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Bulk flotation vs. Selective flotation (14 replies and 1 comment)

9 months ago
Subhash-Kumar-Roy 9 months ago

How is Bulk Flotation different from Selective Flotation?

9 months ago
Sudhirkumar 9 months ago

Case study-1

For Copper and Lead flotation:

We need to float both minerals 1st. We call it Bulk flotation. Then this bulk concentrate will go to Cleaning stage where we depress Copper, and float Lead-This process we call selective flotation.

Case study-2

For Zinc and Lead Flotation.

Here we depress Zinc and float Lead-This is called selective flotation.

Case study-3

For Zinc and Lead flotation.

Here we faced problems in lead and Zinc circuit. We decided to solve this problem by floating both Zinc and LEAD together-This we call bulk flotation.

For any problems in mineral processing for A to Z solutions I do consultancy on net for nominal charges. 

Kumar Choudhry
9 months ago
Kumar Choudhry 9 months ago

This is also true for Cu/Ni, Cu/Zinc and Cu/Moly where a bulk float is done where you try to collect/recover as much of all minerals as possible. The selective flotation is done on the bulk concentrate where one mineral is depressed with chemicals and the other is floated. There is always some cross contamination in each concentrate - i.e. it is very difficult to get perfect separation in the selective float.

Tarun Karakoti
9 months ago
Tarun Karakoti 9 months ago

Both of you have captured the essence of the differences.

Bulk flotation is often employed for recovery of gold when present with iron sulphides such as pyrite or arsenopyrite. It is usually about decreasing the mass for further treatment, such as leaching after a regrind.

Copper and molybdenum is naturally a bulk float, and provides an example of the problem of separating minerals that have already floated. Very severe conditions are required, such as high levels of NaSH, to depress the copper. So where it is technically possible, selective flotation is preferred.

Classical selective flotation is the Cu/Pb/Zn separation where each mineral is floated separately usually copper, lead (depends on copper: lead ratio) and zinc - usually while depressing pyrite.

9 months ago
Sudhirkumar 9 months ago

Gold in general is available as native form. Native gold cannot be floated. 

Since pyrite is FeS it can be floated. If Gold is in interlocked form with gold then it is natural flotation. Bulk word is used for two different separate (physically) minerals but not interlocked or in solid solution with each other.

When we float Lead- silver associated will also get floated. But we don't name it bulk flotation. Similarly when floating Zinc-cadmium is associated. Here too we call single zinc flotation. Any mineral which cannot be separated physically is not used to call as bulk floatation.

Please confirm in your case what is true. Is gold and pyrite can be separated physically or pyrite is in solid solution or interlocked stage in fine form. Can we not separate pyrite physically using its specific gravity property, to save chemicals and long process of leaching?

Can you send flow sheet of the process to understand it better for more suggestions and improvements?

9 months ago

hmmm.... Native gold can be floated.

Sandeep Bisht
9 months ago
Sandeep Bisht 9 months ago

Your first point is incorrect. Native gold can be floated, given the correct conditions it floats quiet well.

I guess point 2 is covered in comment that you are trying to recovery as much of the minerals (in this case pyrite / aresenopyrite) as possible. Your grade is of secondary consideration as recovery is the target.

Points 3 is a little off the mark. Bulk flotation is where a group of floatable minerals are targets together for maximum recovery whereas selective (or differential) flotation they are targeted sequentially with one of the minerals being depressed while the other floated. Usually when they are floated sequentially grade is of a concern. From my experience in lead (galena) floats the silver is generally an inclusion in the matrix of the galena and thus not separable by flotation so not classed as a bulk float.

Sachin Prakash
9 months ago
Sachin Prakash 9 months ago

Agreed to all your above comments on definition of bulk and selective flotation.

Every ore is having valuable minerals, trace minerals and contaminants. Floating two or more valuable minerals (traces or interlocked particle having ignorable view) at a time and producing bulk concentrate is a bulk flotation.

Selective flotation is floating single valuable mineral at time and depressing the other.

The floated mineral is further subjected to single or multi stage cleaning using depressants and pH modulators to achieve a point on Con grade -recovery curve for that particular liberation size. One can’t nullify presence of Co valuable mineral (Known as misplacement), traces and gangue material completely but can be reduced to possible extent.

The existence and the use of bulk flotation came into picture after getting successful pyromettalurgical technology to extract different metals separately from the group of beneficiated minerals. ISF in Vedanta- India extracts pb, zn, ag, cd, bi, and etc. from galena, sphalerite, and other respective sulphide ore. The separation of metals from molten is on density basis. Without this one is compelled to go for selective floatation where economy depends on many fine controls on grinding and etc.

