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Author Topic: Water Column Separators  (Read 18766 times)

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Offline GollyMrScience

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Water Column Separators
« on: March 22, 2009, 03:01:39 PM »
This item is a very simple separator that has real potential if used properly.
I can see that I am gonna have to get some pics to help but I hope this written description will work to start.

Chick could you post the pic of your unit? I know that will help a lot!

In practice these would be better termed a super concentrator as it can be real hard to get clean gold.
Also called an Elutriation Column.

The principle is that a gently rising current of water is introduced into the bottom of a vertical clear tube.
The rising water is controlled so that the light material rises to the top and stays in suspension while the heavies sink to the bottom.

By carefully controlling the flow an operator can keep everything in suspension and the material sorts itself by specific gravity.

The lower heavies are barely liquid while the lighter material forms successively fluffier layers as you go higher in the column.

If you run the unit strong enough to blow the lightest sand over the top the heavies will fluff up more but you run the risk of blowing fine flaky gold out.

There are several commercial units that have been made. The Osterberg "Quick Gold" is well known by people familiar with the principle.

There is a fine screen at the bottom of the column and water is introduced through a valved inlet on the side at the bottom.

This screen helps break up the water flow and keeps material from sinking too low in the flow.

Since this unit relies on a finely tuned water flow the operator can help by doing a few things.

First and foremost is careful classification.

The closer the grains are to the same size the easier it is to adjust the flow. A wide range of sizes will work against you so screening on several narrow margin screens is important.

To really control flow the operator needs to have a dependable source of pressure and volume.
If operating from house tap the flow and pressure are pretty consistent but from a pump the fluctuating volumes and pressures can goo things up.

Even on house flow you may find that you cannot turn the flow rate down enough as the house pressure never changes. If your local pressure is 30 PSI you may find that you cannot keep a stable bed.

Ideally it would be great if you could control both pressure and flow.

After fighting with those variables in a camp situation I finally decided to use a stand pipe. Very easy to construct a stand pipe is another vertical column set beside the Water Column.  Imagine a four inch piece of PVC pipe set on its end vertical like the water column. Start with one about three feet long.  It has a valved outlet at the bottom that is linked to the water column and at intervals up the four inch pipe (mine was every two inches) I had another valve.
The stand pipe will operate like a bypass pressure regulator.

Water is pumped into the stand pipe from the top and by opening and closing valves you control how high the column of water gets in the stand pipe. When the water reaches the desired level and therefore pressure, it cannot get any higher as the open valve lets it out to flow back to your reservoir. As long as you feed it enough water to overflow at the bypass  everything will stay constant and WAY easier to work with.

Your stand pipe will control pressure and the valve on the standpipe and the water column will control water volume.

For most of the work I have done I found that filling the stand pipe to about ¼ to ½ higher than the height of my water column separator gave me optimum pressure to lift material into suspension without blowing holes in the material in suspension. Water under pressure will seek the easiest path and if there is a thin part in the stack of suspended material and not a good, even column of rising water with little over pressure, the water will blow through the thin spot and the material will sort of collapse – losing its nice stratified sorting.

This gets particularly noticeable the more heavies you get in the column. They begin to create a layer of  resistance that makes it harder and harder to get good even flow through without it turning into a seething mass of little geysers as the water pops through that layer in different places.

For best results water should be re-circulated and a wetting agent added to the water especially if working with really fine gold.

You should also be sure that the material you are running is pre-wetted to help eliminate the possibility of floating gold off the top.

Remember you are adding the material to the water level on the top of the column.  The water is constantly flowing over the edge of the column and dry material will have very little time to be wetted before it gets to the edge. For real security you can put a ring of plastic in the centre of the column such that the top of the ring sticks up above the water and its bottom edge sticks down below the surface of the water. Add material though that ring. That way no material can ever get out of the column on the surface tension of the water. It HAS to go under the water.

Add material slowly and let the system establish the stratification before you add more material.

Some people run their unit strong enough to lift light sand over the edge and out. I prefer to run it so that only the dirty water goes over cleaning the material so I can see better but not rejecting any real sand over the side.

The water is strong enough to just barely lift the heaviest material and it will give major fluff to the lighter sand.

What you will see is that there will be a very dark band of material in the lowest part of the column and then a thicker band of dark brown over that and then a very thick layer of light coloured material from the top of the darker brown to the top of the column getting lighter and lighter the higher in the column you go.
After awhile you will notice that material has built up enough to start interfering with the action.

Let the unit run for a few minutes without adding anything to let everything in the column get sorted as best as it ever will.

At that point you keep things running and carefully suck the upper layers out of the unit.

Careful here, as the amount of water and material being sucked out should be the same volume as being added.

You don’t want to get ahead of the water being added.

Once you have sucked out as much upper level light weight material out as you dare, you can pour the unit out into a tub to catch the super concentrate. The tub should be big enough that the dump of water and material does not overflow the tub. You can leave the unit running and wash the rest of the material out – controlling the water with the valve.

Save the stuff you suck out to check for gold loses in case you got a little carried away.

While people use these units to clean up black sands from placer work they are often frustrated because they can’t seem to get any real progress towards clean gold. Often they are already at very heavy black sand placer cons and it is difficult to get to a clean gold split or to even get any meaningful  upgrading.

As I mentioned these units are perhaps better called super concentrators as they rarely can be used to produce a clean gold product.

Nevertheless they are simple to run and the average person can build a workable unit easy enough.

Well this post is getting long. I will add more later.
Time for Chick’s two cents.
What the heck - lets just keep mixin' stuff together till it blows up or smells REALLY bad!

ClickTheYellowChick

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Re: Water Column Separators
« Reply #1 on: March 22, 2009, 04:46:49 PM »
Again, a very good job, Mr. Golly.

