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Manual Agitation of Vat Leach (6 replies and 2 comments)
I believe that it is better to pump the vat from the bottom and recover the pregnant solution from the top. The potential problem is the turbidity, it could have an impact on the efficiency of the recovery process ( activated carbon, zinc powder).
Your comments don't mention the gold grade. Probbaly, it is important to evaluate the project profit.
Yeah I thought it would be better to pump from bottom up.
The recovery was going to be through activated carbon, perhaps I could pump it into a settling pond and or add some flocculant , or a through a filter.
Grade is around 1.5 to 2.5g/t , the testwork got 68% recovery from just agitating it in a steel reactor so if i could get similar recoveries I'd be happy.
Activated carbon is an option to recover gold from solution by contacting the solution with granular activated Carbon-in-Columns (CIC Process). You will have to take a decision about the carbon, I mean install a small plant to treat the loaded carbon, sell the carbon or contact a contractor to get the dore bar.
The loaded carbon should be no issue as there are established contractors in the region that will strip the carbon into dore for a fee.
I've spoken with a consultant and I was going to get some testwork done to get a size analysis of the gold distribution, it might be possible to just screen the fines out to get an acceptable recovery and stockpile the fines for processing later.
I still might need some work on the process water going into the carbon columns, from what I've read turbid clay water can block the pores in the carbon very quickly, I was looking at either hydrocyclone ( seem tricky to set up ), fine mesh dewatering screen or lamella clarifier which seems appealing because there are skid mounted units available which you can rent.
Also from talking with him it seems like agglomeration might just be unavoidable, and would save a lot of headaches and the project potentially failing catastrophically.
Vat leaching is much more complicated than a heap. By the time you finish farting around with solutions, turbidity. liners, mixing etc... you should do one of two things build a heap or install a proper agitated leach. You are setting yourself up for a pile of headaches and perhaps some environmental liabilities as well. The word gently and excavator dont belong in the same sentence. Ever considered building a crib to do the heap leaching in?
Kind Regards
Todd Harvey - Global Resource Engineering http://www.global-resource-eng.com
Agreed, the excavator idea is one pierced liner away from a disaster.
The reason I'm aiming for the vat leach rather than heap is just because the study and previous owners plans seemed to lean towards the vat. I thought this might be because the ore has a high fines, high clay content and percolation issues perhaps vat leaching might help with it being fully submerged in the solution which is sorta like a low height heap lift with a very high irrigation rate.
In the other thread, you mentioned its possible to agglomerate directly off the belt stacker which seems like a pretty cost effective easy idea i might look into further.
Vat leach is really only good for high grade, low throughput - 1 man and a dog type operation.
For the grade and clay you have you should just go for standard agitated leach and activated carbon system as you need high gold recovery to make money.
Cheers
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I've posted here before about a project I've got that has problems with high clay content requiring large cement addition for percolation. Part of the testwork looked at simply crushing it and agitating in a vessel and it got decent recovery.
I was looking at doing this because even though you sacrifice recovery it's a lot simpler then running it through an aglomeration plant. I was wondering if manual agitating/mixing the vat would help with recovery and prevent the clay slime from blinding the ore and did anyone have any ideas on ways to do it?
My only idea so far is to sit there and very carefully turn it over with a long extension arm excavator.
Also does anyone know if its better to pump the vat from bottom up then siphon the pregant solution off the top or pump top down and suck the preg solution from a drain coil at the bottom?