Flotation in a novel oscillatory baffled column

This thesis presents an evaluation of an Oscillatory Baffled Column as a novel flotation device and as a research tool for investigating the role which hydrodynamics play in promoting particle-bubble contacting. The cell differs from a conventional cell design in that bubble generation is decoupled from the power input. This allows the hydrodynamic environment to be optimised for effective particlebubble contacting. The design also incorporates a novel mechanism of agitation which provides a more even distribution of shear rate than would be obtained in a stirred system and allows considerably more variation of the power input to the cell. Based on these properties it is hypothesised that the OBC would provide an effective hydrodynamic environment for fine particle flotation, particularly in highly viscous, non-Newtonian slurries. It is also hypothesised that the development of such a cell technology will facilitate an improved understanding of the role which hydrodynamics play in promoting particle-bubble contacting. To investigate these hypotheses, the OBC was first characterised in terms of key flotation parameters, such as bubble size, gas hold-up and mixing. The cell was then flotation tested on quartz, in order to benchmark the study against previous studies on hydrodynamics and particle-bubble contacting in stirred systems. Finally, the OBC was tested in application to a highly viscous, non-Newtonian nickel ore slimes slurry which is difficult to treat using conventional cell technologies. This study gave context to the potential future role of OBC technology in the minerals processing industry. The results of this thesis clearly show that the OBC is a promising novel technology for the treatment of fine mineral slurries. The cell has been demonstrated to significantly improve flotation kinetics by a factor of between 1.4 and 1.6 relative to a standard column. Optimal flotation conditions were obtained at power dissipations as low as 10 W/m3. The advantages of the OBC as a novel device include its ability to decouple bubble generation and particle-bubble contacting, its even distribution of shear rate in the cell as well as the additional fluctuating fluid motion produced under oscillatory flow. Furthermore, the flotation kinetics in the cell were shown to be unaffected by slurry rheology indicating the cell is best suited to niche application in the processing of ore types exhibiting highly viscous non-Newtonian behaviour.

Grantor dc:publisher.institution

Department of Chemical Engineering

Year dc:date.issued

2008

Author dc:creator

• Anderson, Christopher James

Advisors dc:contributor.advisor

• Deglon, David
• Harris, Martin

Language dc:language.iso

eng

Handle dc:identifier.uri

http://hdl.handle.net/11427/5340

OAI identifier oai:identifier

oai:open.uct.ac.za:11427/5340