Grinding & Classification Circuits

Grinding & Classification Circuits

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Inverter controlled iron ore ball mill grinding (3 replies)

T
Tony Johnston
6 years ago
Tony Johnston 6 years ago

Does anyone have a couple of examples where iron ore is being ground using a ball mill with an inverter for mill speed control?

And if you do, can you offer any commentary on how successful, in technical and economic terms, that approach is proving to be?

I ask on behalf of a Japanese company that wants to build a better business case for a proposal they are want to make.

Many thanks.

David
6 years ago
David 6 years ago

Hi Tony,

Someone published a paper on it, the advantage is that it gives you a soft start capability. In case of a short term process interruption then you could avoid “frozen charge” by keeping the mill going at low speed. If the ore hardness varies a lot and tonnage is maximized then slow down to avoid over grinding and save energy. 

Maybe you found the paper. Post them here if so.

Here is one also https://library.e.abb.com/public/d43c675f94ad66abc125793d0056168e/COPPER%20MOUNTAIN%20-%20OVERVIEW%20ON%20THE%20GRINDING%20MILLS%20AND%20THEIR%20DUAL%20PINION%20MILL%20DRIVES.pdf

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T
Tony Johnston
6 years ago
Tony Johnston 6 years ago
1 like by David

David,

Thank you for your response and the link to the great paper you found on the use of a ball mill with an inverter for mill speed control in a cooper ore processing situation.

Taking the suggestion offered by your comments, I was able to source the attached PDF from one of the authors on STEPPING FORWARD: USING VARIABLE SPEED DRIVES FOR OPTIMIZING THE GRINDING PROCESS IN SAG AND BALL MILLS by I. Atutxa and I. Legarra, which was presented at the 2015 SAG Conference in Vancouver.

The only further thing that ideally I would like to get is one to three examples of the use of variable speed drive ball mill grinding of iron ores. Does anyone know if and where such are in operation?

Many Thanks / Cheers,

Tony

David
6 years ago
David 6 years ago

My friend from https://sagmilling.com/ says most iron ore mines don't use ball mills for a couple of reasons:

1. The grind is coarse enough that you can do it in a single stage (Eg. Labrador Trench) or no grinding is required at all (Pilbara and Brazil direct-shipping iron ores).

2. More cost-effective to use pebble mills instead of ball mills (Eg. Swedish iron mines).

The only variable-speed "ball mills" I can think of would be the ones at Sino Iron, and they are variable-speed because the mills are so big that the only drive technology they can use is gearless, and gearless drives are inherently variable speed. If a fixed-speed alternative had been available, then it is not obvious they would have chosen variable speed.

One uses variable-speed ball mills when the overgrinding caused by soft ore is bad for the downstream process (making slimes). If your process isn't sensitive to overgrinding, then don't both with variable speed.

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