Froth Flotation (Sulphide & Oxide)

Froth Flotation (Sulphide & Oxide) 2017-03-23T09:43:25+00:00
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Depressing of Alumina in a mixed Sulphide Oxide Copper flotation plant. (7 replies)

Sachin Prakash
1 year ago
Sachin Prakash 1 year ago

Our plant is a mixed Sulphide / Oxide Copper ore plant with acid soluble ratio in the feed of 14 to 20%. The ore grade is 1.8 to 2.2% Total Copper. The major sulphide mineral is charcalcite, Chalcopyrite,Bornite and covellite are minor contributors. Major Oxide Mineral is malachite, Pseudomalachite, chrysocolla, azurite and cuprite are minor.

The gangue is composed of mostly argillite.

The plant produces two separate coelenterates from the sulphide and oxide circuit and blends the two to produce combined final concentrate.

The bulk gangue mineral in the concentrate is argillite with most of the alumina while the remainder of the silica is present in the comparatively minor quartz/feldspar.

We have manage to reduce the silica levels by running cells with very high froth depth in final concentrate cells, but reducing alumina has been a challenge. What reagents can you use to depress alumina?

Paul Morrow
1 year ago
Paul Morrow 1 year ago

What is the silica content of each copper concentrate (i.e. sulphide and 'oxide') before they are combined?

I would suspect, depending upon the froth characteristics that the major contribution would be coming from the 'oxide' circuit - which is a sulphidisation operation I presume.

Secondly, the recovery of the argillite would probably be due to entrainment, which about the froth characteristics - is the froth 'sticky' with poor drainage. This type of froth, no matter how deep, doesn't allow much 'cleaning' to occur.

So a first pass, I would be considering a dispersant (e.g. sodium silicate, sodium hexametaphosphate, etc.), running a lower percents solids - both of these, and combinations, can be tested in the laboratory - while I would also look at the frother type - some frothers produce 'sticky' and poor draining froths while others (e.g. MIBC) produce a 'dry', well-draining froth (however testing frothers is really a plant scale experiment).

No doubt there are some other considerations which our learned and experienced colleagues can suggest.

1 year ago

I am puzzled by the indication that using deep froths in the cleaning stages (reducing entrainment) have brought down the silica content in the concentrate but not the alumina content.

A few questions coming to mind are:

Was quantitative mineralogy performed to determine how much of the alumina content in the concentrate is linked to chrysocolla?

Is the argillite in the concentrate coming from the sulphide circuit or the oxide circuit?

Carl Jenkins
1 year ago
Carl Jenkins 1 year ago

Sounds like you have an interesting copper ore to deal with. Unfortunately many questions will need to be raised to gain sufficient knowledge of your system before any potential solution paths might be suggested. However I do advise against adding reagents to any flotation system unless it has been exhaustively tested and researched. I have seen too many flotation operations go down the track of "reagent solutions" only to find they have lost their way altogether, subsequently resorting to "Bucket Metallurgy". One particular operation comes to mind where some 20 reagents were added to a not so complex copper/lead/zinc ore-result? They had no idea what was happening! The mudstones you have could be very difficult to selectively depress but by all means you should be trying to in the lab at least. I don't know what float cells you are using etc, but one thing worth trying is to reduce air addition and reagent addition to an absolute minimum. Some form of de-sliming your flotation feed may also be worth trying.

Sachin Prakash
1 year ago
Sachin Prakash 1 year ago

Thanks very much for your contributions; the major gangue contribution is from the oxide re-cleaner concentrate, followed by Sulphide rougher concentrate, then the sulphide cleaner column.

After running at deep froth depth, Silica reduced from 25 to less 18% on sulphide concentrate, alumina reduced slightly from 8 to 6%. On oxide silica reduced from 30 to 24% and alumina by 1% from 10 to 9%. According to our customer, it is comfortable to treat our concentrate with silica levels of 22%, which we are managing i.e. 18 to 20%Silica combined than alumina of 6% in combined concentrate. Our customer wants <3% alumina.

The type of cells we are using Outotec OK tank cells and for roughing and cleaning on oxide and column sulphide cleaning.

Victor Bergman
1 year ago
Victor Bergman 1 year ago

Have you been using a desliming circuit before oxide or sulphide circuit?

Do you have a grain size distribution of the oxide concentrate?

Argilite grinding may generate a very fine particle size, difficult to depress in flotation, even in column cleaners.

1 year ago

It would be worth estimating if most of the alumina in the oxide concentrate comes from the chrysocolla. The observed tiny reduction in alumina content by using deep froths in the oxide cleaning stage is suggesting that this would be extremely likely.

If the alumina in the oxide concentrate is essentially from the chrysocolla, then short of not recovering this mineral, the most promising area for alumina reduction would be from the sulphide concentrates.

In this last regards, it would appear from your descriptions of the alumina contributors that the rougher sulphide concentrate is forwarded directly to the final concentrate. Cleaning this rougher concentrate could be sufficient to get the alumina content in final concentrate to the desired level.

I would also review the collector levels using in the sulphide circuit - they may be too aggressive leading to the recovery of locked particles less than 10% sulphides in content (i.e. mostly rock!). Regrinding prior to cleaning would minimize the copper losses while minimizing recovery of the non-sulphides.

Carl Jenkins
1 year ago
Carl Jenkins 1 year ago

The fundamental question you have to address is whether the gangue is physically entrained into your concentrate, or whether it is activated by your reagent regime allowing it to float as liberated particles. physical entrainment happens when you are pulling froth too hard (amongst other things) so try to slow down if that is the case (I know a lot of operating models now work on "mass pull" which is OK if you are pulling the required mass-not any mass!!

If you have "down the bank" flotation data this will shed some light on the relative flotation rate of your gangue, if the gangue is floating in the early cells then it probably activated, if it floating in the last cells then it could be a pulling rate issue.

You mention columns, what type of sparging system do you have? If it is the pump/cavitations tube set up then I advise you get rid of it quick!! They create very dense non draining Foam instead of froth.

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