Help with Ore Processing

[Deano]

If you are going to leach the tailings from a gravity process then what method you use to remove this coarse gold from the ore stream before the leach step is dependent on the size of the gold particles and the level of these particles in the feed.

You have three scenarios.

Firstly there is no coarse gold in which case all of the feed is leached with no gravity circuit.

Secondly there is only very coarse and very fine gold in which case you would be able to remove all of the coarse gold with a simple sluice prior to leaching the sluice tailings.

Thirdly there is coarse, medium and fine gold present in the ore. The coarse gold is removed by a sluice, the fine gold will be leached, the medium gold is that which may require a third processing step. When I say medium gold I am talking about 75 to 300 micron sized particles, these are the ones which are getting too large to leach but which are also getting too small to recover in a sluice.

The first thing to establish is how much gold is present in the medium size range, if there is a substantial amount then it may be worthwhile to put in a circuit to recover it.

If there is not a lot of medium gold then you let it go to the leach system and accept that there will be some smallish losses from incomplete leaching, you have to be pragmatic about this.

If you have a lot of medium sized gold then you have two options depending on what volume of material per hour you are treating.

For smallish operations, say 1 to 10 tons per hour, you would usually use a jig to extract the medium gold.

For larger operations you would use a Gemini table.

There are many centrifugal concentrators on the market which do a good job but they also do a good job of emptying your wallet. Not recommended for small operations.

The cons from a jig or Gemini table will need to be either leached in a dedicated circuit or cleaned up on a Wilfley table, the table tails are sent to the leach circuit.

Deano

 

[cuchugold]

If you are going to leach the tailings from a gravity process then what method you use to remove this coarse gold from the ore stream before the leach step is dependent on the size of the gold particles and the level of these particles in the feed.

You have three scenarios.

Firstly there is no coarse gold in which case all of the feed is leached with no gravity circuit.

Secondly there is only very coarse and very fine gold in which case you would be able to remove all of the coarse gold with a simple sluice prior to leaching the sluice tailings.

Thirdly there is coarse, medium and fine gold present in the ore. The coarse gold is removed by a sluice, the fine gold will be leached, the medium gold is that which may require a third processing step. When I say medium gold I am talking about 75 to 300 micron sized particles, these are the ones which are getting too large to leach but which are also getting too small to recover in a sluice.

The first thing to establish is how much gold is present in the medium size range, if there is a substantial amount then it may be worthwhile to put in a circuit to recover it.

If there is not a lot of medium gold then you let it go to the leach system and accept that there will be some smallish losses from incomplete leaching, you have to be pragmatic about this.

If you have a lot of medium sized gold then you have two options depending on what volume of material per hour you are treating.

For smallish operations, say 1 to 10 tons per hour, you would usually use a jig to extract the medium gold.

For larger operations you would use a Gemini table.

There are many centrifugal concentrators on the market which do a good job but they also do a good job of emptying your wallet. Not recommended for small operations.

The cons from a jig or Gemini table will need to be either leached in a dedicated circuit or cleaned up on a Wilfley table, the table tails are sent to the leach circuit.

Deano

Thanks a lot Deano. The samples I have are not very consistent, sometimes there are plenty of nuggets, sometimes only finer dust. I never even considered the 'medium size'. I have to look in more detail. Thank you for that too. Would a jig recover the coarse and medium together, before any leaching is necessary?. What jig would you recommend for a 1 ton per hour operation?.

edit to add: Another question for Deano: Is this a good plan: Feed the placer ore, as is, into a jig, then sieve the tailings at 200 mesh (75 microns), discard the coarser, and accumulate the finer into a pit for future leaching. The concentrates from the jig also sieved and fed to a table for cleanup. Tailings from table to leaching pit (or dedicated strong leach small tank?). Alternatively, I could put a sieve stack (vibrating along with the jig motion), on top of the jig, to catch coarser nuggets, etc. With different size iron shot in the 2 or 3 sieve stacks, some sorting and milling will happen at the same time. Simpler that way, perhaps.

 

[Deano]

The reason you run a sluice in the feed line of a jig is to not have to keep sorting through all the jig ragging looking for any nuggets.

Generally a jig will handle about 1 ton per hour of ore for each square foot of jig area. If your gold is trending to the minus 100 micron size then the jig feed rate is dropped to around 1/2 ton per hour or less.

The jig tails are panned to see what feed rate is appropriate for your gold size. If you see fine gold in the pan you slow down the feed rate.

The feed to the jig must be screened, usually a 3mm screen is used.

The coarser the screen used the greater the losses of fine gold on the jig.

Screening the jig tails at 75 microns sounds simple, in practice it will involve a large amount of hand sieving.

My preference would be to carry out some leaching tests on say the 1 to 3 mm fraction of the jig tails and see if there are enough values to be worth leaching, similarly for the minus 1mm jig tails.

The results of these tests will tell you whether the entire jig tail should be leached or just the minus 1mm fraction or maybe none of the jig tail.

You are trying to get a smooth feed entry on to the jig, the last thing you want is to have some further equipment making this difficult to do. Any milling done will be minimal and not worth the expense of doing.

All jig cons are cleaned up on a table ready for smelting, the table tails usually report to the leach circuit.

Deano

 

[cuchugold]

Deano: It all makes sense. I truly appreciate your counsel. Now it is time to get to work, stop thinking, kill all the engineers, and start shoveling dirt for me.

I'll report next year what happened, or sooner if I get any questions. I see a plan coming together, even leaving a Vat leaching on-site while I'm away. At 5 meters depth (~bedrock), there is no shortage of water at all.

If you could suggest a model or type of jig to use, that perhaps I could manufacture, that'll be a bonus.

Cheers.

 

[Platdigger]

I hope you guys don't mind my putting this here, and I know it probably won't help a guy much clean over in Ireland, but, I just happen to have such a jig as is being talked about in this thread.
I believe it is good for about ten ton per hour. I was not able to use it were I wanted to. So there it sits.
Again, I hope this is not an interruption to this thread. Good thread by the way.
As all the threads are were we are so lucky as to have Deano post in.
The gold I intended to use it on is pretty small, probably 80 to 100 mesh. May not have been the right piece of equipment for the job anyway.
And only a few grams per ton.

 

[cuchugold]

Only my ancestors and one passport are from Ireland. Never been there!. Good luck selling the equipment. Adieu.

 

[cuchugold]

I hope you guys don't mind my putting this here, and I know it probably won't help a guy much clean over in Ireland, but, I just happen to have such a jig as is being talked about in this thread.
I believe it is good for about ten ton per hour. I was not able to use it were I wanted to. So there it sits.
Again, I hope this is not an interruption to this thread. Good thread by the way.
As all the threads are were we are so lucky as to have Deano post in.
The gold I intended to use it on is pretty small, probably 80 to 100 mesh. May not have been the right piece of equipment for the job anyway.
And only a few grams per ton.

Can you post some photos of the jig?. Electric or gas?. Dual or single?. It must be very big for 10 T/hr. What's the weight?. Where is the equipment located and the asking price?. I think it's too big for my purposes.

 

[Platdigger]

Well first off it is in Wa State. Just went up there to get some pics and the phone went dead.
It is dual.
It is electric. Looks like probably a 5 horse. My plan was to switch it to gas.
It must weigh around 1000 to 1200#. Just a guess.
I have the measurements of the screens some were.
Could all ways go back in the next few days and get any dimensions you might want.
Asking price? Make me an offer, I just might take it.
By the way, this thing take a lot of water to run it. Not sure how big of a pump it would take.

 

[cuchugold]

Thanks Plat. It's too big for me.