Time of flight separation of gold from creek sand

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Time of flight separation of gold from creek sand

Postby Bill Fain » Fri Oct 29, 2010 8:01 pm

OK, I went gold panning for a few days in western North Carolina. I have some gold particles and supposedly a lot more in the concentrate I am going to pan in my leisure time at home. I have about 3/4 of the commercial parts I need to build a Keen "high banker". A device that separates the dirt and rock from the gold bearing sands (also uses a sluice). The high banker has a port in it that you can retrofit the rest of the stuff you need to make it into a "dredge"; basically a big wet vac. My question/Statement is this: Could you separate the sand, pebbles, and gold into specific bins using the concept of a mass spec? I would assume that you would take the output from your dredge hose and run it into the straightening vanes and then into a sorting plenum or chamber, maybe the heaviest stuff would fall first, then the next heaviest etc. I realize that specific gravity is not the only thing in play here as particle size ,momentum, water currents, and turbulence also enter into the equation. Your bin heights would have to be adjustable as well as their spacing. Also you would need a trap door or valve to empty each bin. Does this sound plausible or is a "half baked" idea that won't "pan out". -bill
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Re: Time of flight separation of gold from creek sand

Postby Joe Jarski » Fri Oct 29, 2010 9:01 pm

I think all of the other factors that you mentioned would make that method near impossible. Something similar that I've pondered over is whether eddy current separation ( like that used in waste recycling ) would be effective in that application, but there may be enough minerals mixed in to make that ineffective too.
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Re: Time of flight separation of gold from creek sand

Postby Bill Fain » Fri Oct 29, 2010 10:15 pm

Joe, Hi. That was a very interesting video. Wonder if it works that good in real life? Seems like any moisture at all would change things considerably. Getting back to the gold separator. I visualize that maybe some bins would have a combination of things in them that combine to create an equivalent "buoyancy". Don't know if that's the right word or not. That might help some. For example you might have some small gold flakes and some bigger less dense items that have the same amount of drag, fall into the same box. Any degree of separation would be helpful. I would imagine that if it was easy to do, someone would do it by now I guess. With the recent climb in gold prices, there could be renewed emphasis on things like that. I know that old mines that were closed years ago are now being re-opened because they are now suddenly economical to operate. Thanks for the comment. -bill
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Re: Time of flight separation of gold from creek sand

Postby chrismb » Sat Oct 30, 2010 1:36 pm

Hey Bill. Are you doing this for the interest of how you might go about separating the stuff efficiently... or just want a straight answer and your hands on the gold!?

Some time ago I was involved in surface-wetting research, with one major end-use being the froth-flotation separation of minerals. You are basically separating materials out according to their hydro[phil/phob]icity. This is how Big Industry does a lot of its mineral separation. Might be worth an amateur-have-a-go to see how it works out on a small scale.

cheers,

Chris MB.
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Re: Time of flight separation of gold from creek sand

Postby Bill Fain » Sat Oct 30, 2010 2:44 pm

Chris, Hi. Yes and yes. I have been watching You tube videos this afternoon on how some "good ole boys" go about separating out black sands etc. Combining some of the methods in a closed loop system with various surfactants etc. might be the prize. I was originally doing a little tangential thinking (that's all I mostly do anyway, ask Doug) about gold separation and I was wondering about any parallels to fusors etc. That's when the idea of the mass spec method hit me. Immediately after I thought of it, I realized all the reasons it probably won't work. The water turbulence and currents created by the interference of each particle in relation to the other being the main ones that come to my mind. Who knows, maybe these interferences can be minimized somehow by clever engineering. I don't know much about magnetics or electrostatics and tend to try to make everything into a "water" analogy anyway. I did have a course in fluid dynamics and understood a little of that; I tend to use what I know or at least what I "think" I know. Heck, this is the "water Cooler" section anyway. Come to think of it, Doug's fusor displays some pretty interesting phenomena at the junction of the 6" pipe and the main chamber; Turbulence? -bill
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Re: Time of flight separation of gold from creek sand

Postby Doug Coulter » Sun Oct 31, 2010 1:02 pm

Yeah, Bill's tangential alright, but usually in a good way. Explaining to him how he's wrong makes me think better, so it's a bonus ;)

Forgetting surfactants for the moment...I've seen some amazing floatation chemicals that are so dense normal rocks float in them, and this is a fast process. If it floats, you wash it away (catch in a filter and recycle the fancy heavy liquid/slurry). Now you are a lot more concentrated....think U enrichment which takes many steps with a little improvement at each one. The farther apart the densities, the faster you can run a process and still get decent separation. Not to mention, the evenness of the "fineness". For example, at very fine grits, it can take quite a long time (hours) for a heavy solid to settle even in still water -- this is how you grade some abrasives. So very fine stuff will tend to float, and if it's gold, it will be lost (think how it acts in GoldSchlager) if you go too fast. Once things get to "sand size" it's not so much a problem unless you're going really fast and with a high Reynold's number (turbulence).

A lot of the surfactant stuff is mainly used to separate fine from coarse -- the fines get caught up in the bubbles regardless of density. You might not want that?

So you might want to start by separating by size, or crush to uniform size.

At any rate, to combine fast with effective, think about a multi-stage setup where it just gets better each stage -- by the last one, there's not much left (unless you are insanely lucky and it's all gold), so it will naturally be able to go slower if it's the same size.

At some point....the old mercury method comes to mind for these small amounts (again assuming one isn't insanely lucky). A solvent beats a surfactant any day.

