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Flotation ‘03, part of the Minerals Engineering International Conference Series, was held in Helsinki, Finland. The conference was held in association with the Helsinki University of Technology, and Australia’s Ian Wark Research Institute. Sponsors of the conference were Outokumpu Technology, Metso Minerals, David Wiseman Pty Ltd, and the Minerals Gazette. The conference attracted over 110 delegates, representing 18 different countries.
The presentations were comprised of 16 posters and 42 oral deliveries. Full papers from the presentations will be peer reviewed on submission and those accepted will be published in a special Flotation issue of Minerals Engineering journal later in the year. The technical sessions covered most aspects of mineral flotation including: (1) Fundamentals, (2) Flotation Froths, (3) Control, Simulation and Optimisation, (4) Flotation of Specific Minerals, (5) Plant Operations and Machines, and (6) Reagents. There was a good blend of research and vendor related papers, covering a wide variety of issues in mineral flotation. A greater contribution of speakers from industry would have added value to the conference as a whole.
The Fundamental session focussed on (1) Effect of particle hydrophobicity on bubble size in a flotation cell, (2) Removal of iron hydroxide coating from galena surface, (3) Measurements of gas dispersion in flotation cells, (3) Recovery of nanoparticles by flotation, (4) Bubble-particle interactions in flotation. An interesting paper on nanoparticle flotation revealed an increase in flotation rate of particles less than 3 microns, as noted by other researchers. This was ascribed to a diffusion mechanism which would operate independently of the particle’s hydrophobicity. The key role of particle hydrophobicity on micro-bubble formation at the particle surface and particle-bubble attachment was not explored in the discussion. Another important point is that significant changes in bubble size with different particle hydrophobicities will make process modelling, of the type which ignores variations in feed properties, more difficult to apply in practice.
The Flotation Froths session focussed on (1) Understanding and measuring factors influencing froth stability in flotation, (2) Image analysis and computer vision for mineral froth, (3) Distribution of wash water in a flotation froth, (4) Influence of gas flow rate and surfactants on liquid drainage in flotation froth and foam, (5) Recovery of water from a flowing foam column, (6) Dynamic froth stability in froth flotation. A paper demonstrated the very significant advances in machine vision technology which has occurred in the last few years. Here, dynamic froth images were presented in which coalescing and bursting bubbles were detected and quantified. Separately, a key issue in froth phase modelling is the prediction of water recovery across the froth. It is clear that fundamental measurements of interfacial (gas/liquid) rheology, both in the presence and absence of particles, are required for these models to be validated and applied.
The Control, Simulation and Optimisation focussed on (1) Future trends in flotation plant control and automation, (2) Application of the P9 flotation modelling methodology to flotation circuit diagnosis, design and optimisation, (3) Froth recovery measurement in plant scale flotation cell, (4) Process optimisation with Outokumpu's plant audit procedure, (5) Model and imaging of froth for control of flotation, (6) Utilising PLS and PCA in the interpretation of multi-camera data, (7) Modelling mineral recovery in flotation by combining process and particle image analysis data, (8) Towards the development of froth based control strategies in flotation circuits based on vision systems: an industrial case study, (9) CFD modelling of collisions and attachments in a flotation cell, (10) A proven flotation plant design and analysis methodology, updated for use in spreadsheets, (11) Controllability analysis of flotation. An excellent practical paper was presented which predicted the flotation rate of composite particles as the average of mineral flotation rates weighed by effective mineral areas determined by image analysis.
The Flotation of Specific Minerals session focussed on (1) Potential use of flotation techniques to remove transition metal sulfides from contaminated dredged material and soils: an overview, (2) Effect of copper and calcium ions on the flotation behaviour of a pentlandite-pyroxene system at pH 6 and 9, (3) Separation of plastic waste by froth flotation, (4) Development of a method for separation of PVC and PET using flame treatment and flotation. This session was dominated by the application of the flotation technique to environmental issues. An interesting paper demonstrated that different plastics could be separated in flotation by controlling the interfacial tension of the separating medium (gas/liquid).
The Plant Operations and Machines session focussed on (1) Garpenberg- an old concentrator at peak performance, (2) Jameson Cell fundamentals: a revised perspective, (3) The interaction of flash flotation and closed circuit grinding, (4) Recovery of lost platinum from tailings by high intensity flotation, (5) Grinding for success, (6) The effect of grinding conditions on the flotation of a sulphide copper ore, (7) The role of mineralogical studies in optimising mineral processing at North American Palladium's Lac des Iles mill, (8) New concepts in flotation machine design, (9) Effect of impeller speed and the froth phase on the size dependent flotation rate of galena in a full scale plant cell. Two papers demonstrated the importance of grinding media composition on sulphide mineral flotation recovery and selectivity. Separately, two papers discussed the effect of power applied to the flotation cell on improving bubble-particle collision rates and improving the overall rate and recovery of fine hydrophobic particles.
The Reagents session focussed on (1) Headspace analysis gas-phase infrared spectroscopy: a new tool for investigating flotation collectors, (2) Development of methodology to elucidate the relationship between the characteristics of polymeric depressants and their effect on flotation performance, (3) Ammonium sulphate as promoting agent of the sulphidization process of Cu-Co oxides ores from the Luiswishi deposit, (4) Adsorption of starch, amylose, amylopectin and glucose monomer and their effect on the flotation of hematite and quartz, (5) Direct observation of a self-assembled monolayer of heptylxanthate at the germanium/water interface, a polarized FTIR study, (6) Feasibility of microorganisms as flotation collectors and depressants, (7) Use of biosurfactants in flotation: application to metal ions removal.
The conference was of sufficient magnitude and breadth to be able to make some general comments on the direction of flotation research and practice. Of specific interest was the continuing emphasis on new techniques such as ToF*SIMS for the surface analysis of individual mineral phases in mixed system, and a strong research thrust on water transport mechanisms in flotation froths. Image analysis of flotation froths is rapidly becoming a routine technique for flotation plant control. However, a key feature of flotation froths, which still needs research, is how the frother surfactants and particles together influence froth water drainage and froth stability. Modelling and improving the capture efficiency of fine and ultrafine particles is a continuing research theme, while research on coarse, composite, particle flotation behaviour is still in its formative stages.
In general the papers were of a high standard, though some papers suffered from a lack of peer review prior to the conference. In conclusion, the conference was well attended, well organised and held in an excellent venue.
Stephen Grano, Ian Wark Research Institute, University of South Australia, Adelaide. Australia. Email: Stephen.Grano@unisa.edu.au
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