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

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

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Low Gold Recovery: Adsorption stage problem in batch process (3 replies and 1 comment)

J
Jeffreybch
6 years ago
Jeffreybch 6 years ago

Hi,

My name is Jeffrey, I manage a little benefitiation plant in Costa Rica.  We concentrate artisanal tailings (gravity-flotation,which works well) and later we remove the gold (problem).  We produce gravity concentrates in the order of 150-500 grams per tone and flotation concentrates in the order of 30-100 grams per tone.

We are having difficulties in the adsorption stage of our batch process.  Which consists of 4 small pachucas of 1.300 L each, working individually, agitated by a positive displacement blower.

Our current recipe is:

  • Particle Size: 80% minus 200 mesh.
  • Density: 35% solids.
  • Solids: 350 Kilos per batch.
  • Liquids: 650 Kilos per batch.
  • Cyanide: 3 grams per Kilo of concentrate.
  • H2O2 (peroxide): 200 grams.
  • Carbon: 25 Kilos.
  • Time: 24 hours.

I am getting terrible high tailings.  At some point I was agitating with a compressor and according to my experience I was short in air, but things were more or less under control, but since I upgraded the air by using the blower, my results decreased significantly.

Please help me, all advise is appreciated.

Kind Regards,

J.

T
Todd H
6 years ago
Todd H 6 years ago

Dear Jeffrey

There could be a lot of reasons for the problem with extraction such as:

  1. These gold is locked inside the sulphides/quartz - grind size
  2. There is not enough oxygen
  3. There is not enough cyanide
  4. The leach time is too short

Keep in mind that the tailings you are processing can change over time as you move to different area in the pile.

Questions:

  1. Can you do a lab bottle roll test to confirm gold recovery? Use the same conditions as the plant - test retention time, cyanide dosage, use of H2O2
  2. You can just releach the leach tails in the lab to see if more gold is leached
  3. Check your particle size to confirm the right specs are being achieved
  4. Can you measure the dissolved oxygen in the leach tank with a meter - need above 4 ppm better closer to 6 ppm (depends on altitude)
  5. H2O2 - why are you adding it, where are you adding it - it destroys cyanide as well as adding oxygen - tough to balance dosage.  If added as part of preaeration it can be effective
  6. What is the final free cyanide level after leaching
  7. What is your pH - what modifier are you using
  8. What are your solution losses - carbon fouling could be an issue

I would start with a lab test on the material to see where the problem lies.  I don't think air is your problem if the pachucas are remaining agitated you should have enough air. 

Is the air clean and oil free - I have had issues with compressed air sending oil to the leach which fouls the carbon.

Let me know what options you can use to analyse and then I will follow up.

Regards

Todd Harvey - Global Resource Engineering http://www.global-resource-eng.com

R
Richard S
6 years ago

I agree with the suggestions above. As a plant test you might start by cutting back on the H2O2, while providing oxygen it also destroys cyanide. Checking your cyanide levels in the liquid phase of the slurry and the dissolved oxygen levels will be most helpful in giving you direction.
Regards, Richard

T
tesaygo1
6 years ago
tesaygo1 6 years ago

You have high grade concentrate. I do suggest that you need to roasted it so those sulfide will be oxidize, then add the dosage of NaCN of your even 8g/liter of H2O, just to make sure that you can dissolve all gold on it. Anyway you can also recycle the cyanide solution so dont dispose it after leaching.

H
CA
6 years ago
CA 6 years ago

Jeffrey,

I am in Central America and have been working on artisinal tails for a few years now.  You need to determine if the gold is going into solution via atomic absorption.  If you don't have these facilities, I can get them done for you if you are able to send me the samples.  You need some baseline data to determine where your problem is.

Is your carbon new?  It may be leaching fine but not entering the carbon. 

PM me if you would like to chat.

Regards.

 


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