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Recovery on cil plant (3 replies and 2 comments)
A couple of questions to get the scope correct:
- Are you looking to investigate a plant that is in production or a potential plant design?
- Sampling is critical - your results will only be as good as your samples.
Thoughts:
- If the plant is already running the best way to define the recovery is to utilize composite samples of the feed and tailings. Obviously gold recovered is the ultimate answer but people play games with head grade adjustments to make recovery better.
- If you are looking to test plant conditions a bottle roll is a good test. It can simulate plant conditions well if you know what you are doing - grind size, CN concentration, oxygen, carbon content, time.
- Areas that differ between a bottle roll and a plant stirred tank - oxygen concentration, CN concentration (is it added stagewise or all up front...) carbon activity - bottle rolls typical utilize fresh carbon while plants do not - solution losses can be widely different. Also is there gravity recovery prior to leaching - coarse gold can impact leach results. Sample size - bottle rolls are a small sample and should be repeated on every ore type, and at least conducted in duplicate.
Hope this helps. Contact me if you need further assistance.
Todd H
Todd Harvey - Global Resource Engineering http://www.global-resource-eng.com
Thanks for the reply Todd it is an existing plant that we are treating our material at, composite samples are being taken and a few bottle roll tests is taken on batches of 2000 tonnes, the guys now indicate to us that they test the material on plant conditions with carbon and then with no carbon and want to use a recovery somewhere in the middle, this does not make sense to me. There is no gravity circuit and the material is tested at plant conditions and results are always over 85%.
To me testing without carbon is not a simulation of the plant?
You are absolutely correct to challenge "the guys" method of giving a recovery somewhere in between. That has no basis, other than to under-rate your recovery in their favor. And the previous commenter had it correct that your sample is of first critical importance, and all the specific conditions within the bottle roll are also to be controlled, studied and made to resemble the process plant (full scale). That being said, if your processor is running your material through at a sub-design scale rate, there may be additional influences on the recovery. Appropriately scaled lab testing, up to and including locked-cycle work may be warranted.
Comments above endorsed!
Also, I often find the biggest difference between plant and lab arises due to a difference in grind size. It is very difficult to reproduce a plant grind in the lab. You may be able to match the P80 but the plant almost always has a much flatter size distribution than a lab grind and this can impact recovery quite substantially. Generally there is a better correlation if you match P95's for leaching. Flotation is quite different and a P80 may be more appropriate in this instance.
Hi John. May be my question is a litle bit out of the context of this discussion, but we are facing a dilema, regarding P80 x recovery: there is an information that some tests showed a CIL recovery decreasing (yes, decreasing) above P70. Do you know any similar case ? Is it possible ?
Just need some confirmation on whether the correct and most accurate manner of testing recovery of material placed into a cil plant let’s say 30000tonnes of ore out of a plant with capacity of 150 000 tones of ore is indeed to do a bottle roll test on the plant conditions with carbon. Note different sources of material is fed into same plant.
thanks in advance for your inputs