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Cleaner and Re-cleaner Flotation Performance (11 replies)

Kumar Choudhry
9 months ago
Kumar Choudhry 9 months ago

I have been assigned a project to investigate and optimizeflotation cleaner and re-cleaner performance. We have conducted surveys around cleaner and re-cleaner circuits and have found the following:

  • Cleaner circuit recovery is better than re-cleaners
  • The upgrade is better in the cleaner circuit compared.
  • There is enough residence time in the circuit so this is not an issue.
  • Mechanically both circuits are sound and there is no issue with impellers, air addition and other operating perimeters are working as per optimized guideline.
  • All copper is associated with chalcopyrite only and iron sulphide is the main gangue material.

Having ruled out the above my focus is now on the following:

  • Looking at size by size recovery
  • Send samples away for mineral characterization
  • Understand gangue recovery
  • Investing what is causing con dilution in re-cleaner con
  • Using SMBS as a depressant and regrind of scavenger concentrate is also employed in this circuit.

I would like to find out what are your thoughts on this and what other approaches could I possibly take to resolve this. The circuit doesn't have any measuring instrumentation hence the air flow, bubble size; rate to con flow etc. cannot be measured.

9 months ago
Obersturmbann 9 months ago

A few points to consider:

•Are you certain that the problem of dilution is truly occurring, or is only that the chalcopyrite is no longer able to float and the pyrite continues to float? This may cause a disproportionate iron to copper ratio in concentrate. It would seem that dilution would be a sceptical issue if you are achieving good performance in the cleaners.

•Have you reviewed re-cleaner pull rates with respect to the mass being fed from the cleaners?

•Is there stage addition of collector in the re-cleaners?

•Have you looked the effects of re-cleaner pH?

•Size by size analysis in both concentrate and tails is likely worthwhile pursing.

Dizzy Flores
9 months ago
Dizzy Flores 9 months ago

Flotation cleaner, is really 'water dilution' cleaning. Too often the cleaner-recleaner slurry density is simply too high.

Example: conc. grade starts to drop, circuit is slowed down, density builds, separation efficiency decreases, and around it goes, until there is a metal dump to tailings.

Victor Bergman
9 months ago
Victor Bergman 9 months ago

Add the water, and check measure the slurry density on each bank tails box.

Bill Rico
9 months ago
Bill Rico 9 months ago

I agree with you regarding dilution cleaning. I think that it is needed to establish a baseline; I mean to perform a series of batch flotation tests (dilution cleaning tests) under ideal conditions to determine what is the ultimate performance you can get with your ore and current reagent scheme. After that I think that you will need to compare the plant to this "ideal" scenario. Perhaps you will find that your problem is not your flotation machines but liberation or chemistry or density, etc.

Helena Russell
9 months ago
Helena Russell 9 months ago

What type of equipment are you running and what your head grade is. I find it strange that you cannot determine some of the most important parameters in your cleaner/re-cleaner circuit. Normally the cleaners will experience overkill as far as reagents are concerned and therefore bubble surface flux and froth depth are two of the most important parameters that you must control if you are "optimizing". Pulp density will also be a problem and dilution will help. It is normal for the cleaners to produce a better upgrade than your re-cleaners. In a Phosphate plant with a head grade of 8% the roughers will upgrade to 28% whilst the cleaners will take it from 28% to 35% and the re-cleaners will take it from 35%-38%. A recovery by particle size will be a good piece of information to have but do include conc. grade for every particle size as well.

If you have rotor diameter and RPM then Rotor tip Reynolds number and Froude number will also be good indicators of bubble surface flux, solid suspension, floatability and net attachment rates. So I think you should put in some effort to obtain these parameters.

9 months ago
Unterstarm 9 months ago

Granulometry is also a significant factor. Coarse and heavy particles are less competitive for the air bubble surface against small and thus lighter ones. Most probably it will be reasonable to separate this coarse fraction from the con to be re-cleaned (in hydrocyclone) and then treat it separately in shaking table - in some cases it really works.

