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Batch Flotation Tests (18 replies and 2 comments)

Bill Fraser
10 months ago
Bill Fraser 10 months ago

If you are doing batch flotation tests in the lab for evaluating reagents, grind size effect and grade/recovery improvement, does the Percent solids have to match plant Percent solids or it doesn't matter. Also if can refer to me to notes/text books which provide more detail information on Batch flotation testing, it would be appreciated.

Bill Rico
10 months ago
Bill Rico 10 months ago

Percent solid doesn't affect grade/recovery of the process and it doesn't need to be the same as plant Percent solid, however there're plenty of study which show this fact, S. K. Kawatra Chair and Professor in Department of Chemical Engineering of Michigan Technological University had published the study of forth flotation through Fundamental Principles of it, you can find it easily I guess.

9 months ago

Rico, i thought in one way or another %solids would very much affect flotation of minerals and so the recovery and grade. This parameter, if not attended well, can make you fail to flot the mineral even if you will have balanced the reagent addition well. E.g If you are operating at P80 of 150microns, then you find that you are doing far less P80 then you can not flot the mineral and so this will definitely affect your grade and so your recovery.
How about that?

9 months ago

Thanks for you input Nicomedk,
Here is a test group on flotation density and is impact you make like to review and comment on https://www.911metallurgist.com/blog/effect-of-flotation-cell-size-laboratory

Bob Mathias
10 months ago
Bob Mathias 10 months ago

Percent solids can potentially affect significantly the grade/recovery curve. It is very common that low density slurries give better flotation response (high grades) particularly in flotation systems containing significant amount of liberated hydrophilic unwanted mineral particles. The froth in any flotation system contains water that in absence of wash water is essentially the slurry in the collection zone, the more dilute the slurry the lower the entrainment of liberated hydrophilic gangue therefore the better the grade. The experiment to determine if percent solids affect your particular system is simple and it consists on performing at one stage batch test at current plant density and compare that to three stages of cleaning starting the first stage at low density (<10% solids by weight). Below is the reference of a paper describing this technique:


Dizzy Flores
10 months ago
Dizzy Flores 10 months ago

It is about entrainment and some operations need to lower the percent solids in the cleaning circuit to achieve the grade that they are after.

Generally good practice to operate at the same percent solids as the plant. There are not many reasons why you wouldn't.

If the system can handle it, a 'dry' frother should be used e.g. MIBC which minimises entrainment. Note that frothers really need to be tested in the plant and not in the laboratory.

Should also use the same water (process water make-up or totally fresh) and the same chemical parameters, particularly the ORP.
Once you have sorted out your reagent screening and grind size studies, and have settled upon the best combination, I would suggest duplication tests (natural variability).

You should test any rougher/scavenger benefits through to cleaning - depends upon the plant flow sheet and the commodity, but at least two stages and possibly more (cf. molybdenum - up to 10!) and undertake Locked Cycle Testing (LCT) to demonstrate the potential improvement in the plant.

You will need around 8 to 16 kg for a LCT depending upon the charges (1 or 2 kg charges).

There is lots to learn about doing flotation test work, scrapping rates, aeration rates, washing down, taking samples, etc. - including recognising what is going on (e.g. 'fizzing' froth - excessive particle hydrophobicity, etc.)...that is why i leave test work to the master float technicians - from whom i continually learn and I reckon that I know a little bit about flotation test work for most commodities.

Carmen Ibanz
10 months ago
Carmen Ibanz 10 months ago

But by not affecting grade/recovery, i mean that when your tests is due to considering the reagents evaluation. Of course, the more dilute slurry is, the better grade will obtain, i couldn't agree more on this.

Ace Levy
10 months ago
Ace Levy 10 months ago

When doing batch flotation tests, it is more like you are simulating your rougher flotation bank. You would normally target your primary mill grind or rougher feed grind e.g. 55% passing 75um. Also it helps to float at the density close to your rougher feed density. Even the residence time, you should make it closer to your plant rougher bank residence time.

I personally prefer to pull three concentrate as it allows me to model for fast floaters, slow floaters etc., and it at least gives me a curve not a straight line from two points.

Carl Jenkins
10 months ago
Carl Jenkins 10 months ago

Remember the focus as per original request is "If you are doing batch flotation test in the lab for evaluating reagents". As long as density is close enough but kept the same for all the batch tests, it should not really matter.

Marshal Meru
10 months ago
Marshal Meru 10 months ago

No one is correct----

WeightPercent solids:
Different minerals have different weightPercent solids. If you want to know correct weightPercent solids then you need to do optimization test. Do testing for 10, 20, 30, 40, 50 % solids, draw the graph and find optimum weightPercent solids at higher grade and recovery. For Metals in hard rock 40% is optimum. For iron ore it is different. Presence of slime also play a major role in flotation.
Similarly for Grind size.

Zander Barcalow
10 months ago
Zander Barcalow 10 months ago

Pulp density is an important variable in flotation, unless there is a very good reason for not testing at the same density in lab and plant, it should be the same.

Pulp density affects a number of parameters, including;
1 Air distribution and holdup in flotation cell.
2 Reagent solution concentration.
Additionally and very significantly, pulp density affects residence time when comparing lab and plant performance, if you perform your lab tests at a different pulp density to the plant then you cannot correlate the relative flotation residence times.

Marshal Dienes
10 months ago
Marshal Dienes 10 months ago

I agree with the fact that pulp density is an important variable in flotation and, hence, it can’t be left out of the set of variables that need to be studied.

Water and air have an ideal concentration in a flotation cell, at which maximum metallurgical performance can be reached. Water and air are 2 of the reagents in a flotation cell and their concentrations play a role on the metallurgical performance.

