Grinding & Classification Circuits

Grinding & Classification Circuits 2017-04-04T06:57:16+00:00
  • To participate in the 911Metallurgist Forums, be sure to JOINLOGIN
  • Use Add New Topic to ask a New Question/Discussion about Grinding.
  • OR Select a Topic that Interests you.
  • Use Add Reply = to Reply/Participate in a Topic/Discussion (most frequent).
    Using Add Reply allows you to Attach Images or PDF files and provide a more complete input.
  • Use Add Comment = to comment on someone else’s Reply in an already active Topic/Discussion.

Optimum Grind Size (10 replies and 8 comments)

Nickbob
1 year ago
Nickbob 1 year ago

In a chalcopyrite concentrator, what is the best flotation feed, grind size that you can do in order to optimise flotation operations? Maybe as in size distribution?

David
1 year ago
David 1 year ago

Hi,

what is the nature of the chalcopyrite?  A porphyry copper? What are your current results?  Ore head grade, concentrate grade, recovery and current grind size & plant tonnage?

Use the Social Share Bar on the Left. Tell everyone you can about https://www.911metallurgist.com/metallurgy/ It's FREE & GOOD.

Nickbob
1 year ago

Hello david,
Thanks for a quick response and sorry for delayed reply. However, the chalcopryte is a porphyry copper. And we are doing a through put of average 200t/h, feed grade average of 2%Cu at a recovery of about 85-90%. Concentarte grade of about 25-27%Cu.

David
1 year ago
David 1 year ago

What is you current grind size Nick?

At 2% Cu feed, (unless you have oxide?) your recovery should be near 99% .

Did you look at https://www.911metallurgist.com/blog/effect-of-primary-grind-size-on-mineral-liberation

Typically, you need to be finer than 200um but no need to be under 150um.

If you are near or under 200um; you have another problem...

Do you have more data?  Lab tests?

Use the Social Share Bar on the Left. Tell everyone you can about https://www.911metallurgist.com/metallurgy/ It's FREE & GOOD.

Nickbob
1 year ago

Hello David,
Thanks for your response. Our ore is chalcopyrite with very minor traces of oxide copper.We are grinding between 150um and 200um.Our flotation feed grind size is P80 @ 150um (design criteria) at densities between 25 and 35.
Reagents we are using are Aero 3894 and/or MX965 as collectors and W22 as frother.
We are not using any depressant as the pyrite in the ore is not very significant amounts.
We rarely get 95% recovery. Our con grade ranges between 24%-27%.
I will be very glad to hear from you on this matter.

David
1 year ago
David 1 year ago

Nick, 

Am sure your P80 is good. Are you able to post a Flowsheet here?

What is MX965?

W21 is pretty weak Nick.  W31 is the minimum here for porphyry copper. W31 being a Dow 250C replacement.

W21 will leave coarse copper behind as its bubble will burst to early.

Aero 3894 is also weak...

Use the Social Share Bar on the Left. Tell everyone you can about https://www.911metallurgist.com/metallurgy/ It's FREE & GOOD.

Nickbob
1 year ago

Hi David,
Aero-MX 965 is a sulphide mineral collector from Cytec. Frother is W22 (Polyfroth) and not W21. Aero- 3894 is also weak. Whats the best collector on the matter with the information at hand? I am trying to see if I can get you the flowsheet here. Thanks very much.

David
1 year ago
David 1 year ago

My mistake, yes W22, still weak.

Porphyry copper collector = PAX or SIPX = simple and cheap.

AERO 3894 promoter - due to its high selectivity, it generally requires the conjoint use of a xanthate to insure maximum recovery of middling (composite) particles. Being water-insoluble, addition to the grinding circuit is often beneficial.

PAX could likely replace both Aero-MX 965 and Aero- 3894.

I will wait for your flowsheet.

Use the Social Share Bar on the Left. Tell everyone you can about https://www.911metallurgist.com/metallurgy/ It's FREE & GOOD.

David
1 year ago
David 1 year ago

Use the Social Share Bar on the Left. Tell everyone you can about https://www.911metallurgist.com/metallurgy/ It's FREE & GOOD.

Nickbob
1 year ago
Nickbob 1 year ago

Hello David,

I have attached the flowsheet for your perusal for your advice.

David
1 year ago
David 1 year ago

Thanks Nick.  What are a typical 1st cleaner tails assay?  %Cu and %Fe%

+ What is the %Fe in the plant feed?

Use the Social Share Bar on the Left. Tell everyone you can about https://www.911metallurgist.com/metallurgy/ It's FREE & GOOD.

Nickbob
1 year ago

Hi Dave! Ist cleaners tails gravitate to the cleaner scavenger while the cons are pumped to the recleaners which are the 2nd cleaners as you can see on the flow sheet.
Otherwise the cleaner scavenger tails range from 0.8% to even as high as 2%Cu. The iron in the feed ranges btwn 10%Fe to 12%Fe.

