Gravity Separation & Concentration Methods

Gravity Separation & Concentration Methods

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How to Separate Gold and Black Sands (3 replies)

2 years ago
David 2 years ago

We installed our iCon i150  some time back but something isn’t ok as there is no separation of gold and black sands despite following all the procedures. I wonder if there is perhaps a problem with
the electric engine RPM not being high enough....Any thoughts....

Half the black sand falls thru the proper outlet, the other half goes where there should be only gold......

PS: this question can via email. I am posting it for everyone to use.

2 years ago
David 2 years ago

I discussed your question with one of my process colleagues in order to get his input on separation of gold from black sands. It can be difficult to get a good separation as the black sands are quite dense. This is even more apparent when dealing with coarse sand and fine gold. I believe the i150 will be setup to run at a maximum speed of 50Hz. The speed can be increased if necessary but keep in mind that additional g-forces will then be imparted against all of the material which may or may not be beneficial to separating the gold from the black sands. The speed may also increase the wear rates to parts of your machine which may need to be considered versus a potential net gain in expected recovery. I’m sure that you are also aware the majority of your concentrate will still be black sands with the gold contained within it and will need further upgrading.

Our suggestions for the interim:

  • Increase the fluidization pressure/flow. Our default recommendation is 15 psi but running upwards of 20 psi should be trialed here.
  • Feed the machine gently and evenly. Try to ensure that there is no surging or large changes to the feed flow rate.

Let me know if you have any questions.

2 years ago
SmartDog 2 years ago
1 like by David

A couple of ket items, if this is really fine gold, check the gold shape.  If they are flat flakes they will behave as if they are significantly lower in specific gravity.  This means that they will float when you expect them to settle.  This means that you may need to do a two step process with the second stage at much higher rpm.

Alternatively try flotation.

Gene Cheeseman
2 years ago
Gene Cheeseman 2 years ago

From my experience high upgrade ratios will be difficult as the black sand tends to saturate the bowl quite quickly.  The high fluidizing flow reccomendation is correct as it will keep the riffles dilated and able to recover gold longer.  

Generally, running shorter cycles to increase the mass yield and putting more than one machine in series will help to improve "rougher recovery".

Similar to SmartDog's comment - cleaning these concentrates on a shaking table will be difficult.  Small batch flotation cells have been shown to be very effective at selectively floating this free gold from black sand concentrates.

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