Pyrometallurgy: Roasting, Smelting, Refining & Electrowinning

Pyrometallurgy: Roasting, Smelting, Refining & Electrowinning2017-04-21T02:33:06-04:00
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Activated Carbon (4 replies)

oro
1 year ago
oro 1 year ago

For batch leach samples - instead of stripping the AC I was wondering if it can be smelted, maybe with a bit of litharge as a collector and some borax to slag off contaminants.  I understand the carbon can be “ashed” in an electric muffle furnace (I don’t have one) but assume a gas furnace or torch would create too much wind and either volatilize the microscopic gold particles and/or blow the particles and ash out of the vessel - hence the smelting question.  I’m talking about less than a handful of AC.  

rob riggir
1 year ago
rob riggir 1 year ago

Hi Oro,

I am working on exactly this concept for a small vat leach gold operation. The AC can be ashed and then smelted to recover the gold as bullion. There are a few tricks which need to be considered to make it all work though.

oro
1 year ago
oro 1 year ago

Yes, smelt the ashed carbon but what about direct smelting the carbon and skip the ash step which is 6-8 hours in a muffle furnace at 650 C ?  

Please share the tricks you mention, thank you!

 

rob riggir
1 year ago
rob riggir 1 year ago

Hi Oro,

Generally, a 2 stage step is done to reduce the volumes for smelting. You only have a small amount of AC therefore you can do both stages at once. A couple of things to look out for though;

  • make sure that the AC you are using will ash easily. Coal AC, being softer, will ash faster than coconut shell AC.
  • do the ashing/smelting in a crucible inside a furnace. Do not use a gas torch applied directly to the AC as you need the ash to settle in the crucible and not blow away as fly ash. To be sure, you should use a bag filter on the furnace exhaust to recover any fly ash.
  • keep the crucible temperature low (400-600C) until the ash has formed. This will take several hours. 
  • remove the ash and mix fluxes. Pour mixture back in to the crucible and heat to 1200C, slowly raising the temperature.
  • gold will form a button in the bottom of the crucible.

Good luck!

oro
1 year ago
oro 1 year ago

Rob,

So...ash / smelt in the same vessel and furnace, an elegant solution.  thank you!

 

 

 

 

 

 

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