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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Small Scale Batch/Pilot CIL Plant, Slurry Adsorption (2 replies)

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redcastle
5 years ago
redcastle 5 years ago

I have a small ball mill ( 1 to 2 tph ) and plenty of oxide ore and I was looking at the feasibility of building a test small scale leaching circuit that could be run in a batch style to keep it as simple as possible.

My current idea is once the ore is milled to an appropriate size, it is mixed with water to chosen density and pumped into a couple of old agitated tanks I've sourced.

I thought then add lime to the tanks to get the pH up to around 10, then slowly mix/add by hand ( with a respirator ) the cyanide solution. Once it's all mixed the agitators are run, cyanide/pH levels monitored for 6 to 10 hours. For oxygen is it possible to use a simple bubbler setup or easier to just add a chemical agent?

Once it's leached I'm not sure of the easiest way to handle the pregnant slurry, I know in proper setup you'd have the carbon flowing in a counter current manner but I'm looking for a simpler way, I thought maybe just letting the tanks settle, maybe add a bit of flocculent then slowly decanting the water off the top and circulating it through some carbon columns I've also sourced, or my other idea is maybe it would be easier to just add the carbon in the tanks during the leaching process then just pump the slurry through a proper carbon screen. Once it's all collected then it can be washed and transported to a contractor for stripping.

For the tailings I was going to pump them into a lined pond then try and decant some water to reuse and then destroy the cyanide with either peroxide or hypochlorite, from what I gather hypochlorite is the cheapest/most powerful oxidant but will this still be too dangerous even if I up the pH of the tailings and use a full respirator when adding the hypochlorite?

Also I want to try and reuse water so I'm guessing I'll have to try and lower the chlorine level ( or just let it naturally degrade? ) before I reintroduce it to the circuit, also would there be issues flocculent levels recirculating?

My other idea is building a plant is perhaps too hard and I should sell the ball mill and buy agglomeration equipment and look at heap leaching it instead, but they sound almost too deceptively simple plus losing 40 to 50% recovery, has anyone had a good experience setting up a small pilot heap? The ore is pretty varied theres plenty of low grade ( 0.6 - to 0.8 g/t ) and and small sections of high grade ( 5 - 10g/t)

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Todd H
5 years ago
Todd H 5 years ago
Like

Your concepts are fairly good but it is never as easy as one would think.

You can do batch leaching - but I would suggest you want closer to 24 hours of retention time. Any device that can add air to the tanks will work but keep in mind it has to have enough pressure to overcome the pressure of the slurry head.  Small air compressors work fine but they are costly to run and are not typically meant for continuous duty.  Blowers are more common - roots type - and there are also some reasonably high-pressure blowers available for pond aeration that can work in this application.

You can mix your own cyanide or buy it in a liquid form.  Keep the pH high and wear a respirator when handling powder. I would get a small chemical pump to add it to the tanks.  You will also need a pH meter and some titration equipment for cyanide control.

Decanting the tanks will work but you will need to refill, and re-agitate a coiuple of times to make sure you dont leave 50% of your gold solution behind. A better idea would be to filter the slurry and wash the solids, create a clean preg solution and clean tailings.  The tailings can be repulped so you can pump them to your pond.

I would recommend that you use a Merril Crowe circuit for your gold recovery, there are small units available and 911 Met can supply them. You will need a refining process for the precipitate and 911 Met sells those as well.

As for cyanide destruction, peroxide is your best bet as it does not have any residual chemicals to worry about i.e. chloride.

Hope this helps.

 

Regards

 

 

Todd Harvey - Global Resource Engineering http://www.global-resource-eng.com

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redcastle
5 years ago
redcastle 5 years ago
Like

Hi Todd thanks for the reply, I didn't think of filtering the slurry and that seems like a good idea, washing the tailings will probably help with enviromental approval as well.

I don't know much about filtration would a filter press be suitable or just add double handling, my uncle has a fabrication workshop and has offered to help so I thought maybe making some tanks with a filter cloth/plate and a vaccum setup might be easier to run water through for the wash then just repulp and agitate to pump into pond.

I didn't realise they made small Merril Crowe setups and they look quite compact and simple so I'll look into that as well, cheers.


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