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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CIL Carbon Concentration (5 replies)

1 year ago
Sudhirkumar 1 year ago

Normally what is the optimum carbon concentration at the gold CIL process? I need some advice to maintain 7 CIL tanks.Currently we have 3 leach tanks in the front and then followed by 7 stages of CIL.

Dizzy Flores
1 year ago
Dizzy Flores 1 year ago

10 g/L as a stab in the dark because we need more information to give you the optimum number! See, the more carbon you have, the better the adsorption of Au onto the carbon initially. But you can only strip off as much gold as you put in once the CIL is in steady state. This may mean the residence time of the carbon gets up to 3 to 4 weeks. By then the carbon can become scaled and the activity very low. So you want the minimum amount of carbon you need to keep the tail solution at 0.02 g/L or less.

Also a CIL generally cannot achieve the same loading as a CIP circuit. The Au loading is related to the solution grade in the first ads portion tank. With CIP, the solution grade is generally pretty high, as the gold is leached first. With CIL, leaching and adsorption start at the same time in the first tank; hence the solution grade doesn't get really high.

If there is no reason to have a CIL, like preg robbing etc, you can achieve higher loading by using the first tank as a leach tank, followed by 6 stages of CIL.

1 year ago
OberstGruppen 1 year ago

You should run a simple carbon load optimization tests using your ore and your carbon. I could share you some past experience but may not applicable for every ore.

John Koenig
1 year ago
John Koenig 1 year ago

He has described the fundamentals very well, you can also run a varying carbon concentration across your circuit to maximize recovery while minimizing carbon inventory. For example, run 15 g/l in the first two tanks, drop to 5 or thereabouts for the next three, and then increase again for the final two to mop up any gold in solution. This might be especially valuable for you with the preceding leach - your tenor entering the first CIL tank will be high, so while the equilibrium may then encourage high loadings, you might need to consider higher carbon concentrations here to maximize recovery.

Carmen Ibanz
1 year ago
Carmen Ibanz 1 year ago

I recall similar topic discussed here recently.
Generally concentration of carbon (adsorbent) in pulp (PLS) is defined by mass balance. On one side of equation you have gold containing flow (pulp flow) multiplied by known gold concentration. On another side you have carbon flow multiplied by its gold capacity. Divide carbon flow by pulp flow and you will have concentration of carbon in pulp. Do not forget to apply appropriate engineering parameter (X1.1) for the sake of security. The carbon gold capacity can be obtained from small scale lab experiment. Remember that carbon is to be loaded with gold at equilibrium gold concentration in the feed equal to its initial concentration. It implies that you are to use large excess of the feed (like 5,000 to 1) either change the contact feed with portions of fresh one while the carbon can still load more.

Philip Stewart
9 months ago
Philip Stewart 9 months ago
2 likes by ThabisoKwenane and David

The amount of carbon in a tank and hence its concentration are important to ensure that the amount carbon and its residence time are sufficient to ensure that the solution concentration and the loading of the carbon come quickly into equilibrium.  The mass balance is determined by the rate of counter-current movement of the carbon and its final loading which must equate to the rate at which gold (or silver) is leached so that as little as possible is left in solution.  Mean carbon residence times of the order of four days in a circuit are typical and are compatible with concentrations of about 10 g/l.  If the amount of carbon is very high then it will spend an unnecessarily long time in circuit and be subject to undue fouling and damage by attrition.

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