Crushing, Screening & Conveying

Crushing, Screening & Conveying2017-04-04T06:57:13-04:00
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SAG mill VS Ball & Rod Mill (2 replies and 1 comment)

Nikita Gupta
2 months ago
Nikita Gupta 2 months ago

I would like to understand why do companies use SAG mills instead of Rod mills for grinding these days? Apart from the alleviation of need for secondary and tertiary crushers, is there any other reason for inclination towards the installation of SAG mills. 

2 months ago
SmartDog 2 months ago

The main reason is capacity versus plant area.  Rod mills have a major restriction in length to diameter, they have to be significantly longer than their diameter to prevent the rods from tumbling and turning into a twisted knot.  SAG mills are the opposite, they generally have a larger diameter than their length.  This gives them an inherent higher capacity for a given length.  Rods are also generally more expensive than balls and harder to handle.  This means a rod mill equal in capacity to a ball or SAG mill would take up more plant floor area requiring a larger building.

Also since SAG (semi-autogenous grinding) uses less media than a comparable rod or even ball mill.  While less efficient in actual grinding SAG mills are lower capital and operating cost per unit ground, especially at large particle sizes.

Nikita Gupta
2 months ago

I actually did a cost benefit analysis and found that for use, the per unit cost was lower in the stream that used Rod Mills as compared to SAG mill. Is this an anamoly?

Alex Doll
2 months ago
Alex Doll 2 months ago

In addition to issues described in the earlier comment, you can make SAG mills bigger than rod mills.  The largest SAG mills consume around 25,000 kW whilst the largest rod mills consume less then 2,500 kW.  It is better to install one large SAG mill than 10 small rod mills.

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