Grinding & Classification Circuits

Grinding & Classification Circuits

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Ball Mill Cyclone overflow P80. (2 replies and 3 comments)

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Nickbob
8 years ago
Nickbob 8 years ago

I would like to know the effect of ball mill cyclone overflow density on P80 of 150um. I ask this because at either higher or lower densities, you can get your P80 @ 150um (at least 80% passing 150um). Kindly advise on what densities would you get the P80 best for floating chalcopyrite to get optimum recovery (close to 99%) and con grade (above 30%Cu)? We are using aero 3894A or MX965 as collectors and Polyfroth (W22) as frother.

David
8 years ago
David 8 years ago
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Nick, how do you control that cyclone density?  Water to cyclone feed box OR add to cyclone overflow?

Are you saying that changing from 25% to 35% solids does not affect your P80?

Unless you have a high clay content in your ore, you should run thicker 35%++ to maximize flotation retention time.

You can run some test densities at https://www.911metallurgist.com/blog/calculate-flotation-cell-capacities-volume-vs-retention-time

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N
Nickbob
8 years ago

We control the density by adding water to the feed box or usually pump pressure adjustment. Cyclone overflows gravitates straight on to the flotation roughers.
Yes I am saying that at higher densities like 37slurry pulp density Vs 7 (+150um sieve density), you get P80 of 85%. And also at 23 slurry density Vs 4 (+150um sieve density), you get P80 of 80%.

David
8 years ago

Are there any reasons you run such a low density?

David
8 years ago
David 8 years ago
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OK. What is making you run with low densities?

PS: this tells me your grinding circuit/plant could produce much more tonnage.

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Craig Lockhart
8 years ago

Gents,
Sounds to me like the cyclones are not optimized - what size/brand cyclones are you operating? How many? Inlet pressure target? Orifice sizes?
Sounds like you could get a lot more efficient on your classification for benefits on the grind size and the throughput while maintaining overflow density in the mid-30s.
If your apex is too large, your circulating load will be higher - this can reduce capacity for new feed and increase tendency to over-grind. If your vortex finder is too large, coarse oversize will report to overflow, affecting recovery. If your inlet is too large, inlet velocity will be too low and the overall split will not be sharp. In the past, rule-of-thumb dictated 7-9 psi for secondary grinding cyclones and 14-18 psi for regrind, mainly to balance performance and wear rates...with improvements in classifier design and wear materials, you can typically operate secondaries at up to 18 psi and tertiary/regrind at over 20 psi.
Your best-floating particles should be in the 25 - 80 micron range. Adding cyclone water to the mill feed may be a good option in your case to reduce over-grinding/sliming without going overboard on reducing flotation feed density.
Good luck with your efforts Nickbob!

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