OT: Free argon idea?

Been doing some research on separating air into it's component gases of which argon is nearly 1%. I see argon is more than twice as heavy as oxygen and nitrogen and will settle to the bottom of a container which brings me to my point: If you set up an air compressor receiver with a distinct low point and rigged a solenoid valve to siphon off the 0.93% or so of your total receiver volume, you'd have mostly argon with a whiff of carbon dioxide for the cost of an extra receiver tank and the metering valve.

About the only problems I can see with the idea is the water that will accumulate at the low spot and there would be some settling time for the argon.

This should be pure enough for welding gas especially if the argon storage is a vertical cylinder to allow further settling and purging of the oxygen/nitrogen from the top.

So the whole concept would run something like this: you use your air compressor with it's tall vertical receiver cylinder as usual, but a microprocessor circuit works out how much air was pumped into the tank to bring it up to pressure (pump run time by displacement). The processor board then purges the water, waits for the argon to settle out, works out 0.9% of the volume pumped in and meters that into the argon storage tank by timing the flow through a capillary.

I'd really like to hear what you guys think about the concept although I realise in the USA you have more options available for gases including owning your own cylinders. Welding gas is expensive here in Australia due to an effective monopoly on supply now that BOC, Linde and Air Liquide are mostly merged and is only available as a rented cylinders. I understand Australian gas suppliers refuse to fill privately owned cylinders ( I could be wrong on this ).

If it were that easy to separate argon from the atmosphere there would be no life on the planet!

The argon in the air isn't 'free', it is in solution; which is why the atmosphere does not just settle into its individual gases layered by relative densities.

...and in about a hundred years, you'd have enough argon to shield a one inch bead.

Oh wait... SAG180 is in Australia, so wouldn't the argon float to the top where he's at?

Chobyn said:

The argon in the air isn't 'free', it is in solution; which is why the atmosphere does not just settle into its individual gases layered by relative densities.

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This is the kind of feedback I'm after, I did read argon is a smothering hazard in confined spaces, maybe there's a suitable membrane material to separate argon from air under pressure but then that wouldn't be fast enough.

The atomic weight of Argon is close to 40 while Oxygen is 16 and Nitrogen 14 so an atom of Argon is slightly more than twice as heavy as Oxygen or Nitrogen, however Argon is a mon-atomic gas while Oxygen and Nitrogen are bi-atomic gases; in the atmosphere Oxygen exists as the molecule O2 with a molecular weight of 32 while Nitrogen is N2 with a molecular weight of 28. You are going to wait a long time for Argon to settle out in the atmosphere; like eternity.

mm58 said:

Oh wait... SAG180 is in Australia, so wouldn't the argon float to the top where he's at?

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With all the summer rain here today it feels like an overhead ocean.

I wish it was that easy.......$85.00 a cyl gets old after a while.....

Hdpg said:

The atomic weight of Argon is close to 40 while Oxygen is 16 and Nitrogen 14 so an atom of Argon is slightly more than twice as heavy as Oxygen or Nitrogen, however Argon is a mon-atomic gas while Oxygen and Nitrogen are bi-atomic gases; in the atmosphere Oxygen exists as the molecule O2 with a molecular weight of 32 while Nitrogen is N2 with a molecular weight of 28. You are going to wait a long time for Argon to settle out in the atmosphere; like eternity.

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Ok so the biatomic nature of O2 and N2 shoots down the density advantage and things go downhill from there (or in this case don't go downhill), that leaves only complicated solutions like using thermoacoustics.

I pay about $38 for a T here in the peoples republic of California. I've been quoted over $100, you need to shop around.

SAG 180 said:

Ok so the biatomic nature of O2 and N2 shoots down the density advantage and things go downhill from there (or in this case don't go downhill), that leaves only complicated solutions like using thermoacoustics.

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Or I guess you could get some gas centrifuges like are used for fractionating uranium isotopes as uranium hexafluoride.

But I think fractional distillation is the cheapest way, which is why that is how Argon and Nitrogen are separated from air.

