Thursday, 1 June 2017

Towards large scale microwave treatment of ores

Microwave treatment of metalliferous ores has long been investigated as a means to enhance the recovery of valuable minerals and reduce the comminution resistance of ores, but despite over thirty years of work, microwave pre-treatment processes for beneficiation of ores have not progressed much further than laboratory testing.
Selective heating of microwave-absorbent sulphides and metal oxides deported in a microwave-transparent gangue matrix results in differential thermal expansion of the heated phase, yielding micro-fracture around grain margins. Subsequent downstream processing may then yield higher recovery of valuable mineral sulphides and/or lower specific comminution energy, compared to non-microwave treated ore.
Whilst the mechanistic principles are well established, the scientific and engineering challenges of developing a commercial scale system are immense. Typical throughputs of a large copper mine can be in excess of 5000 tph of milled ore and a microwave based treatment system would need to handle equivalent throughputs. This is at least an order of magnitude higher than any other microwave process ever built.
Which is why a paper in Volume 109 (2017) of Minerals Engineering is of immense interest. Workers from the University of Nottingham, UK, and Jenike & Johanson, USA, have detailed the design, commissioning and operation of a system which was the culmination of over fifteen years of research and development activity. This resulted in a pilot-scale high power microwave treatment process, capable of operating continuously at throughputs of up to 150 tph, but crucially scaleable up to several thousand tonnes per hour.
This paper is Part 1, which describes the basis of design, construction and commissioning. Part 2, which was accepted for publication in Minerals Engineering just over a week ago, and will soon be on ScienceDirect (I will alert in a comment), describes metallurgical testing, showing that comminution and liberation benefits are achievable at doses lower than that previously reported in the literature, which allow high throughputs to be sustained with low installed power requirements, providing a pathway to further scale-up of microwave treatment of ores.

3 comments:

  1. I had personal experience on the application of microwave on a sulphide ore; I must confess that it was not a great success and did not give confidence that this application would be economically and process wise feasible in a large scale operation.
    I am not making a judgement--perhaps more technical developments took place.
    I am eagerly looking forward to reading the details.
    Yes, I agree that attempts must be made to reduce power costs in comminution. My point is mainly that a bit more understanding of the ore characteristics and affect of microwave on the breakage has to be studied and understood before one thinks of application for large scale operations.
    Rao,T.C.

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    Replies
    1. TC, there have been many papers published over the last few decades on the fundamentals of microwave treatment of ores, many of these in Minerals Engineering. The earliest work involved little more than kitchen microwave units, and was essentially blue sky research as there was no apparent practical use on a large scale. But a great deal of knowledge as to how minerals behave under microwave heating was built up, much of it from the Nottingham University workers, so it is great to see that all this fundamental research might now be leading to full scale industrial operation.

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  2. Thanks, Barry, for giving more information.
    Let us encourage "out of box thinking" and I am looking forward to see industrial applications and the experiences.
    All the best.
    Rao,T.C.

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