Wednesday, 27 March 2013

Flotation research - does advancement require a paradigm shift?

Flotation has been a technology success story in providing metals and industrial minerals for mankind. Much of the technology development has taken place by industrial experience and trial and error. As the ore-base keeps changing, new challenges are arising. Lower grades require high volume throughput flotation technology for economy; more complex ores require the capability to handle finer feeds efficiently. Faster development will be needed as issues of material efficiency, use of water and tailings quality are becoming crucial for the acceptance of the industry.

After a century of research we are still struggling to fully understand flotation. There are several reasons for this, which will be discussed by Prof. Kari Heiskanen, of Aalto University, Finland, in his keynote lecture at Flotation ’13 in November.

The combination of two discrete phases in a turbulent continuum has proven to be full of challenges. Phenomenological models, embodied in the first order rate model and all derivatives thereof have, in Prof. Heiskanen’s view, come to the limits of their usefulness. We can and should use them to solve many practical issues where work can be based on laboratory experiments, but they will not give us any further understanding of the underlying physico-chemical phenomena involved. This understanding is needed, if we wish to develop new generations of effective flotation cells and processes.

Prof. Heiskanen will discuss the need to span research over several decades of scale, instead of working mostly on continuum scales. The momentum effects are multidimensional already in the continuum scale. The crucial point discussed will be the transfer of continuum momentum effects via the boundary layers to the molecular scale at these boundaries and the effects of boundary molecular structure to the continuum behaviour. This will be discussed in the light of a frother and bubble system. He will also refer to ideas of creating true multi-physics models for flotation. In doing so, some areas needing a deeper understanding will be identified and discussed.

What are your views on the future of flotation research?


  1. Great question & one that can be dissected from many perspectives:

    Regarding the machines:

    Stepping back from the present evolutionary process of cells, which is somewhat reminiscent of the trends observed with dinosaurs – some families getting larger and larger until…problems arise and other forms dominate. The present trend with cells and equipment seems forced, with a mindset of larger and larger flotation cells being the answer, however, it only fits certain circumstances.

    We need to revisit the question – separating valuables from waste in most efficient manner to produce in the end minerals which are converted to metals or industrial products.

    The opportunity exists for intensification of physical and chemical reactions following lines in chemical process industry. Threads of this can be seen in development work with alternative cells focusing on intensification of processes in the pulp and/or froth phase.

    Regarding the research:

    The large gap between research workers and incorporation of findings suggests:

    - the need to find improved paths for technology transfer
    - questions about the significance of the areas researched
    - questions about our understanding of the problem

    Robert Seitz, USA

    1. Robert-I agree with your thoughts.

      I am having trouble of the concepts of bigger tanks, with the usual selling point being LOM power cost savings.
      Sure can work some some styles of mineralisation, but is a long way from the fix-all. Now if we can only keep the accountants away from good engineering!

      The Russian cell develpers in the '70's worked away on many designs of intense pulp contactor then seperation in one unit. But this work did not develope further until maybe the very recent cells in current development.

      Then we had a fade of intensive conditioning, which seems to have been short lived.

      Generally I sense there is a much better understanding of the basic physio/chemical process both within grinding and immediately after with reagent additions.
      Hence Maggotteaux and ISAmill successes, combined the the upcoming trends of HPGR and stirred mills. Simply grind it properly and the resulting flotation chemistry is easier to control.

      I did attend Flotation '11, and was disappointed with the seeming 'academic' research being persued virtually independently, with little communication between highly intelligent researchers. Where do all these complex mathematical models add real value?
      Trevor Yeomans, Canada

  2. I'm not sure we need a paradigm shift. We must realise that if a sulphide flotation process produces a mineral concentrate at about 90% purity and 90% recovery, then there is not much left for improvement. I know that in most mineral systems there are alternative reagent schemes available from manufacturers of flotation chemicals, but they are not marketed since there is no market!
    For oxide minerals, the picture is somewhat different, but the development is fairly slow. You see for example the increasing use of sarcosinates for apatite flotation instead of modified carboxylic acids, and hydroxamates in REE flotation. But the use of such reagents must of course be justified on a cost-profit scale.
    Looking at the whole mineral processing landscape, we must realise that there are several methods that are cheaper or better than just flotation. Wet gravity methods are very efficient for high density metal minerals, and hydrometallurgy has over the last decades replaced copper oxide flotation. In my view, we must consider flotation as a good process for upgrading small amounts of valuable minerals into concentrates that can be fed to over upgrading schemes. Flotation is not a general solution.
    So back to the initial question; need for a paradigm shift? No but for continuous improvement in small steps (the Japanese has word for it - Kaizen).
    Bertil PĂ„lsson, Lulea University, Sweden

  3. What does advancement mean? I suspect this varies depending on the person being questioned.

    For some, it would be understanding of the process (Theory); while for others, industrial performance of the process (Practice).

    What would advancement mean to you?
    Robert Seitz, USA


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