Method for producing Argon

To separate the components of ambient air (produce argon) compress the ambient air to very high pressure and then cool the compressed air (once in liquid state) slowly release the pressure. The components of the liquefied gases (fractions) will boil off at different pressure/temperature points, collected the different gases as thy boil off.

This process is called cryogenic fractional distillation. It is not very difficult to manufacture a home/small business fractional still capable of separating ambient air, the draw back (danger) is that you will also produce large amounts of pure hydrogen, oxygen and other gasses which are not all inert gasses like argon.

Once you figure your time effort and production cost it is cheaper to purchase the stuff.

Marci

Nitrogen generators that use membrane technology are old hat for separating atmospheric nitrogen from oxygen. For example:

http://www.onsitegas.com/products/products_details.asp?ID=8

Phil

Empireweld said:

I pay about $38 for a T here in the peoples republic of California. I've been quoted over $100, you need to shop around.

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I get my gas frim the local Praxair dealer, who do you buy from? A "T" costs me $85.00 in columbus ohio. What are other guys in Ohio paying?

Brownian motion anyone?

Wouldn't this keep the molecules of air stirred? Such that the air is never truly still?

Hdpg said:

Or I guess you could get some gas centrifuges like are used for fractionating uranium isotopes as uranium hexafluoride.

But I think fractional distillation is the cheapest way, which is why that is how Argon and Nitrogen are separated from air.

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The field of thermoacoustics is showing promise for separating gases even isotopes up to 9% for a few metres of pipe and should be better for longer lengths.

Marcibb said:

Once you figure your time effort and production cost it is cheaper to purchase the stuff.

Marci

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From what I can find on the 'Net, 85% of your air liquefying energy cost is in the compression of the air. I thought if there was a relatively simple process that could be added to an existing air compressor, then the argon would be a by-product of the compressed air anyway. It may still even be possible to make a tiny trickle over a long time with some sort of membrane gas filter but that may get poisoned off by oil fumes anyway.

I'd also heard second hand that liquefying air can be dangerous with the compressors in blast depressions as any free carbon from diesel truck exhausts can cause a diesel explosion in the machinery at those pressures.

SAG,

Your first observation does not account for diffusion and mixing in gases. Gas molecules are whizzing around at a pretty good clip, and this causes them to mix really well. Imagine two rooms with a divider between them. Each room has a bunch of 9 year olds that were just fed sugar and amphetamines. In one room the kids all have blue shirts, in the other, red shirts. Open the divider. All you see is a purple blur.

The easiest (from an energy efficienty standpoint) to separate argon and nitrogen/oxygen, is to use cryogenic distillation. Compress, cool, (to minus 185° C, or minus 300° F), condense and then run the mix through a very tall distillation column. See http://www.uigi.com/cryodist.html

Your insight about using membranes is a good one. However, separating anything (even the red shirt/blue shirt melange) requires energy. You have t pressure up the gas on one side of the membrane, and draw the low pressure stuff off and recompress it so that you could get it into a cylinder.

Uranium isotopes are separated by pumping up uranium hexafluoride (a gas) and applying the pressurized gas to one side of a porous ceramic membrane. The pores are small relative to the mean free path of the UF6 molecules. All molecules in a mix have approximately the same kinetic energy. Thus, lighter molecules (U-235) move faster than heavier (U-238). This slight difference means that the stuff that makes it through the membrate is very slightly enriched in U-235, and the stuff remaining on the feed side is slightly depleted. You have to do this compress and separate process over and over again to get a meaningful enrichment.

To give you and idea of how much energy this takes, I understand that the original Gaseous Diffusion Plant in Kentucky, used to produce stuff for the Manhattan project, used the entire output of the Tennessee Valley Authority's power production.

Separating Argon will be highly energy and capital intensive no matter how you do it.

So Marci's probably right. Pay the $85 and save money elsewhere!

Jim

April first is still 3 months away. :-)
...lew...