I understand that you have lost gold in the process and, as a result of this, the calculated head law does not coincide with the law of entry to Plant ... I suggest you take into account the following:

- The mineral must contain a bit of coarse gold above 300 microns ... The coarse gold is accumulated in the classification grinding circuit and every so often it is thrown from the system towards the cyanidation stage and, due to its high specific gravity , it falls to the bottom of the tanks ... You must remember that, the thicker and bigger the gold particle, the longer leaching time is required.

- I do not know if you have done a sampling and balance of gravimetric gold in the grinding and classification ... It is very likely that you have accumulation of free gold in the U / F of the hydrocyclones ... I suggest you perform the sampling and balance of the circuit.

- Currently, you are using centrifugal concentrators in the grinding-classification system ??? ...

- In the cyanidation tanks are you leaching sulfide flotation concentrate or mineral head? ...

I look forward to your confirmation.

Sincerely,

Ismael Molina

thanks for the reply ismael. i also thought this could happen. we got centrifugal concentrator, but its not working any more. only hydrocyclone. we don’t do gravimetric sampling in mill, but we did change the liners every six months, where we clean and take the fine dust from the liners to smelting, but the end result is not that much as expected. the ore is not sulphide but oxidized and nuggets of gold. 

Hi.
In the presence of gravity gold, the problem can also be in sampling and analysis of feed. Gravity gold can increase the feed. You need to change the sample preparation.

Hi - can you explain your circuit a little more? Are you talking about underflow from the gravity circuit or the concentrate? Anything coming out of a gravity concentrator would be too large for CIL so should go to regrind (underflow) or to finishing table or similar for concentrate.

I suggest you remove the inspection covers on the base of the leach tanks next time you reline the mill and sample the residue.  Given that the slurry is in constant cyanide the gold build up is generally small (compared to gold behind the mill liners), but if oxygen levels in leach are low there maybe some residue.  Errors in sampling are normally the main culprit for lost gold, especially heavy particles that are not adequately sampled by the tailings sampler, which is often not deep enough,  though gold on CIP carbon fines can also be a factor (fines being carbon that escapes through the capture screes). I have run several custom milling stock-takes and residual gold in tanks generally does not cover my fees.

Wise Technology and the Particle Settling Rate Sorting Process would concentrate gold from any coarse size through fine crushing and grinding to the practical limit of the porous support. Where gangue silicates would have a limit of say 40 microns in bed formation, gold could be treated much finer to the Newton/Stokes laws equivalents. But the limit is the porosity of the porous support medium. The gold concentrate would be very high-grade diluted by composites.