Fine C from the strip circuit & slag from the refinery are generally drummed & shipped for metals recovery, usually by pyro-metallurgical techniques.

I have not heard of a commercial process for mine-site recovery of metals from fine C; over a decade ago, Fort Knox mine (Alaska) was investigating gold transfer from carbon fines to virgin carbon; encapsulation of metals in slag render hydro-met techniques redundant even at grind sizes <35-micron.

I think the transfer method is not bad. Only it must be more.

The tests at Fort Knox mine used fine carbon containing up to 20oz/t (0.68 kg/t) and transferred 95% of the gold to fresh (Virgin) carbon using a cyanide solution above 0.1%.

You may also want to read the paper by Rowe & McKnight http://is.gd/QC8Zy9 however several refineries will process these fines for you and that may be cheaper if you do not wish to keep the carbon.

So it is strictly pyro-metallurgical method that can be used to refine fine carbons. The transfer method sounds interesting. Will try with a test work and see its viability.

What quantity of carbon per week or month will be treated?

We are looking at 500 to 800 tonnes per week for the initial stage and see the economic viability and also the test may require floating the carbons. I guess a heavy media separator may be required. Any media i can refer to? Must be cheap and available though!

Is your numbers correct 500-800tonnes/week, as this is extremely high if you are referring to activated carbon in your circuit which you are "losing" if this is the case you have a bigger problem in the circuit?

No this is not what we are losing. I am looking at a design of a process to refine them. Its forecast figure or target. Also we will acquire them from different mines as well. I heard there are a lot in the system, as in different mines around. At the moment we are thinking about a hydrometallurgical way of refining them i.e. the fines other than the pyro-metallurgical means in existence.

The budget numbers you quote for fine carbon losses (if that is what you are referring to) are enormous. The conventional recovery method for gold from fine carbon is via ashing of the carbon and then further hydrometallurgical treatment of the ash. There is a company here in SA who supplies this technology and I understand they have at least one commercial operation in West Africa.

So maybe i might have forecast an overly figure. But I really want to know more about the ashing you are talking about. It will be interesting.

Not having knowledge of your process it is difficult to assess the source of the fines. Agree with harry that the tonnage you refer to may be incorrect, suggest you check this. From our benchmarking the losses of carbon that are estimated from the makeup of new carbon is between 20g/t and 80g/t of ore processed through CIL or CIP circuits. Fine carbon recovery in the elution and carbon re-activation system is crucial as any fine carbon which is smaller than the absorption circuit screens will absorb gold and be lost to residue with the value of the gold being much higher than the carbon itself. It therefore makes sense to remove as much of the fine carbon as possible but also establish the reasons for the fine carbon generation. This can usually be managed.