Crushing, Screening & Conveying

Crushing, Screening & Conveying2017-04-04T06:57:13-04:00
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Popularity of Stirred Mills and HPGR (2 replies and 2 comments)

1 month ago
Dachmann 1 month ago


I am new to the field of mining. Recently I looked into the process of liberation and concentration. Many papers suggest that HPGR and Stirred Mills are a better alternative to SAG and Ball mills in terms of energy efficiency and mineral liberation. Many papers say that the higher CAPEX is compensated by the lower OPEX.

Why then, do not all mines or at least the majority that are under construction rely on these grinding technologies? What is the reason for the ongoing popularity of conventional tube mills?

I also realized that all types of mills are multi MW by now, expect from stirred mills. Those still have a rated power of a few MW. Is there any explanation to that?

Thank you for your answers!



Alex Doll
1 month ago
Alex Doll 1 month ago
1 like by Dachmann

Hi Dachmann, welcome to the Forum.

Don't get distracted by energy efficiency, it is economic efficiency that matters in Capitalist economies.  The process path that is most economically efficient will change depending on ore characteristics, location, climate, and economic factors like NPV discount rates and sovereign risks.

I wrote an article with a specific case study for a Western Canadian climate that you may have seen online:

Regarding stirred mills, the two issues you haven't touched on are they can be a pain in the butt to do maintenance on (you have to dump the mill contents of the floor which you don't do with a tumbling mill) and sometimes they have issues with the top size of material that comes from upstream stages (you need to match the media size in a stirred mill its feed top size).  And you need lots of units to match the capacity of one large gearless tumbling ball mill, so that are capital cost inefficient.  When we see multi-Megawatt stirred mills that have an elegant maintenance program, then I expect we'll start to see more of them in secondary grinding duties.

4 weeks ago

Thank you very much for your detailed answers and the links you provided.

1 month ago
SmartDog 1 month ago
1 like by Dachmann

Similar to Alex's comments on the stirred mill, HPGR also have maintenance and capacity issues.  You need several to equal one SAG or ball mill.  This requires a lot of chutes and diverters that are major wear points.  You also have to have more conveyors to collect the product.  All this adds up.

4 weeks ago

Thank you for your answer. The additional maintenance requirements are often ignored in studies. Good point.

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