Marshal Dienes
9 months ago
Marshal Dienes 9 months ago

Points 1, 2& 3 will be addressed by a good job of size-by-size mineralogy. You will need to correlate not just the liberation of Cu, but also the gangue distribution by size, with overall performance. People tend to view a mineralogical analysis as mainly a Cu inventory and a global liberation analysis, but if you look at the differences in gangue distribution (e.g. pyrite versus other gangue), and upgrade factors across the unit, you will be able to diagnose more critically than a superficial analysis might indicate.

Dizzy Flores
9 months ago
Dizzy Flores 9 months ago

The behaviour in cleaning can be influenced by prior circuit’s frother.

IF the frother type or addition is too high, the cleaner bubble size will be too small. This will result in poor slurry drainage from the froth phase, and thus carried gangue into the next stages. While dilution will help, the correct frother and multiple frother addition points in the rougher circuits are important.

Adding frother at the start of the rougher only, but adding sufficient to 'carry' to the last rougher cells, usually results in over addition. Much better to stage add frother.

There is also the selection of frother type related to target mineral particle size.

We all could help more, if you add some details of your challenge.

Paul Morrow
9 months ago
Paul Morrow 9 months ago

As a mineralogist I tend to look at some fundamental mineralogical characteristics of the ore, such as the mineral (ore and gangue) liberation by size as pointed out. It might be a good idea to determine if the grade/recovery problems are due to mineralogically inherent characteristics (liberation and locking of the valuable minerals) of a few plant products using automated instruments (i.e., QEMSCAN). If mineralogy is not an issue, then you can look into your flotation parameters etc. A reminder that ToF SIMS is a great tool to determine the surface chemistry, i.e., chemical compounds that might affect flotation.

9 months ago
Standartenfurer 9 months ago

A few questions and suggestions:

•Is the cleaning circuit with recycling of the re-cleaner tails to the feed of the cleaners? If so, what's the recirculating load?

•This has indirectly a large impact on observed stage recoveries in a plant.

•The observed larger upgrade in the cleaners than in the re-cleaners is only due to the rejection of the gangue - say each stage may reject 50% of the gangue in its feed and there is 50% gangue in the fresh feed to the cleaning circuit. For chalcopyrite-pyrite, the fresh feed to the cleaning circuit would grade around 15% Cu, the cleaner concentrate around 21% Cu, and the re-cleaner concentrate around 24% Cu.

•The re-cleaner retention time should be less than or equal to the cleaner retention time. This arrangement works well when recirculating the recleaner’s tails back to the cleaners preferably after some regrind.

•It's good that there are no mechanical issues with the flotation cells. Is this a new plant?

•Is the issue one of not reaching the desired concentrate grade since most of the areas of focus for further investigations are related to the behaviour of the gangue?

Process mineralogy is definitively one of the tools to be used.

Jean Rasczak
9 months ago
Jean Rasczak 9 months ago

How is your investigation going? Have you been able to characterize the feed to the cleaners, the copper lost to tails, or what is diluting the concentrate?

Next, are the upstream targets appropriate? For example if your final con is diluted by pyrite is that because you are recovering a lot of pyrite in the rougher?

I would not mess around with the circuit and depressant. It would be easier to sample from the circuit and do a simple float test. Keep it simple. For example grab the tails add collector see if more floats. Grab the cleaner feed, filter it and keep the water, grind it more, float it with the water you saved. If you sample a few buckets at the same time you can assume they are close enough to each other to compare. Make one con and one tail and assay your target element only. Get the masses accurate. No spilling. This is easy on the budget and gives you a chance to mess about with low impact before you ask for expensive changes. Keep your tests simple and do lots of them with repeats. Repeats are the key. Even if you have no idea what you are doing the mistakes will eventually wash away with enough repeats. A bit of exaggeration but it will do. Once your technique improves you can get more analyses done.

Remember that metallurgists are dirt accountants that make money. If your accounting is sloppy you can't justify the expense. Once you get good you will know how many analyses you can afford to pay back with your gains.

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