# Grinding & Classification Circuits

Grinding & Classification Circuits 2017-04-04T06:57:16+00:00
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## Ball Mill Charge (1 reply)

Carl Jenkins
2 years ago
Carl Jenkins 2 years ago

The crop load of ball mill. It =ore + mill medium +water. But usually, it was used in a percentage formation. So how to calculate this percentage. I know this is really a basic question, but it puzzled me, for most books and papers just use it but nor explain it.

Paul Morrow
2 years ago
Paul Morrow 2 years ago

The ball charge and ore charge volume is a variable, subject to what is the target for that operation. The type of mill also is a factor as if it is an overflow mill (subject to the diameter of the discharge port) is usually up to about 40-45%. If it is a grate discharge you will have more flexibility of the total charge. Ball size and ball grade is determined by the feed ore size and hardness, plus the PH level of the slurry. The ball charge is determined by the operator targeting the balance between grind and throughput, the higher the ball charge the more aggressive the milling becomes. With softer oxide ores lower ball charges are usual however the harder sulphides does need more media energies to meet the P80 target and an acceptable throughput. These comments are very broad and very much dependent on individual operator priorities. There are too many variables to cover every case in this forum. I will however mention that "spawling" has been now greatly reduced due to new media technologies and breakage of media in high ball charges is able to be overcome. High ball charges in ball mills does open that danger of media breakage through higher ball on ball incidents - now this is not the problem that it was previously.

Simply put, the levels of ore, media and water volume is determined by the targeted priorities of the operator and the type of mill that he has available.

See https://www.911metallurgist.com/blog/ball-mill-charge-volume-calculation

and https://www.911metallurgist.com/blog/estimate-charge-volume-of-a-grinding-mill-method-1 and https://www.911metallurgist.com/blog/estimate-mill-steel-charge-volume

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