Gravity Separation & Concentration Methods

Gravity Separation & Concentration Methods2017-04-04T06:57:23-04:00
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Integration of Knelson or Falcon gold concentrator to CIL process (8 replies)

1 year ago
Pingarroncesar17 1 year ago

I currently run a Toll mill “CIL” operation in Perú. We have a 150Ton/D mill. We process Gold ore oxides and sulphides. The ore we process may contain around 20-45% corse gold depending on the grade. The head grade of the mill is 9gr/Ton.

we have run metallurgical test using Falcon concentrator on different blends and the results have been successful having recoveries up to 65% ( Coarse+Fines )

Our problems comes when trying to recover the gold left in the slurry as the concentrator uses too much Water as the density goes to high to send the slurry from the concentrator to the CIL ranks.

We are thinking about thickener tanks before CIL circuit.

I appreciate in advanced the comments on what can be the best setup to integrate the Falcon or Knelson concetrator into our CIL process.


Gene Cheeseman
1 year ago
Gene Cheeseman 1 year ago

Hi Ping,

Did you do your testing with a lab Falcon or a pilot trial with an industrial machine.

Laboratory concentrators use much more water per kg of material treated than an industrial machine.

A thickener before the leach circuit is not uncommon but may not be necessary. A few points to consider:

-Knelsons typically use more water than the same size Falcon

-Selecting the right size concentrator will minimize water usage; having an oversized machine will cause more slurry dilution

-If 65% of your gold is reporting to your gravity concentrate, having a lower density and thus a lower retention time in your CIL circuit might not be as critical as you only have 1/3 of the gold to leach


1 year ago
Katov 1 year ago

Hi Ping,

As suggested by Gene, all Falcon gravity circuit be the way to go. If your gold is mainly present as fine to ultra fine, consider the Ultra Fine Falcon machine.

If you redirect your gravity tails and associated water back into your milling circuit water balance, you should still be able to maintain your leach feed density.

You may also consider gravity on your leach tails as opposed to in the milling circuit and recover any un-leached gold there..but has risks.


1 year ago
Pingarroncesar17 1 year ago

Good Morning guys. First of all thanks for the inputs.

  • The testing was made in the lab with a Falcon ( Icon ) model.
  • We are looking to integrate this equipment:  The situation here is that as we have 150Ton/D mill process this will be around 6.25Ton/H. We have to maintain this capacity to be able to reach 88% - 90% - 200mesh in our grinding process and the 2 falcon units available are I150 (2ton/H)  - I 350 (10ton/H).
  • The problem with the dilution comes when adding the activated carbon to the CIL tanks ( they will go straight to the bottom) . One way around we are looking is to increase the oxygen flow we put in the tanks. But over saturation might take place.

The second situation I need to solve: Where to place the unit? The mill setup is like this. 

  • Right after our primary mill or at the over the ht main Hidrcyclone?


1 year ago
Pingarroncesar17 1 year ago

Here are some attachments that will illustrate the whole situation.

Again thanks for taking the time to help me out.


1 year ago
Pingarroncesar17 1 year ago

Flowsheet of the mill.

1 year ago
Jorge 1 year ago

If the sample that you tested came from dry grinding (molino polveador), you should repeat the test using a sample obtained from wet grinding. The production of gold flakes is different, and probably, the recovery by gravity too. If the results are  similar, it is necessary clean the concentrate using a shaking table to improve the gold grade. Here, you have to think what to do with the middlings because they should content gold. 

The feed to the centrifugal concentrator should be a fraction (e.g. 15% to 25%) of the ball mill discharge or hydrocyclone underflow. In this way, you can control the slurry density in the grinding circuit and CIL circuit.

Gene Cheeseman
1 year ago
Gene Cheeseman 1 year ago

As Jorge said the best location for the concentrator would be on cyclone underflow or ball mill discharge/cyclone feed.  I would recommend the i350 (or SB400 same machine but with automation - not manual operation). 

From my experience these machines are comfortable up to 15 t/h and will add about 3-4m3/hr of water to your circuit.

In this case I would probably recommend installing on the cyclone underflow and have the tailings report back to the mill feed. If you scale back your mill water addition you should not have any problems upsetting your grinding and CIL densities.

Liberated gold will preferentially report to cyclone underflow, even at sizes much finer that your COF P80. By installing the concentrator within the recirculating load of the grinding circuit you give the machine multiple chances to recover the gold as it is liberated.

rob riggir
1 year ago
rob riggir 1 year ago

Hi Ping - if your activated carbon sinks in your leach tanks then you have a major slurry low density issue or your agitators are not working well. Adding a Falcon, of course, will add water so will add to your issue. Sounds to me like you are milling at a very low density and this is being carried through to your leach tanks. A pre leach thickener is an expensive option - check your milling density first. Contact me if wish. Good luck.

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