Hydrometallurgy: Leaching in Heap, Vat, CIL, CIP, Merrill–Crowe, SX Solvent Extraction

Hydrometallurgy: Leaching in Heap, Vat, CIL, CIP, Merrill–Crowe, SX Solvent Extraction

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CIP/CIL cyanide leach aeration - air/oxygen flow rate calculation (1 reply)

P
pz
4 weeks ago
pz 4 weeks ago

Hi everyone. I wonder how is oxidizing gas (O2/air) flow rate is calculated for the atmospheric cyanide leach.

I have experience with pressure oxidation of sulfides. The calculation method is very straightforward. First – calculate stoichiometric consumption for reactions. Second – consider for the O2 utilization (usually 80-90%) and distribute gas in accordance with kinetics in compartments.

With cyanide leach, however, it is different. Stoichiometric consumption is extremely low (Elsner equation). As well as O2 utilization. But we know that we must blow enough air/oxygen to provide high dissolved oxygen content (8-10 ppm? sometimes higher with special aeration devices). Is that the main design criterion?

If so, how to calculate what is the air flow rate to provide that DO content?

And what is the standard industrial practice: how much air is fed to the CIP/CIL tanks? In Nm3 per ton of solid or Nm3 per 1000m3 of slurry… Any indication will help.

Thanks.

J
Jorge
3 weeks ago
Jorge 3 weeks ago

If you know the slurry flowrate, you can determine the DO transported in the slurry. Usually, cyanidation is performed at a pH higher than 10.5 and DO higher than 6 ppm. Essentially, the rate of gold dissolution will increase if the DO is higher than 10 ppm.

Air is the source of oxygen and is normally supplied in two forms: the first one is a low-pressure air for aeration in the leaching circuit. The key point to consider is the static head required for aeration as this will indicate the type of blower. The second form is a high-pressure compressed air for instruments and airlifts.  A Compressor is supplied with their own control. The oxygen mass-transfer rate is influenced by the slurry density.


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