99.5%? Is it possible?

[HAuCl4]

Thanks 4metals as usual. 8)

 

[qst42know]

The spray nozzles used for atomizing must create a considerable draft of air. Does this process require any sort of shroud?

 

[4metals]

There is some spray and the top of the receiving tank is sealed with a lid leaving the only opening, which is where the stream of gold is delivered to the high pressure stream.

 

[HAuCl4]

I believe a relatively cheap atomizer can be built using a second-hand SCUBA air compressor attached to a cascade, attached to an air-water tank, attached to the water cleaner nozzles, delivering the spray into the receiving tank. The air cascade would keep the pressure constant for a steady spray.

http://www.northshorecompressor.com/cascade-systems/cascade-systems.html

Instead of tundish (to make it simpler), an electric kiln at around 1200 C, with a graphite crucible with a small hole (or several for a larger multiple nozzle system) in the bottom, fed molten metal from the top, would provide a relatively steady metal drip into the atomizing nozzles.

A little trial and error would be expected for a first time builder however, and a safety warning about the high pressures used and the pipes, tanks, valves, etc to handle the pressures safely. This isn't something to toy with. :shock:

 

[4metals]

The crucible with the hole in it is exactly what a tundish is. It's pretty simple already. I happen to know a bit about scuba diving, I've been doing it for 40 years, and there is no way a cascade system will be cheaper than a 5000 psi power washer.

However 4, 1250 psi washers will be cheaper than 1 bigger one and the plumbing will not need to withstand the same 5000 psi so it can be threaded pipe. Just run the pipes so they form the same 4 jet configuration and make sure all the 4 washer can be turned on at the same time.

 

[HAuCl4]

Obviously we have a confusion. I understood the system operated at 5,000 psi. Now you say that it operates at 1,250 psi?. That would be certainly cheaper. 4 water cleaner systems at 1,250 psi would deliver higher flowrate, but they wouldn't take 5,000 psi of pressure. I'm confused about the specs you quoted above in one of the earlier posts.

In my head I was building a 5,000 - 6,000 psi atomizer, not a 1,250 psi one. :shock:

Here's a link for several 5,000+ psi pressure water washers. Probably a used one is cheaper.

http://www.ultimatewasher.com/5000psi-gas-powered-pressure-washers.htm

 

[4metals]

A 5000 psi pressure source will supply 4 nozzles which each have 1250 psi of pressure and 1.4 gpm of flow (each) The 5000 psi is what is delivered to the manifold before it is broken down to the individual spray nozzles. I suppose you could use 5000 psi per nozzle but you may make powder so fine it will never settle.

 

[HAuCl4]

I see. So the system operates at 1,250 psi of maximum pressure and 1.4 GPM of flowrate per nozzle. Thanks. 8)

I used to teach fluid mechanics at a university 25 years ago, and design protection for pipe systems against water hammer events, but there you go, I still managed to get confused about pressure and flowrate. :lol:

IMHO a 5,000 psi pressure source would destroy equipment designed for 1,250 psi unless the designer used a very generous safety factor. Pressure at the manifold is likely a little over 1,250 psi and the manifold simply distributes flowrate. A technicality over which I'm not ready to start world war III with you!.

 

[4metals]

Well I never taught fluid mechanics so I'll defer to your wisdom. I do know that I've personally seen manifolds supplied with 5000 psi of pressure with 4 individual 1250 psi nozzles at 1.4 gpm coming off to form the 4 nozzle arrangement to atomize the metals.

It used butt welded schedule 80 pipe fittings for a manifold. I was told that these fittings are in excess of the requisite 5000 psi and the welds were x-rayed to assure they could take the pressure.

I assume, and while assuming can get one into trouble in this case I feel relatively safe, that the maximum pressure the manifold sees is the output of the pressure washer. That pressure is vented in 4 places with the nozzles each rated for 1250 psi. So the manifold can take 5000 psi but I doubt it ever sees close to that.

 

[HAuCl4]

I see. The pressure inside the manifold depends on the pump and the flowrate. The pump (probably a reciprocating pump), if one attaches a wide hose to it (with no backup resistance to flow), the pressure delivered is basically zero (the reading of a gage at the manifold at atmospheric pressure). If one restricts the flow with nozzles, or a valve, or whatever, then the pressure rises to the maximum limit the pump is capable of (most have a bleed off safety valve to prevent self-destruction, or a shut down mechanism).

If what you saw was a max 5,000 psi machine attached to the manifold, then the pressure in the manifold (and each nozzle) could get close to that. If however a 1,250 psi machine (or four of them in parallel) were attached, then the pressure in the manifold could be close to 1,250 psi.

The way nozzles work is that, for a certain flowrate, a certain pressure drop across is needed. This is the 1,250 psi drop at 1.4 GPM that you quote. The pressure at the discharge point of the nozzle is zero (atmospheric pressure), all the energy has been converted to fluid kinetic energy. This speed is what cuts the metal. In the inside of the nozzle, and towards the manifold, the pressure is 1,250 psi only if the flowrate is 1.4 (for that quoted nozzle). If one forces more flowrate through the nozzle, the pressure drop is bigger. If you put a 6gpm nozzle, the pressure drop would be smaller.

It's not clear to me just yet what the atomizing pressure is. Was there a pressure gage at the manifold?. What was the pump used 5,000 psi pump or 4 pumps of 1,250 psi?. :?: Of course the lower the pressure, the cheaper the system. Also the less dangerous.

If the flow rate at 1.4 GPM measurement is accurate, then the most likely pressure in the manifold is 1,250 psi. If you put 5,000 psi to that same nozzle, then the measured flowrate will be bigger.

 

[Lou]

The chlorine reacts with everything but the gold (and PGMs present). Gold chloride is not stable thermodynamically at that temperature. The silver, copper, and other base metal chlorides are either volatile, or float to the top as a slag that is bailed off. The resultant gold usually clocks in around 3N. Bear in mind that the AgCl so produced must still be smelted to silver and then the slimes processed for accountability on the gold.


Lou

 

[qst42know]

From this link the pressure should be closer to 13.7 MPa, 40L/min (1987 psi, 10 gal/min).

http://books.google.com/books?id=6aP3te2hGuQC&lpg=PA102&ots=wO3JDSW_Vc&dq=water%20atomizing%20precious&pg=PA105#v=onepage&q=water%20atomizing%20precious&f=false

 

[FrugalRefiner]

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