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 losses (5 replies and 4 comments)

Irene Ibz
8 months ago
Irene Ibz 8 months ago

Hello,

I work in a plant where there are a lot of carbon losses of about 7 to 9 tonnes per month.. Now I have been given a project to minimize the carbon losses and of course I know carbon is lost due to attrition losses in the agitators, kiln, due to screen leakage and so on but specifically I need to know how to quantify these losses and put them into numbers.. thank you!

Jorge Ganoza
8 months ago
Jorge Ganoza 8 months ago

It is well known that active carbon is lost by attrition and abrasion during the adsorption process, and also when is pumped, transported, screened, burned and regenerated. The first step is to select the right activated carbon, in your case abrasion tests should be included in the evaluation. Abrasion tests involve subjecting the sized activated carbon sample to a wear state. Dry and wet tests are necessary.

In your operation, you should follow the new carbon added in the circuit. You know the weight of the carbon added in the last tank. When that charge of carbon is loaded and removed from the circuit, you can determine the new weight. In this case you can estimate the losses in the adsorption circuit. The same approach can be considered in the next stages, desorption, regeneration, and screening.

It is important to evaluate your equipment. Make sure the speed and mechanical parts are correct. Your study should consider an historical information of the carbon losses to identify any possible change in any period.

Irene Ibz
8 months ago

Thank you so much Jorge! But what about screening?

Jorge Ganoza
8 months ago
Jorge Ganoza 8 months ago

After regeneration, the activated carbon is screened (e.g. 20 mesh) to remove fine particles. The oversize fraction is returned to the adsorption circuit. Considering the fact that you know the weight added in the last tank, you can determine the loss of activated carbon (undersize).

The last adsorption tank could be a potential source of losses if the screen installed in the tank is not correct. The presence of fine particles of activated carbon could pass through the screen opening. 

Irene Ibz
8 months ago

Thanks a lot.. I tried to do some abrasion tests but I doubt the results since the used carbon had high abrasion resistance than virgin carbon... how do u determine your abrasion tests plz

Jorge Ganoza
8 months ago
Jorge Ganoza 8 months ago

In order to perform the dry abrasion tests, 40-50 g charge of dried sized carbon is pre-abraded for ten minutes on a 1.0 mm standard brass sieve of 8” diameter employing a 20 mm stainless steel ball and a rot-tap sieve shaker. The oversize material is subjected to the same conditions for further 60 minutes. Then, the percentage ratio of oversize to total charge is the abrasion resistance,

Wear resistance = [+1.0 mm, oversize/(oversize + undersize)] x 100

Irene Ibz
8 months ago

Thanks a lot Jorge!

Irene Ibz
8 months ago

Hello!

After regeneration I couldn't get the real losses because there are carbon remained in the pre drier and others in quenching tank so it was a bit hard to quantify carbon losses from the kiln but I tried to by pass carbon directly from elution to the sizing screen in the last tank and I did as u said, I got the undersize is 0.42 tones.. but I think it's quite big so that means in every batch or cycle we are loosing that much carbon? Per day we are running 1.5 batches. Or what does it imply?

Thanks...!

Jorge Ganoza
8 months ago
Jorge Ganoza 8 months ago
1 like by Mikhail

In the regeneration stage you should compare the tonnage fed in the process and the tonnage obtained after generation. As you said, some carbon remains in some stages of the process (they represent losses). Considering the fact that it happens every regeneration cycle, you have a source of losses in this process. Regarding the classification process, what is the screen opening considered in your engineering design? In you last adsorption tank there should be a screen, what is the screen opening? You can use it to classify the carbon, the reason is simple, if a particle of carbon is smaller than the opening, it will be reported in the tailings. Don forget that the forum provides only suggestions. 

SIMetallurgist
7 months ago
SIMetallurgist 7 months ago
1 like by David

Hi Irene,

Some more things to try, attach a 20 mesh screen to a sampler and dip it in the launder of your last CIP or CIL discharge going to tails. This will show if you have carbon losses coming out the back end of your circuit. Also check each screen daily for wear, bad seals, and holes to ensure nothing is escaping. The best way to do this is to valve out or block the flow to that screen to inspect it.

When you measure the carbon loading in each tank also weigh the carbon samples to determine carbon concentration per tank. You will know how much carbon was added so you will be able to track the losses. It is best to check inventory on a weekly or even biweekly basis.

Another thing to look for which I have found helpful is carbon transfer pump design and piping design. Minimize sharp elbows and try to use a recessed impeller pump to reduce carbon wear. Hardness and carbon density are also important to consider when selecting a carbon as mentioned above. Good luck and hope this helps.


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