Here's the photo you asked for.  That will be 1 cent, please.   <-laugh->



Offline GollyMrScience

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Re: Water Column Separators
« Reply #2 on: March 22, 2009, 06:23:05 PM »
Garnet can be a real pain sometimes. It is very disturbing to see large flakes of gold "floating" on a layer of garnet in a pan. wheel or table like a rock star crowd surfing.
You know the gold is heavier it SHOULD be on the bottom - under the garnet, but sometimes garnet sets up a bed that resists that to the point that gold is obviously getting away. Garnet can be worse than magnetite in this regard.
What the heck - lets just keep mixin' stuff together till it blows up or smells REALLY bad!

Offline Woodspirit

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Re: Water Column Separators
« Reply #3 on: March 23, 2009, 05:20:16 AM »
Excellent description and advise, MrScience. I tip my hat.

Megan,
In operating your "Quick Gold" are you using water supplied from your house tap?
Do you know the average water pressure/flow this unit takes for cons with black sand vs garnet material.
In certain locations of the Eastern US we have heavy blond sands as well. This blond sand can really be a pain to separate.

I love this forum!!!!

Thanks

Offline GollyMrScience

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Re: Water Column Separators
« Reply #4 on: March 23, 2009, 08:41:28 AM »
Woodspirit - if your blond sands are heavy then you may be dealing with something like zircon.
Zircon is very heavy and looks like quartz sand in your pan but just will not pan out.
It will drive ya nuts!
It usually isn't an issue till you start dealing with cons. Panning right to black sand in the field and then back panning and snuffing up the gold will rarely give you any hint of zircon.
When you get to cons though the zircon percentage is upped to the point that it becomes a serious pain.
With a specific gravity of 4.6 or so it is heavier than garnet and for that matter much of your black sand.
It is refractory and can be just icky as heck if you try to do a melt with it in the gold con.
Take a look at the blond sands under magnification and see if the crystals look like little quartz crystals with many of them having points at both ends. Often shorter and stubbier than regular quartz crytals and under magnification look brownish to dark brown though some can be pretty clear. Its weight (Specific Gravity) is the biggest hint though.
If you backwash some con and then feather the pan to see the gold line you will see this brownish trail liping along between the blacksand/garnet and the gold.
In western Canada there is a lot of zircon and one interesting thing is that it is very flourescent - it will glow a beautiful gold yellow under black light.
Very pretty but a pain nevertheless.
It would be interesting to check out Chicks anti garnet system to see if you can get a cleaner split.
What the heck - lets just keep mixin' stuff together till it blows up or smells REALLY bad!

Offline Greg in BC

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Re: Water Column Separators
« Reply #5 on: March 23, 2009, 09:47:01 AM »
 [-1st-] Amazing and fantastically clear information.  Thank you very much Mr Science and Chick for sharing.

I like the idea of a stand pipe to help regulate flow and pressure - great idea and description.

Any thoughts on where to get large clear plastic pipe for the tower portion?

Chick, I think I have seen you mention elsewhere that you use a little suction device to pull off the heavies from below the lights - is that correct?  Do you then dump of the lights or do you keep running with the lights stacked in the tube?

Awesome thread - thanks for sharing.
Greg in BC

Offline GollyMrScience

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Re: Water Column Separators
« Reply #6 on: March 23, 2009, 10:10:25 AM »
When I was running this unit in my lab I used a tap venturi device.
A simple plastic tube that was screwed onto a kitchen tap.
When you turn on the tap it creates a vacuum like a suction dredge does through venturi action.
I used this device to create a vacuum in a standard flask with a two hole rubber stopper in it.
So what I had was the venturi vacuum device on the tap with water running through it and a port on the side of that tube.
Off the port a rubber hose to one hole of the rubber stopper.
The stopper stuck in the flask and another tube coming out of the second hole that was my vacuum inlet.
By creating vacuum in the flask I could suck up material from the column and into the flask.
Worked slick.
The suck was immediate and was not hampered by small chunks as long as my tubes were bigger than the biggest stuff to be vacuumed and by using a pinch valve on the inlet ruber tube I could turn the suck on and off at will.
The original purpose of the venturi tube was to create vacuum as an alternative to more expensive and powerful vacuum pumps for lab filtration.
Simple-bulletproof.

The folks at Action Mining have a slick arrangement using a baby wet dry vac to pull cons off their vibrating table.

What are you using in your system Chick?

As a complete divergence for a sec does anyone else think the word "vacuum" is one of the weirdest works we got?  <-thinking->
What the heck - lets just keep mixin' stuff together till it blows up or smells REALLY bad!

Offline GoldFever

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Re: Water Column Separators
« Reply #7 on: March 27, 2009, 04:22:05 PM »
Interesting, and so simple.

Is this the same type of idea as the gold rocket on the Rotapan site?  but without the bells and whistles?

http://www.rotapan.com/

ClickTheYellowChick

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Re: Water Column Separators
« Reply #8 on: March 27, 2009, 05:30:40 PM »
Excellent description and advise, MrScience. I tip my hat.

Megan,
In operating your "Quick Gold" are you using water supplied from your house tap?
RESPONSE:  Yes.

Do you know the average water pressure/flow this unit takes for cons with black sand vs garnet material.
RESPONSE:  No, sorry, I don't...I just tweak the velocity with an inline ball valve until I see it working right.
<-smug->

Thanks

ClickTheYellowChick

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Re: Water Column Separators
« Reply #9 on: March 27, 2009, 05:40:20 PM »
Chick, I think I have seen you mention elsewhere that you use a little suction device to pull off the heavies from below the lights - is that correct?

RESPONSE:  Yes.

 


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