B&W has designed and has data on some related stuff that separates coal and rocks -- important to coal-crusher life etc, but the same problem in another guise. Miners in general do some version of this, only super rare stuff gets hand-cobbed (or in places where labor is real cheap). I'd be looking for tricks for ore enrichment from anywhere in the mining business -- the same tricks will more or less apply here, modified to suit the densities involved.

I easily pulled all the black sand out of a gold dust sample for another guy the other day with a magnet. The trick there is to go slow too, and shake the magnet to get all the gold dust loose off the black (iron oxide, magnetite) sand before pulling out of the top of the vessel. Near perfect separation in a few seconds, after he'd worked it with a pan till he was blue in the face and couldn't get that last bit out of the gold (about half the volume). So you might think about a combination of techniques here....

After all, if you can get to a place where you remove 5% of the junk, but zero gold per pass -- you can get there fairly quick.

Now if you want truly tangential -- how about eddy-current braking that would only work on electrically conductive stuff. Get out that superconducting magnet! Of course, you'd have to separate the iron compounds in another stage.
Posting as just me, not as the forum owner. Everything I say is "in my opinion" and YMMV -- which should go for everyone without saying.
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Re: Time of flight separation of gold from creek sand

Postby Bill Fain » Sat Nov 06, 2010 6:07 pm

Hi, Just can't let the gold thing go. With the ever increasing prices and the need for hard assets, I think about it a lot. I also think about perpetual motion , but I know that's a loser. Toward that end, here is the "Lowes Sluice" or the "Home Depot Sluice" or whatever. I constructed this in about an hour with minimal tools and parts from the building supply (10' corrugated drain pipe, two 2X4s, one 2X10 and some expanded metal gutter guard) Only about half of it is covered in the expanded metal because I don't know if it will fill up the grooves and not let anything else in or not. I plan to deploy it on a non navigable, non fishable, stream that runs through the center of my property in Woolwine, Virginia (catchy name,huh?). I plan on leaving it through several rains and come back and pan its contents later. In this way I'll be able to determine from the contents if it's worthwhile to come back later with a high banker or dredge. That assumes the good ole boys up there don't shoot it up or steal it as they have done to stuff in the past. My question to you is this: Should I put an inlet grate on the front and cover it with gutter guard (shown diagonally) to keep big stuff out or just let it be open and let everything try to make its way through it (note: I plan to fill in the little "pie piece" gaps in between the pipes and the wood). Regardless, I figure there will be no less than a few branches, beer cans, or big rocks clogging it up anyway (assuming it's still there when I return) -bill
IMG00018-20101106-1612.jpg
Lowes Sluice
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Lengthwise split corrugated pipe in place
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Expanded metal leaf guard in place
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Re: Time of flight separation of gold from creek sand

Postby chrismb » Sun Nov 07, 2010 4:14 am

Bill,

If you are going to be constructing things in the stream, then you might also like to consider experimenting with staking out a sheep fleece.

This goes back to the Greek tale of the 'golden fleece' and, as far as I have heard, has been a method practiced in various ancient cultures;

http://en.wikipedia.org/wiki/Golden_Fleece#Gold_washing
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Re: Time of flight separation of gold from creek sand

Postby johnf » Sun Nov 07, 2010 3:25 pm

Bill
My father was concerned with an iron sand operation where the barge floated in its own pond and it dredged the sand and concentrated the iron sand by spiral separators then magnetic separators giving 99% iron sand as output. The other output of course was ordinary beach sand that was dumped at the other end of the pond. This way the dredge moved up and down the beach removing the ironsand and returning the beach back to normal condition
Do a google on spriral separators.

PS I found this when looking
http://www.desfox.com/

Looks very good for your last stage operation
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Re: Time of flight separation of gold from creek sand

Postby Bill Fain » Sun Nov 07, 2010 5:02 pm

Chris and John, Hi. Chris, I was trying to figure out how to integrate carpet into the sluice as most sluices use it. Staking the carpet right in the creek bed is a great idea. Someone said the old 1970's era shag (a form of carpet, not what you do on it) carpet is very good for snagging gold. 3M makes something called "Miners Moss" that also works. I will use wooden stakes so my "buddies" will have no reason to pull it up and sell the metal. Randomly placed stakes or maybe even small stake "dams" might help with deposit of materials in the rug. Using enough stakes to form a Venturi on the rug might be interesting as well; as deposits may occur in the outlet as the flow slows. Of course a heavy rain could wash everything under the carpet (pun intended).
John, There is some iron scattered around near Doug and I. One of the towns between us is named "Ferrum" and iron was mined there for the civil war. I wonder if a rare earth direct magnetic mining system could be designed to pull from the creeks. The cost of iron ore keeps going up. When I ride my bicycle on the highways, I see a lot of "road kill" metal on the shoulders. I have also wondered how much could be harvested from the sides with a big magnet. I have been looking into the spiral gold wheels. One of the "miners" I know (actually a double major Chem E and EE from Princeton, that worked at Bell Labs) has worn out three of these wheels concentrating black sands. I have also thought of a linear "decelerator", made from cyclone separators in series. Quite pricey just to test though. Another idea I have is to make a sand screw and use it to pull up debris from the bottom of the stream and push it through a sluice. It would consist of something like This encased in a 4 inch OD pipe. I would have to have part of the auger sticking out past the pipe and maybe put a metal nipple on the end of the pipe. Thought about using plastic to test the concept to start with. I guess the pipe could rotate along with the auger. Somewhere along the way I will have to somehow contend with friction and sealing. -bill
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Cyclone Separator
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