David
1 year ago
David 1 year ago

+ Nick, what P80 do you regrind to?

Use the Social Share Bar on the Left. Tell everyone you can about https://www.911metallurgist.com/metallurgy/ It's FREE & GOOD.

Nickbob
1 year ago

P80 @ 38um at the regrind.

David
1 year ago
David 1 year ago

Have you ever operated for multiple days without a regrind on? What results do you get then?

Have you ever done laboratory flotation tests without regrind?

Do you add collector in your regrind (or just after)?

Use the Social Share Bar on the Left. Tell everyone you can about https://www.911metallurgist.com/metallurgy/ It's FREE & GOOD.

Nickbob
1 year ago

Dave, thanks very much. We have never operated without regrind on. Test that I have done don't include regrind. We don't add collector in regrind. Not even after. Collector and frother are added at the ball mill cyclone overflow only.

David
1 year ago
David 1 year ago

OK, you therefore have MANY options/possibilities to increase your copper recovery:

  • Eliminate (by-pass) the regrind mill
  • Add collector to the regrind mill
  • Change your frother to stronger W31
  • Change your primary collector to PAX
  • Switch to closed circuit cleaning by returning the Scavenger Cleaner tails to the rougher feed

if this was my mill/plant; I would immediately turn off the regrind mill.

Your cleaner circuit loses are killing you. In a stable circuit, your tails should always be under 1% and closer to 0.5-0.7% 

+ Do you have CaO Lime anywhere in the circuit?  What is your rougher pH?

PS: Am waiting for you on https://www.911metallurgist.com/grinding/ball-mill-cyclone-overflow-p80

Use the Social Share Bar on the Left. Tell everyone you can about https://www.911metallurgist.com/metallurgy/ It's FREE & GOOD.

Nickbob
1 year ago

Hello Dave,
Thanks very much for your advice. I very much agree with you. I will try this and will give you feed back. I will catch up with you https://www.911metallurgist.com/grinding/ball-mill-cyclone-overflow-p80 sooner than later.

Craig Lockhart
1 year ago

Hello Gents,
In my experience, I have found that it is not uncommon to employ primary grinds beyond industry norms when treating high-grade copper ores - the incremental additional recovery that can be gained is worth the additional energy and/or effort (Continental Mine (U/G), Fierro NM, 1.8% Cu- 100 microns; New Afton Mine (U/G, Kamloops, BC, 0.9% Cu 0.7 g/t Au - 130 microns). I would suggest targeting a grind of ~130 microns to test the theory, however this may require a temporary decrease in grinding rate. If you find success at the finer grind, you may want to re-purpose your regrind mill for tertiary grinding your primary cyclone overflow - a secondary cyclone sending the underflow for a single pass through the mill (open circuit) if the mill power is 350 hp or less, or if you have more hp you can try closed circuit. If you have already shut down/by-passed your regrind mill to improve recovery, the finer primary grind will also help restore some of the lost concentrate grade.
I agree with the lime addition and closed-circuit cleaner scavenger tail recommendations. Lime can improve flotation kinetics, reduce consumption of frother and collector, and improve concentrated grade if applied in quantities sufficient to depress pyrite. Your scavenger tail should not exceed half of the head grade - if it is higher, then cleaner capacity needs to increase or tail needs to report back to the rougher. It is not necessary to send the scavenger tail to the head of the rougher bank - you can introduce it mid-way down the rougher bank if you are tight on rougher retention time. Side-benefit - your metallurgical accounting is also simplified.
FYI - Copper recovery at Continental increased more than 2% when tertiary grinding was implemented for a reduction from 150 microns to 110 microns. (2 ea. 10' X 6' X 200 hp Denver ball mills in closed circuit @ 250 tph). New Afton implemented tertiary grinding in 2015 (VTM 3000 @ 600+ tph) for a reduction from ~200 microns to 130 microns, and also achieved >2% increase in rougher recovery.

Please join and login to participate and leave a comment.

BUY Laboratory & Small Plant Process Equipment

We have all the laboratory and plant equipment you need to test or build/operate your plant.

ENTER our Mining Equipment' Store

We Sell EQUIPMENT for all types of Mineral Treatment PROCESSES and Laboratory Testing needs

Have a Mineral Processing QUESTION?

Come in, ask your question

911Metallurgist Community Forums

Talk to other metallurgists and be helped.

Need ENGINEERING Services or Plant TROUBLESHOOTING?

We can IMPROVE ALL PLANTS / Mineral Processing Engineering & LABORATORY Ore Testing

911Metallurgy Engineering

Contact us for process engineering, metallurgical investigations, plant optimization, plant troubleshooting, needs. WE “FIX” METALLURGY.