Pyrometallurgy: Roasting, Smelting, Refining & Electrowinning

Pyrometallurgy: Roasting, Smelting, Refining & Electrowinning 2017-04-21T02:33:06+00:00
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Waste Elution Acid into Leach Tanks (10 replies)

Kumar Choudhry
1 year ago
Kumar Choudhry 1 year ago

The practice of discharging waste acid after acid was in elution into leach tanks as a form of disposal is being practiced. Is this a normal practice or it has severe impacts on the leaching kinetics as well as the leaching parameters. Please educate me on the harmful and good effects of this practice in CIL operation

Dizzy Flores
1 year ago
Dizzy Flores 1 year ago

The fear is that there may be gold in solution, thus it is standard gold plant practice to transfer waste and spillage back one process stage, after the pH has been reduced by rinsing the washed carbon. However, you are right the acid can affect the pH of cyanidation, if this becomes significant then you may want to use some tailings solution to counteract the acid. Unless you repeatedly confirm that there is no dissolved gold in your washings then I'd advice still putting them back into the final Leach tank.

Kumar Choudhry
1 year ago
Kumar Choudhry 1 year ago

Okay. In that case we cannot say there is an impact on the tank leaching kinetics? Also when you talk about tailings solution what categorically are you referring to as that?

1 year ago
Unterstarm 1 year ago

You could run bottle roll test where you add the waste solution to a bottle and compare it to a normal bottle rolled. Comparing the results you can tell if you have difference in the leaching kinetics.

Bill Fraser
1 year ago
Bill Fraser 1 year ago

Look at the volume of acid wash solution per hour versus the volume of pulp in the CIL. The acid can be metered in to minimize pH variation

Carl Jenkins
1 year ago
Carl Jenkins 1 year ago

It used to be standard practice to send the acid rinse solution to the tail end of the adsorption train, preferably after the last tank. I doubt there would be benefits to bringing this in further upstream.

1 year ago
Oberstorm 1 year ago

I set-up HCl recycle in several plants by way of distillation of the waste acid to recover HCl of approximately 20% strength that was actually more pure than the technical grade the plant was buying, and also produce lots of calcium chloride (CaCl2) in the process which is great for melting ice if you are in an area where this is needed. In my 14 years working with these HCl solutions, I never found any detectable level of gold in solution by AA to warrant adding it to the carbon containing tanks.

Bob Mathias
1 year ago
Bob Mathias 1 year ago

Spent acid wash solution should never be returned to the process. The pH is low which prohibits any practical level of free CN to be available and without CN there is no Au in ionic form. It only will cost more in pH and CN control apart that causes HCN generation. The spent acid wash is returned generally to tails stream, not to the process. Elution barren solution is always returned to the process.

1 year ago
Amar 1 year ago

The spent acid is metered into the tailings stream following the last adsorption cell free cyanide loss will help in maintaining regulation levels in your tailings & maybe ppm levels of chloride will be observed in tails solution recycle to the plant as a result of dilution & adsorption of chlorides in tail solids; a head's up on chlorides during acidic pressure oxidation several ppm can affect Au precipitation within carbonaceous matrices in the autoclave w/o possibility of recovery.

Zander Barcalow
1 year ago
Zander Barcalow 1 year ago

Send it to the tailings hopper and there can be no risk of HCN generation at the Leach tank and there will be no reaction with cyanide in the area costing money. Don't send it to the last adsorption tank either you'll react with any cyanide that is left there and possible cause problems here as well. Just get rid of it to the TSF directly and eliminate any problems with the process or OH&S issues.

Kumar Choudhry
1 year ago
Kumar Choudhry 1 year ago

Wonderful suggestions and advice here! Thanks to you all for your invaluable contributions. I now know what might and what is happening once we discharge the waste acid into the leach tanks. Especially the head tanks’ will also do a bottle roll test with the waste acid in one and the normal CIL condition also. After the test i will let you know the impacts on the leach kinetics.

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