In the past I have recommended that one should never develop flotation tests by moving one parameter at a time. This is because the partial concentrations of reagents change (Remember, water and air are reagents) causing chemical reactions to develop in a whole new way. When one changes only one parameter one can have too much or too little of that reagent in the new scenario and one influences the chemical reactions balance.

So let’s say, for example, that you had perfect concentration of collector at 30% solids by weight. Remember, there will be a chemical reaction of this collector with air, water and with the ore. Now let’s assume you went up with the slurry percent solids to 40% by weight. Now you have less water so part of the collector that was in an interaction with the water should now be available to do other things. But you didn't change the collector dosage, right? How do you know how much collector do you need now?
Some people says the collector must be added based on mineralogical species availability, other say that the collector needs to be added based on the water you add to your system. The thing is that no one knows how the collectors or modifiers or the other reagents interact in the flotation cell. This is a fact and this fact is very dynamic in a plant environment where the ore changes every minute (Some people may believe that the ore feed to a mill has a more homogeneous nature. If you believe this I would suggest you take a feed sample every 30 seconds in the flotation feed. Measure the grade of 30or 60 samples taken at 30 or 45 seconds interval. See how the grade changes. If the grade changes then more things also change)
Please, remember: a DOE can be very helpful to screen flotation variables and then to optimize them.

David Kano
10 months ago
David Kano 10 months ago

Lab testing is very difficult to match industrial applications however has a high influence in performance.

Paul Morrow
10 months ago
Paul Morrow 10 months ago

The short reply to your first question is yes, the pulp density (Percent solids) is an important variable in the flotation process and the laboratory tests should be best performed at the same pulp density as in the plant.

As for your second question, if I remember well, the book "Mineral Processing Technology" (B.A. Wills, Pergamon Press) has a section on batch flotation testing. Also, Cytec's "Mining Chemicals Handbook" also briefly cover the basics of batch flotation testing (and is available as a PDF from Cytec's site).

Finally - it appears that you have limited exposure to batch flotation testing. In this case, I would strongly recommend that you get your hand on the operating manual for the flotation cell you will be using and study it - they describe the workings of the flotation cell from a practical view point.

Once you a few tests have been performed and it has been ascertained that the reproducible results can be obtained, then more sophisticated tools (such as DOE) can be explored.

Tony Verdeschi
10 months ago
Tony Verdeschi 10 months ago

There has been a lot of discussion and all relevant and I may be repeating some but these are my initial thoughts....

I would look at the feed grades to your flotation circuit first, are feed grade variations large or small? What is your particle size distribution in your feed material and how consistent is it on the plant as in what is your P80 range?

If you use 10% solids compared to 40% solids for your batch tests your mineral content is different. Also if you have different P80's for the same Percent solids say P80 of 45um compared to P80 90um your mineral surface exposure is different, which all affects a number of parameters mentioned previously e.g. dosages requirements, ORP, dissolved oxygen content etc. Plant trials may also need to be conducted. However coming back to the question you asked I would definitely keep my Percent solids fixed for all batch test work and have it as close as possible to the plant Percent solids while playing around with the other parameters.

PS: Make sure you have a reproducible baseline batch flotation test to start off with for your current plant setup.

Alan Carter
10 months ago
Alan Carter 10 months ago

Flotation Lab tests:It gives sufficient knowledge about operating parameters and their effect on grade and recovery. Weight Percent Solids is only one parameter of flotation. On similar lines you need to optimize other parameters too. Plant is designed based on pilot plant tests. And follow all NIT during operation too. If you face problems you need to go back to pilot plant and redesign parameters and then apply to your plant. If you have a degree in Mineral processing then it will be easy to change parameters in plant directly. No suggestions will work. It will give a guide lines to work in right parameters value. You need to struggle and optimism parameter. Flotation is a complex subject to understand. It operates on many permutations and combinations of following parameters:

  1. Particle size
  2. Wt% solids,
  3. Sub-micron weight Percent,
  4. Chemical quality and strength
  5. Aeration system used, Qty and pressure
  6. Water quality and pH,
  7. Cell design,
  8. Froth bubble size.
  9. Froth bed height,
  10. Residence time,
  11. Pulp viscosity,
  12. Instrumentation used,
  13. Operator training and skill.
Maya Rothman
10 months ago
Maya Rothman 10 months ago

Have a look at this article on Laboratory-Flotation-Testing-Procedure

Victor Bergman
10 months ago
Victor Bergman 10 months ago

The weight Percentsolid is one of flotation parameter that must be optimized but in general the optimal weight Percentsolids vary 30 to 40% max.

Helena Russell
10 months ago
Helena Russell 10 months ago

While 30 to 40% solids by weight my work for some ore types it may not work well for other ore types or for some rougher or for some differential flotation processes

I know ores that will not float well even at 10% solids because of viscosity issues.
I would say: make sure that you don't leave the slurry percent solids out for the variables you need to optimize from your ore types.
Take decisions based on data.

John Koenig
10 months ago
John Koenig 10 months ago

I think Lab testing is an art. You need to learn many things and optimize many parameters. If you want just Weight Percent solids it is wrong. Different minerals have different densities. Better you do experiment on Volume Percent solids. Yes it will match your plant provided you follow all parameters of Plant in Batch. Or else it is just understanding to know how your mineral behave at different conditions. You may apply slowly in plant with minor incremental changes and see reaction. This is how we did for 24 years in lab.

Sugar Watkins
10 months ago
Sugar Watkins 10 months ago

The Percent solid is an important parameter in flotation. You need to simulate the plant condition as reagents dosage is based on g/t so you need to know the dry tones in a given float cell to correctly calculate dosage or else you over or under dose and when it comes to plant trial, the parameters will be totally different and one may conclude wrongly.

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