the colour line is found to be similar for these two cases over a wide range of operating conditions. Dominant dimensionless groups are identified which control the position of the colour line in a continuous conical centrifuge. Experimental observations of centrifuges used in the sugar industry provide preliminary validation of the model. © 2011 Elsevier Ltd.

Item Type: Article
Uncontrolled Keywords: Centrifugation Drying Filtration Laminar flow Porous media Powder technology
Subjects: UNSPECIFIED
Divisions: Div C > Engineering Design
Depositing User: Cron Job
Date Deposited: 07 Mar 2014 11:42
Last Modified: 08 Dec 2014 02:30
DOI: 10.1016/j.ces.2011.08.022