The few advantages of bulk flotation are as follows.

Maximum recovery can be achieved. Subsidies the effect of interlocked un-liberated particle (Valuable mineral to valuable mineral) to some extent. Little coarse grinding can be manageable, so slimes generation is reduced, increased recovery is materialized.

The grinding is a complex operation and one can’t achieve prompt liberation grind size when different minerals are present in the same ore have different hardness. While liberating one valuable mineral, slimes of other valuable mineral are generated like Moly- copper and etc.

Capex can be reduces as high volume (less in number) flotation cell can materialize the same recovery. No. of cleaning stages are reduced.

OPEX can be reduced as the consumption of frother, collectors may be reduced. Cost on Depressants and pH modulators may also be reduced significantly.

Agreed native gold floats. Read in Denver's Mineral processing hand book that a unit floatation cell floats flaky, coarse, native gold particles operated at 40 % solids density installed after mineral jigs.

9 months ago
Sudhirkumar 9 months ago

Please see RD mines bulk flotation commercial operation during 1995 to 1999. I once changed to bulk Pb-Cu production and sent to smelter. My R&D was all about this subject. Many times suggested the smelter for Pb-Zinc, but there was very poor response. My suggestion is try once again but with column cleaning. Simple Bulk Pb-Zn rougher and cleaning in column. Heavy expenditure on OPEX can be saved. May be 50% savings! You talk to smelter to accept. Like

The process of bulk flotation depends on down line operation. For hydrometallurgy it is not correct. It works only for pyrometallurgy.

How gravity concentrators work for very fine ore particles at 1 micron to 10 micron.

Sachin Prakash
9 months ago
Sachin Prakash 9 months ago

•Agreed that 1 to micron material can’t be separated efficiently with gravity separation. The last effective size of separation I have done in 30 micron +_ 2 Micron in Multotec spirals for hematite ore.

•Vedanta shifting from pyro metallurgy to hydrometallurgy in later stages expansions I suppose, May be the graphite- mica contaminants are one of the reasons.

9 months ago
Sudhirkumar 9 months ago

Good to see your enthusiasm:

Good you have worked with iron ores at 2 microns on spirals. Please send report.

Graphite in ore:

When I was in RDM I did several labs and pilot plant tests for graphite removal a Multi gravity separator.

Mozzly hydrocyclone separator! Due to trash present in ore these tests failed.

But now I have designed one rotating trommel screen for 500 micron cloth to remove trash form slurry. In two plants it was used and found most successful. Yes both MGS and MOZZLY will work wonders for Graphite. See RDM old reports.

You need any help from me I am here to GUIDE and advice you, if you send data. Send your problem with all details on size, assay, Graphite%, etc.

Can we try FLASH FLOTATION once again? I failed due to instrument problems. Spiral is ruled out for Pb Zn processing.

Sachin Prakash
9 months ago
Sachin Prakash 9 months ago

It's 30 plus or minus 2 micron, i mean 28- 32 micron range please, not just 2 micron. I haven’t seen 2 micron mineral normally separated efficiently anywhere.

9 months ago
Sudhirkumar 9 months ago

Lead mineral is too brittle and gets ground very easily. This is the reason and my practical experience which made me to speak that spirals will not work. But it is not correct until unless we try and prove. Try it find solution.

I have operated flash flotation. I am confident it will solve problem with mozly cyclones.

Till date no one has tried column flotation, with froth bed washing. You may try and see. It is a good technology. My sincere suggestion is for bulk and column cleaning.

Raje Singh
9 months ago
Raje Singh 9 months ago

RDM ore contains graphite which can be depressed with nigrosine. It was proved lab tests and presently using in plant.

9 months ago
Sudhirkumar 9 months ago

You have both Hydrometallurgy and Pyrometallurgy smelters. Both need feed of different nature. You can take advantage of both processes. The new technology will have cost saving and increase in recovery.

•Do column flotation of bulk in normal ckt. Clean it in column to reduce graphite and silica.

•Bulk Pb-Zn- Depress Zn using ZnSO4 and float Pb. Send Zn for hydrometallurgy and Pb for pyrometallurgy. Or try Spiral gravity separator.

9 months ago
Amar 9 months ago

The different between Bulk Flotation and Selective Flotation is: In Bulk Flotation, in the concentrate you have all ores that you have in your slurry. In Selective Flotation by the action of reactive you can have in the concentrate one ore that you want. The quality of concentrate its better than Bulk Flotation.

When you start a process, you start whit Rougher Cells (could be Bulk Flotation) then you go for a Cleaner Cell (could be in this case Selective Flotation). All depends what you want concentrate, the ore, etc.

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