New Challenges for Gravity Concentration and Classification of Fine Particles

“The net zero emission” mantra may prove to become the new “mother of invention” for minerals processing, says Prof. Kevin Galvin, Director of the ARC Centre of Excellence for Enabling Eco-Efficient Beneficiation of Minerals at the University of Newcastle, Australia, where he is Laureate Professor. 

Prof. Galvin is the inventor of the Reflux Classifier used in gravity separation of fine particles. With over 180 installations around the world, the technology has been used to beneficiate coal, iron ore, mineral sands, potash, chromite, and other base metal oxides. New innovative systems are emerging including the Graviton and the Reflux Flotation Cell through collaboration with FLSmidth. He has also been developing a novel agglomeration technology with Jord International.  He is a Fellow of the Australian Academy of Science and Australian Academy of Technology and Engineering and previous recipient of numerous awards including the Antoine Gaudin Award in mineral processing, so we are honoured that he has accepted an invitation to present a keynote lecture at Physical Separation '22 in May.

Kevin Galvin (right) at Flotation '13

The need for change is locked in, and rising, providing the ideal platform for creating new opportunities, especially in gravity concentration and classification. The challenge is to identify and deliver what is required and Kevin's keynote lecture will be concerned with the gravity concentration and classification of particles in water, involving particles typically finer than 1.0 mm. One of the greatest challenges is in delivering large scale, highly efficient, desliming at ~10 microns to overcome the effects of viscosity, and in turn maximize the value of the resource. This need is most apparent in one of the world’s most significant commodities, iron ore.  

There should also be a much greater role for gravity concentration across this full‐size range, increasingly in the range below 0.1 mm, the historical preserve of flotation. If the particle density can deliver sufficient selectivity, then in principle gravity concentration should be considered. This is especially true in reverse flotation which requires a multi‐stage flowsheet, very large foot‐print, and chemicals to deliver what could be achieved in a single physical stage of gravity concentration.

Mechanisms for amplifying segregation forces, including G forces and inclined settling, need to be exploited to deliver the necessary solids throughput.  Classification will be challenged by the emerging requirements for both gravity concentration, comminution, and coarse/fine particle flotation circuits in straddling the size range from 1.0 to 0.1mm through 0.1 to 0.01 mm. 

While in principle mechanical screens offer the ideal classification, the hydrodynamic approach may ultimately deliver the robustness, control, throughput, and efficiency despite the variation in separation size with particle density, provided synergy can be realised by integrating correctly within the overall circuit.

Prof. Galvin's keynote will be one of two keynotes at the conference; Prof. Neil Rowson will discuss the role of magnetic separation in the development of critical and strategic metal recovery flowsheets (posting of 25 October 2021).

There is currently a final call for abstracts for Physical Separation '22, which should be submitted by the end of this month.

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