Gravity Separation & Concentration Methods

Gravity Separation & Concentration Methods2017-04-04T06:57:23-04:00
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best method to liquefy extreme clay ore (6 replies)

2 years ago
oro 2 years ago

milled ore tailings are sometimes clay bound (slime) to an extreme and even a standard scrubber trommel will not achieve a complete wash and the small and large clay balls become problematic downstream. It's very much like caliche clay.  What methods are there to liquefy this sticky clay for a 10-15 ton / hour feed rate?  

2 years ago
David 2 years ago

Without seeing his operation, my first recommendation is add more water…

If no amount of water cannot get rid of the clay then you have to go with a more crushing/grinding option. You can go for a ball mill and maybe try operating it similar to a lime slaker which entails more water than conventional ball mill application. Depending on the hardness of the clay this may or may not work. Caliche clay can be pretty hard depending on how dry it has been.

Craig M
2 years ago
Craig M 2 years ago
1 like by David

Part of your selection criteria may be guided by exactly what you are planning to do with the tailings, downstream as you say. If you are planning something that would benefit from new mineral surfaces, even to a small part, you could pass the material through a small ball mill.

2 years ago
David 2 years ago

Try using a Minerals clay scrubber.

Todd H
2 years ago
Todd H 2 years ago

Agree with Dave, clay usually needs significant water to become flowable as a slurry because you have to hydrate the clay as well as provide a mobile phase.  You may investigate the use of dispersants if water alone wont do the job.

Caliche is a hardened type of clay common in desert placer deposits,


Todd Harvey - Global Resource Engineering

2 years ago
oro 2 years ago

Thanks David, those are good suggestions. It's true that no amount of water or additive will break down (liquefy) the extremely heavy / sticky nature of this material so yes I agree as you say, best to use a specialized mechanical method. 

What’s interesting is the feed stock is very easy to crush or pulverize and break down and screen when it is completely dry which then lends well to making a slurry.  The problem is when the feed stock is damp or wet which makes it sticky and packs into dense clumps from handling and feeding. It sticks to your boots, it sticks to a shovel, it sticks to the loader bucket.  Tumbling inside a trommel barrel liquefies a portion but also makes small clay balls stick together creating even larger clay balls!  The mineral sizer would work for dry feed but I wonder about wet feed (?)

After exhausting traditional wash trommels we started using a small ball mill we have on hand but only gives us about 2 t/h (looking to achieve 10 t/h).  It does a good job of breaking down the clay but but it also shreds the organic debris (leaves, sticks) and assorted trash like plastic which causes issues downstream.  What is preferred is a scrubbing method that doesn’t shred the debris.    

We can work around the debris shredding issue but before investing in a larger ball mill I would love to discover an alternative.  I have heard of specialized trommels that rotate faster than normal or are much longer in length or have internal retention rings, all supposedly which lend to more scrubbing action including chains or steel balls inside the trommel chambers.   I wonder who might know more about some of these details. With that we can build a small model to test.   

2 years ago
Deano 2 years ago

If you have a 300mm wide ring at the bottom of the scrubber section to retain the feed you can cycle oversize rocks through the trommel to act as milling clay breakers.

You would want to have 4 slotted 150 wide lifters on the ring to keep the oversize moving through the circuit.

You usually have 150mm angle iron longitudinal lifters in the scrubber section, allow 1 lifter per metre of circumference.

What you want is to run the scrubber as a semi SAG mill with a high pressure internal spray bar adding the majority of the water in the circuit.

Mill dimensions are usually controlled by what equipment is readily available.

If making from new you look around 2m minimum diameter by 6m long.

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