Hydrometallurgy: Leaching in Heap, Vat, CIL, CIP, Merrill–Crowe, SX Solvent Extraction

Hydrometallurgy: Leaching in Heap, Vat, CIL, CIP, Merrill–Crowe, SX Solvent Extraction 2017-04-04T06:57:36+00:00
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Carbon Adsorption Columns (12 replies and 1 comment)

1 year ago
Sudhirkumar 1 year ago

We ran a milling in cyanide CIL plant for reprocessing a gold tailings dump for one and half years. We were achieving 60-70% dissolution in the mill then followed by adsorption in 6 CIL tanks.We are now looking at modifying the process and introducing carbon in column adsorption on the primary classification over flow which is 20-30% solids and grind 80% passing 75 microns. We would also want to increase the mill dissolution to 80% since we noticed this can be achieved. Will then get the other 20% through CIL or depending on the economics might take out the CIL.

The question is on the practical capability to run the carbon adsorption columns in this process.

1 year ago
Oberfuhrer 1 year ago

My question is "why". If you already have a CIL circuit that is recovering your gold, should you not focus on maximising the gold make there? Assuming your CIL is overloaded, and then CIC may be an option.

I am a technical metallurgist and have analysed this problem once, but not actually seen it done. We determined that the CIC with slurry is not practical as there are viscosity issues, sanding of the bed, and the need to screen out the slurry you may as well have a CIL circuit which is proven technology.

CIC needs a thickener to produce a clean solution, and there are examples of this flow sheet available in the literature and on the internet (Nevada from memory). I have used CIC columns at three different plants and they are very efficient for gold recovery as well as being low power and small footprint. 

Marshal Dienes
1 year ago
Marshal Dienes 1 year ago

As mentioned earlier for Carbon column you will need clean solution - an overflow of 20-30% solids on your primary classifier overflow will foul the carbon very quickly.

If you want help designing an operational circuit send me an email, but to do any circuit balance will require a fee for engineering services

1 year ago
Sudhirkumar 1 year ago

The reason why are evaluating CIC as an alternative option is because we are looking at processing different small dumps in various locations and we want to develop a modular mobile processing plant for that. The carbon columns sort of fit in that model well.

Victor Bergman
1 year ago
Victor Bergman 1 year ago

You both have got it right.
You may achieve loadings on your carbon in dilute slurry but at one point you have to decide to move out the carbon for elution- when is that? At what loading! Do you bypass the column? Do you stop for that? Cost of that versus what you have already? This is tricky for sure-

I will concern myself with the fact that you want to treat ores from different locations? Ensure that they all demonstrate similar metallurgy and leaching characteristic before you invest too much into a modular or generic plant.

1 year ago
Standartenfurer 1 year ago

You didn’t mention the tails you are treating, Heap leach Battery or CIL/CIP tails the Gold recovery will vary slightly.

With the CIL/CIP being the most difficult! Please keep in mind that all these tailings will have various amounts of carbon distributed throughout the dam. The very old dams will have plenty, from old pachukas tanks with only one screen per tank, carbon loss was extreme in some instances. Even today some plants not only lose fine but coarse carbon as well.

These tails have been milled. So may I suggest a scrubber/wash plant to loosen the ore and carbon? As you know the layers have been distributed horizontally over the years, so the various ores and carbon will take from these tails dams vertically to be fed to your operations. This eliminates a constant ore type.

I once saw an operation that concentrated on just carbon recovery from old dams, it was years ago and they told me nothing, but they seemed to keep operating as we know, and Carbon is Gold.
Just thought I’d add my bit.

1 year ago
Sudhirkumar 1 year ago

Most of these tailings are from small vat leach operations and are mostly oxidised. That sort of eliminates the carbon problem.

The idea behind the modular plant is not to make it "generic" but mainly "mobile" to able to reach the dumps. In our case it will be cheaper to move the plant than moving the ore, but yes some metallurgical test work is always done first.

Sugar Watkins
1 year ago
Sugar Watkins 1 year ago

If the old dumps contain sulphides associated with the gold, best to keep the CIL. Having said that, if everything is oxidized and you want to use CIC, then a small clarifier could be included with your mobile plant (Lamella clarifier), depending on the tonnage you design the mobile plant for. Sounds like the old dumps would be small and then a Lamella Clarifier would work - once again -TEST the whole process to see where the bugs are.

Rahil Khan
1 year ago
Rahil Khan 1 year ago

I agree with everyone above. You need to know the cause of high tails and try to optimize the CIL circuit. Once the solution is not clean; after bedding occurs the solution will find a "channel" within the column on its way to the next column and down the stream to the last column. This means the bulk of the column volume becomes a dead zone hence poor adsorption will result. This will be a result of low residence time and poor solution distribution in the adsorption columns.

Maya Rothman
1 year ago
Maya Rothman 1 year ago

Use a small filter in the cyclone overflow so you can treat the preg solution using carbon columns then you will have the opportunity of to re-pulp or to use big bags to send the ore to the CIL plant or final disposal. It will also help you to recover as much as you can of the solution. Regarding recovery try to maximize circulating load (residence time), you can also evaluate to include a small centrifugal concentrator in the cyclone underflow or a jig a pre concentrator (before the plant) depending on the ore characteristics. To add an oxidant can also help but have to evaluate the benefit vs. the higher media and liners consumption rates.

1 year ago
Obersturmbann 1 year ago

Your question is two folds increasing the recovery in the mill. The only way I know to increase dissolution rate in the mill is the dissolved oxygen content. Peroxide works well and it is also a proven method. Concerning CIC well I hate to think of what will happen in the columns if let say the power goes off or a pump is failing. You will need a lot of pressure to lift back the settled materials. Remember the carbon will have to fluidise constantly so the carbon is always in suspension by carefully adjusting the flow of the pulp. Innovation is good thing but not if it is just for the innovation you may well encounter all sort unforeseen problems.

Concerning the terms of CIP and CIL there is some confusion in lot of people minds. A real CIL circuit is when cyanide and lime or caustic soda is added in the carbon tanks only. If you mill in cyanide and then send the pulp to the agitated carbon tanks then you have a CIP circuit though you still dissolve more gold into the carbon tank. CIL is only useful when you have preg robbing materials in your ore otherwise CIP is far better as you get a far better loading on your first thanks and not spreading the gold down the line.

1 year ago
Sudhirkumar 1 year ago

Anyone with an idea if it will be possible to use flocculants or coagulant if we use a lamellar clarifier! Will this have any effect on downstream processes especially CIS column adsorption.

1 year ago

You can use floc and coagulants with lamellas, and as with the use of any thickener ahead of a carbon process - the organics will adsorb onto your carbon, but usually nothing that a normal regen process can't take care of.

Lamella clarifiers can be quite sensitive beasts, and are reasonably expensive - they are usually used in wastewater or pre-membrane applications, not so much of full slurries
- if you are considering going the CIC route you might want to have a look at just the usual range of thickeners, and if you need exceptionally good clarity into your CIC then a conventional or even pinned bed clarifier might prove to be more cost effective, and less likely to provide operation problems.

1 year ago
Oberfuhrer 1 year ago

Activated carbon has a high affinity for charged molecules; and as such would probably adsorb flocculant. If you have a good regeneration circuit this will not be a problem.

As for the remainder of the circuit, flocculants shears relatively easily and should not present any problems with the leaching circuit. This has been done in the past and as always, with a good metallurgist and a good operations team there should not be any problems.

I would use a conventional thickener in preference to a lamellar thickener for plant modifications on a limited budget - stick with conventional technology as much as possible; as there is a reason it is used it works.

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