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Hydrothermal Fluid Mining

Extracting metals directly from hydrothermal fluids.
  [vote for,

I have no idea how you could make this idea work, but it would be worth the effort. I'm sure many of you know about "black smokers" on the ocean floor around mid ocean ridges. These are hydrothermal fluid vents, and the so-called "smoke" is actually sulfides precipitating out of the discharging fluid. These sulfides often contain very high concentrations of metals such as gold, silver, copper, and zinc. The idea is to pump the fluid directly into some kind of metal extraction process before the sulfides can precipitate. There are severals problems with this. One, is the very high temp. of the fluid. The other is keeping the minerals in solution while pumping it through pipes; if any minerals precipitate in the pipes, it'll plug up the whole system. Any ideas?
Hrothgar, Mar 12 2004

Bacterial mining http://www.abc.net....trek/4wd/Over43.htm
Extracting gold from gold sulphide using bacteria. [kropotkin, Oct 04 2004, last modified Oct 06 2004]

Alternative gold sulphide recovery http://www.knelson....d-goldsulphides.php
[kropotkin, Oct 04 2004, last modified Oct 06 2004]

GMO Ocean Mining http://www.halfbake...20Mineral_20Harvest
[bungston, Oct 04 2004]


       If we do extract gold sulphide, I hope we use bacteria to extract the gold from it (see link).   

       Pumping solutions with precipitates doesn't sound very good - why not filter off the solids? Alternatively, could we just pump large amounts of acid down and dissolve the metals?
kropotkin, Mar 12 2004

       I don't know which way to jump for this idea [hrothgar]. It goes without saying that economically, these hydrothermal fluids could be enormously important.   

       The flip side is that more and more research appears to confirm that the hydrothermal vents at MOR are absolutely key to the ecology of the seas and thus the globe.
jonthegeologist, Mar 12 2004

       Lots of good metals are dissolved in hydrothermal vent fluids. They come shooting out. The water cools. Metals come out of solution. They precipitate out. They fall on the ocean floor. So why not just go down to the sites of dead smokers (where all the life has died off) and scrape up the ocean floor? All the good stuff would have deposited there.   

       Another option would be to set up structures near the smokers composed of metals such that your desired substance would tend to precipitate out on it or react with it. You could haul these things to the surface like a lobster trap, scrape off all the thorium or whatever, the drop it back down to pick up another load.
bungston, Mar 12 2004

       Some geothermal power plants have the problem that they wash a lot of toxic metal compounds to the surface. If you combine metal recovery with geothermal power generation you may reach break even earlier.
kbecker, Mar 12 2004

       Hydrothermal fluid exits the vent system from between 330C to 380C, can have a PH of around 2.4, and is generally found at very deep locations (7000 or so feet).   

       To keep the metalic sulfides in the solution, you need to keep two things constant: temperature and pressure. Hydrostatic pressure at those depths is what keeps the water from turning into steam as soon as it exits the vent. Mixing with cold sea water (2-4C) is what causes percipitation.   

       If one could find a vent close to a shore (Tonga), you could build a pipe out to the site, drill a few feet into the vent system, and pull the fluid out before it mixed with the colder water. The piping technology is already there. How would you keep the pipe insulated? How would you keep the pressure inside the pipe high enough to prevent steam buildup? What would the inside of the pipe need to be made of to prevent rapid corrosion?   

       For the insulation, we'd use Pyrogel (http://aerogel.com/products.htm). Wrapping the pipe in a Pyrogel sleeve would keep the fluid inside the pipe at nearly the same temperature along the whole trip. Insulation problem solved.   

       At some depth (unknown at this time), hydrostatic pressure would be insufficient to keep the hot fluid in a liquid state. Beneath this point, a pump of some kind would need to be installed to keep the fluid above it higher than the threashold pressure. Pressure problem solved.   

       At one point, I considered depleated uranium as a possible material to line the inside of the pipe with. Unfortunatly, there are a host of environmental and corrosion concerns with using this material. Another likely candidate would be a titanium alloy. The technology for using titanium in this kind of application already exists but hasn't been used in this application to my knowledge. Corrosion problem likely solved.   

       Once the pressurized fluid reached the surface, either at an oil platform-like structure or a land-based facility, it would leave the system through a nozzle. This would cause massive depressurization resulting in steam. The end result should be a metalic-sulfide 'snow' percipitating out into a collection vessle of some kind. Since most of this snow would be salt, it would need to be rinsed off, probably with fresh water, which should leave mostly the metalic sulfides behind.   

       Energy for running the pump could be generated by harnessing the steam at the top of the system. In fact, enough electricity could be generated this way to provide an additional revenue stream.
Rahyl, Jul 30 2004

       I read a short scifi story once about a guy who made a technology to extract metals from seawater. Heinlein, I think. You'd hook this device to the bottom of a boat, sail around the ocean, and end up with lots of money. Of course there was a plot too, but it revolved around this device.
5th Earth, Jul 30 2004

       You could cool the water coming out of the vent and have th sulfides come out of solution at the bottom. then all you have to do is pull them up. no need for insulated pipes. no high temp. corrosion problems (except on the cooling structure but that's a pretty small thing)
RichardT, Aug 04 2010

       My objection to this idea is that when we've wiped ourselves and most other living things off the face of this planet, organisms living in the hydrothermal vents will be needed to replenish it. Therefore, we should leave hydrothermal events alone out of respect for the future of life.
nineteenthly, Aug 04 2010

       //we should leave hydrothermal events alone out of respect for the future of life.//   

       Most hydrothermal vents are short lived. Also, we've gone to all this trouble to evolve.
MaxwellBuchanan, Aug 04 2010

       Getting this hot liquid to the surface is simple. No pump or special piping required (other than steel), just depend on the buoyancy of the hot fluid. But these smokers run for hundreds or thousands of years and the precipitates form structures that can become immense. So why not blow them up and haul them to the surface? Wouldn’t that be far more efficient?
ldischler, Aug 05 2010

       // Most hydrothermal vents are short lived //   

       What, you mean they've got even less time than we have?
nineteenthly, Aug 05 2010

       //What, you mean they've got even less time than we have? //   

       Well, I don't know how long you have.   

       Obviously, having been around for several million years is no guarantee that we'll make it through the coming week, what with us humans being such awful terble things. But hey, you know, we might just get lucky as long as we don' go letting them evil GM crops blow the planet up an' all.
MaxwellBuchanan, Aug 05 2010


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