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Flow rate in VAT leaching (3 replies and 1 comment)

Dan88
1 week ago
Dan88 1 week ago

Good day,

I am trying to figure out the optimal flow rate for a large tank. I am used to 30 ton VAT tanks but have since started using a 150 ton VAT tank.

I know that with a 30 ton tank the flow rate is around 5 l/min but if i use the same flow rate in a bigger tank it takes forever to load the carbon.  Is there a ratio i can use or some equation to find the optimal flow rate? 

Also i am new to the whole cyanide percentage in solution as previously i have used potassium iodine to check the cyanide concentration in the solution. What is an acceptable range for the cyanide strength? I have been told between 0.18 to 0.2% but on investigation on the internet i have read of 0.02 to 0.05%

I would be greatful to any help i can get. Thanks in advance 

Rheomet
1 week ago
Rheomet 1 week ago
2 likes by Cyanide and David

On the flowrate, I am not aware of a specific rule. I used to go by residence time per cycle, bearing in mind that a laminar regime  is generally sufficient. You need to know the void volume at start and finish for an accurate estimate, some base line kinetics data would also be highly useful.  Sodium cyanide at 0.5 - 1 g/L NaCN is generally standard for gold cyanidation, I would try the lower range unless you have copious amount of silver. Make sure you keep the pH at 10.5 - 11 preferably with lime, can use sodium hydroxide if the reaction is too slow or/and the residue is too sticky.  If you have PGMs or refractory gold in your feed, you may need intensive cyanidation which is an entirely different ball game (15 g/L NaCN, heated tank).

Hope this helps. Cheers, Alex.

Dan88
1 week ago

Thanks Alex that dose help indeed.

Cyanide
1 week ago
Cyanide 1 week ago

Thank you Alex. Dan, you should look at http://www.ausimm.com.au/sections/Gallery/webinar_flyer_cil_cip_plants.pdf and contact them to get the script. Also see https://www.911metallurgist.com/blog/cil-cip-leach-circuit-simulation by Philip Stewart.

kahonde
2 days ago
kahonde 2 days ago

0.1% is the ideal but if you leaching high grade ores you might need to use 0.18-0.2%

 

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