Grinding & Classification Circuits

Grinding & Classification Circuits 2017-03-23T09:46:37+00:00
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Energy Intensity Calculation of Grinding Circuits (1 reply)

Paul Morrow
1 year ago
Paul Morrow 1 year ago

Based on the data I collected from the client, we have the total power, P80, and F80 for the grinding circuit but not the values for the various circuit components (crusher, ball mill, rod mill and tertiary mill).

Would it be correct to apply the bond equation (link below) using the values for the total circuit without doing the calculation for the separate components first?

I also have the SMC test for the circuit. Can I use that to calculate the overall energy intensity of the grinding circuit or does is it only for individual components as well?

1 year ago
David 1 year ago


I conferred with my friend at and he says the short answer is yes. The SMC test is one way that you can "benchmark" an operating mill against a theoretical power consumption for a "typical" grinding circuit. There is another method using Bond-type testing that I normally prefer, but I do use SMC in my work.

If you look at the Appendix of your SMC test report, you will see a calculation example for determining the energy to grind from a feed size (F80) to a product size (P80). The equation is in two parts, and you need a Bond ball mill work index determination to complete the second part. With the SMC and ball mill work index tests, Morrell claims you can determine the total specific energy from the primary crusher to the hydrocyclone overflow, and with minor changes described in his example you can use it for any type of grinding circuit.

That equation describes the total circuit energy. To determine the energy for the individual components of the circuit is more difficult, and I use a method that Morrell dislikes to distribute energy between stages using a transfer size. I describe the technique in the short courses that I teach, but it is not something I can describe in an email. I also see software that does these sorts of calculations using Bond or SMC/Mi equations ($3k to $5k per year subscription rates).

If your circuit is a rod mill and ball mill circuit, you will be much better off using a Bond analysis rather than SMC. The only thing to be careful of is that the laboratory uses a Bond rod mill with a wave-type liner. There are laboratories who claim to have a "rod mill work index" apparatus, but they use a smooth liner which is wrong and Bond's equations are not calibrated to that liner geometry. 

If you let me know where you live, I can recommend laboratories that you can use who have the correct geometry.

Hope this helps.

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