Fluid flow in thickener feedwell models

Abstract

The design of feedwells in thickeners has a significant influence on the subsequent settling and classification performance. The fluid flow inside tangential entry feedwell models has been investigated in a small-scale physical model of the feedwell and simplified thickener. Laser Doppler velocimetry measurements have been made in feedwells with and without an internal shelf, and dye tracer has been used for flow visualisation. In a tangential entry feedwell without a shelf, the feed spiralled down the inner wall of the feedwell before exiting. With an internal shelf in the feedwell, the feed spiralled above the shelf before slipping over the edge of the shelf and spiralling down the inner wall of the feedwell. The increased spiralling resulted in an increase in the fluid residence time in the feedwell with an internal shelf. A single-phase, three-dimensional computational fluid dynamics model was used to calculate the fluid flow in the model feed-wells. The performance of the κ-epsilon turbulence model and the differential Reynolds stress turbulence model were evaluated. The numerical predictions of the velocity fields using both turbulence models were in good agreement with the experimental results measured inside the feedwell. The economical k-epsilon turbulence model may be used to assist in the design of feedwells for industrial thickeners. Crown Copyright © 2003 Published by Elsevier Science Ltd. All rights reserved.