Grinding & Classification Circuits

Grinding & Classification Circuits

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Bond index for "fine" ore and different sieve size (1 reply and 1 comment)

P
rakavka
7 months ago
rakavka 7 months ago

Hi guys,

I have to calculate a new throughput of the existing grinding circuit with a new finer ore. 

I'm trying to calculate a BM working index of the new ore with 300 um sieve size.

The problem is that amount of undersize in feed is higher then 250% circulating load (CR) so I get negative mill revolution.

I've though of some solutions:

  1. To decrease the sieve size and get probably a higher work index.
  2. Decrease a CR to say 150%.
  3. Remove part of -300um from testing ore in first run (?)

What should I do? Is there a better solution?

Also, if I change a sieve size tested from 150 to 300um, is there anything I need to change in specific energy consumption eq.? 

Thanks in advance

PM

Alex Doll
6 months ago
Alex Doll 6 months ago
Like
1 like by rakavka

Hi Rakavka

Yes, you should screen the 300 µm out of the feed to the first cycle to get the test started, but the make-up feed to the remaining cycles should not be pre-screened.

You should run two tests, one with the 300 µm closing screen and the second with the 150 µm closing screen.  I expect the 300 µm result will be significantly higher Wi than the 150 µm result.

It is a good idea to make sure that your feed is properly prepared since I do not run into this problem very often.  The feed should have been stage-crushed down to 100% passing 3.36 mm and it should approximate a Gaudin-Schuhmann particle size distribution (use https://granulometrics.com/ to check the PSD regression models).  If the PSD deviates significantly from the G-S model, you might have a feed that isn't suitable for performing the test.

-AD

https://www.sagmilling.com/

P
rakavka
5 months ago

Hi Alex,
I eventually used Magdalinovic rapid method which by-passes the fines problem. Isn't it opposite? the smaller the sieve, the higher Wi? For a finer product we need to put more energy..?
Thanks in advance
Rakavka

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