Monday, 4 April 2016

The rapidly changing face of comminution

With Comminution '16 only a week away I have been looking back on past conferences in the series, which began with Comminution '88 in Redruth, progressed to Australia, then Falmouth and since 2010 in Cape Town.
The last Australian conference, Comminution '06 in Perth was attended by only 48 delegates, but comminution then was in a bit of a rut, grinding being dominated by rod, ball and SAG mills, with little interest in stirred mills and High Pressure Grinding Rolls (HPGR). It was almost as if these were curiosities, rather than serious contenders to the well established tumbling mills.
From 2008 onwards delegate numbers rose rapidly to a maximum of 250 in 2012 when the industry was booming as a result of high commodity prices. But the real reason for the rise in comminution interest has been innovation in technology, and in the past decade, the minerals industry has finally woken up to the fact that comminution is expensive, particularly in terms of energy consumption.
HPGR and stirred mills are now increasingly used, the former crushing finer and the latter grinding coarser than in the past, so that we must ask whether tumbling mills will soon be things of historical interest. At Comminution '16 keynote speaker Tim Napier-Munn said in his summing up that "we really have to get rid of tumbling mills", and Joe Pease, in his keynote next week will ask whether the SAG mill could be regulated to a curiosity during the next few decades.
So there are interesting times ahead in comminution and I look forward with intense interest to next week and to reporting on events both on the blog and on Twitter (#Comminution16).
Twitter @barrywills


  1. I still feel, may be wrong also, that we focus only on particle and breakage. There are many other factors like size distribution of particles and the variations in the hardness of each particle size(because we are dealing with ores), the size distribution of media, the lifter design, the pulp density are not talked about much in the case of tumbling mills. How about the affect of cyclone performance on the mill (character of circulating load and its quantity)?Similarly let us list factors which are important(material and machine) while talking about sag mills/HPGR.


  2. Of course, we need to get rid of tumbling mills. The new stage belongs to crushers, HPGRs, Vertical Mill (tower mill) and Vertical Roller mills.
    A circuit with primary crusher, secondary and tertiary crusher followed by a vertical roller mill will consume about 7 to 10% less energy and NO steel balls.
    We could even get about 40% energy savings with this circuit that I just mentioned if we make a small change to use proven technology.
    All of these are proven technology. All we need is that someone has the courage (no, is not the grinding media) to do the testing to develop a circuit like this. Please quote me on this circuit when in 5 or 10 more years we see the first plant working with this idea. Please let me know if I can help your company save 40% in energy costs and all the grinding media in the crushing and grinding circuit or please let me know if you want me to discuss about it with you. My idea has already being rejected when presented to conservative people.

    So please make sure that you are open minded and a game changer before contacting me.

    Juan J. Anes, EM2PO, Vancouver, Canada

    1. Juan: Welcome to the industry where every company wants to be the fourth to adopt the latest technology.

      Kenneth Armstrong, Allnorth Consultants Ltd, Vancouver, Canada

  3. Looking at the list papers at Comminution '16 stirred mill technology is becoming even more popular. Exciting times ahead...
    Nick Wilshaw, Grinding Solutions Ltd, Cornwall, UK

  4. Eco-efficient comminution is the way to go. Unfortunately some industry clients and design engineers are still sceptical of using newer technologies such as Vertical Roller Mills, VertiMills, SMDs and HPGRs for new capital projects, citing CAPEX constraints and "unproven" technologies for a specific commodity/mineral. If we (the industry - engineers, clients & investors, designers, consultants, researchers etc) do not take the necessary steps towards sustainable and eco-efficient processes, comminution will remain our biggest (and ongoing) "headache" when it comes to energy use and sometimes lack of energy supply. It seems many of us in industry are prepared to integrate a single new technology into an existing operational plant (for expansion e.g.) after extensive testing and piloting, which is a good start, but major cost and energy benefits are relinquished in the initial stages of a new greenfields project where such newer technologies are not selected.

    Mxolisi Ntombela, Gekko Systems, South Africa

  5. I remember when for the first time I saw a SAG mill working in closed circuit with a cyclone and the cyclone overflow going to a Tower mill. There was no ball mill in that circuit. Then the rougher concentrate was regroud in an SMD.
    The SAG mill feed was 6-7 inches, the flotation feed was 40 microns, the regrind stage would take the p80 to 8-10 microns. That design took some courage but it worked perfectly. Then we did a first optimization and we took it to 68% (is not a typo) over design.
    Innovation can come in the shape of adapting technologies that are already proven. VRM´s have been in the cement industry since 1930 and engineers there are as respectable and as capable as the engineers working in copper. The VRM´s can grind slag too. The materials engineering on the liners of those mills evolved as the material engineering in base metals. What is the fear?
    We may not need an expert in grinding to put together these circuit but an exceptional seller of new technologies
    Juan J. Anes, Canada

  6. Unfortunately, many of the new 'crushing/grinding' machines do not have a length of history regarding wear and energy consumption in hard-rock applications.

    On top of that, senior managers that may be approving the purchase of new equipment for new projects are more comfortable with the 'traditional' comminution equipment that are 'proven' in similar applications, hence they will approve those traditional crushing/grinding equipment over something like HPGR, VRM, etc.
    It will take a couple of decades before they are accepted without question but the change will come about.

    Louis Bernard, Bernard Mining & Metallurgy, Canada

  7. Energy intensive sectors such as cement have already used HPGR in their circuits. Besides gold plants are using isamill in the comminution. I think 2016 will mature this opportunity for other mineral sectors to use new mill technologies such as stirring mills, tower mills, jet mills, attrition mills, vibrating mills etc.?
    Ugur Ulusoy, Cumhuriyet University, Turkey

  8. Louis, I agree with you only in that part of the approving managers. That is the main issue. I have investigated and immersed myself on these technologies and I would say that there both industries have no major differences in the type of materials used to improve wear. When a machine deals with slag you need to get creative with liners wear and these guys have managed to give you liners duration of over 9 months or a year. Ulgur is giving opinions in the same direction I mention here. Thanks
    Juan J. Anes

  9. It would be more valuable if we start giving examples of ores in consideration, what kind of tests done, what factors have been considered and then which particular type of comminution machine/circuit selected. The percentage of capital and power costs saved would also be of value.
    This will help the knowledge and decision makers.


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