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:: Virtual Flotation Cells stir up Industry Interest
When it comes to separating valuable minerals from gangue, the minerals industry is perpetually striving for greater operational efficiency. But given the enormous difficulties of running physical experiments using industrial-scale flotation cells, one group of mineral processing companies charged a team of CSIRO fluid process engineers with developing a cost effective substitute.
Led by Dr Peter Koh, a team from CSIRO’s Minerals Down Under Flagship developed a virtual platform for experimenting with the flotation separation process, built using CSIRO’s extensive expertise with computational fluid dynamics (CFD). The project was sponsored by Rio Tinto, BHP Billiton, Outotec and Anglo Platinum through the AMIRA P780A program and resulted in the production of robust modelling systems for three types of flotation cells in commercial use - the Metso, Outotec and Wemco cells.
Dr Koh explains that while the geometry of these separation machines may vary, the physics of the separation process is basically the same. That means the same momentum, mass-transfer and turbulence equations are at play. To validate values for bubble drag, bubble break-up and coalescence in the model, the team ran physical experiments using pilot-scale cells.
For the Wemco configuration, these experiments involved building a transparent one-cubic-metre cell using Perspex and components supplied by commercial manufacturer FLSmidth.
Measurements were made using lasers and video analysis in CSIRO’s custom laboratory. The analysis was further validated using measurements made in industrial-scale cells at sponsors’ plants. “Essentially, the project involved building two tanks," Dr Koh says. “One is a see-through Perspex cell that sits in a blackened laser laboratory and the other sits inside a computer."
The software package aims to provide an accurate model to substitute as an experimental medium for improving cell design or to improve mixing and bubble-particle attachments at industrial operations. “CSIRO’s industry partners are very interested in the modelling technology," he says. “It has applications within their industrial operations that include solving problems with individual tanks, with scaling-up operations, and in finding ways to increase capacity and recoveries. “Models can explore the consequence of making changes such as increasing the feed rate or changing the particle size. These are situations where an operator can do the modelling first to identify optimum conditions before making changes or commissioning new flotation cells."
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