My sincere thanks to all those who replied to my question about helium recovery.
I attach below (w/o names of contributors) the 5 responses I received.
Here is a summary/conclusion of what I have found.
1) Helium supply is more limited than I'd thought. It's time for all of us to
look for other jobs! (at least if we're not planning on being retired by the
year 2020) I'm only half jesting of course; you can go to
http://physics.wm.edu/~sher/ajul96.html
and read more about it. It seems that we have about 25 years by some estimates
before NMR & other industries that depend on (liquid) helium become prohibitively
expensive. This is because the cost of extracting helium from whatever source
of gas mixtures is inversely proportional to the concentration of helium in that
mixture. The atmospheric abundance of helium is about 0.0005%, whereas the helium-
rich methane mines (from where all our current helium comes) have .3% helium. So
once we use up all of the helium-rich methane there will be no other inexpensive
sources. What's worse, it seems that about 1/2 of the helium mined each year is
never extracted from the methane sources but released into atmosphere as the methane
is burned up, so whether we conserve the extracted helium or not, the supply will
not be affected significantly at all by our (NMR/MRI) usage.
It seems like a familiar situation in which the people making the key decisions
that will affect those who depend on helium in the long-run are being governed by
politics and short-term expediency.
2) Getting back to the original intent of the post; my conclusion (which is probably
obvious to most of you already) is that helium recovery is not practical for most
NMR labs in the US that are not associated with a university with physics departments
with liquifiers and purifiers, etc. This is all tied to the economics of the situation
of course. I have phoned BOC gases (my liquid helium supplier), and they will not
buy back any used helium compressed into gas cylinders because it's just not practical.
I imagine other helium vendors are the same.
3) A good person to talk to was Mr. Jerry Ostenson at Aames Lab, and he gave me some
ballpark figures for the price of various items needed to reuse helium.
Helium Liquifier ~$300,000 (from Process Systems International (508)898-0369)
Helium Purifier (comes with modern liquifiers & can handle upto 25% air/non-he gas)
Compressor ~$30,000-50,000
Attached below are the 5 responses I've received so far.
Sincerely,
John Chung
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Manager, NMR Laboratories (619)784-7453 (Office)
Dept. of Molecular Biology, MB2 784-7455 (Lab)
The Scripps Research Institute 784-9822 (Fax)
10666 N. Torrey Pines Rd. email: chung@scripps.edu
La Jolla, CA 92037 http://www.scripps.edu/~chung
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Ames Lab (part of DOE) has a liquefier. You could call them at
515-294-5656 to discuss the economics. I think that their balloon
fills a room but haven't seen it. I think that you'd be better
off filling gas cylinders. For us it works great.
The helium ports are connected to a 2" copper pipe through vacuum
tubing. During fills, we don't have to disconnect the one way valve.
Since the helium isn't released in the room, it can't go through the "O"
rings and soften the dewar vacuum. There is a ping pong ball "flow
meter" to roughly monitor fill rates. We can usually get a dewar
of liquid helium within two hours of calling.
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We have several LARge magnets in our lab and boil-off about 700
liters/week, but to date even that has been deemed impractical to recycle.
So I'll be very interested if someone finds otherwise.
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We used to recover/reuse our helium boiloff several years ago. We
don't do it anymore, primarily because the liquifier in our Physics
building was de-commissioned, and they never indicated a desire to
resurrect it.
Here are some brief snipetts to think about:
1) We (chem. building) are about 200 yards from the physic bldg, and we
have 1.5" PVC pipe going through the utility tunnel (quite a project
years ago...to go from the 8th floor of our building to their
building). The PVC went to a "Gas Bag" (aka baloon). I don't exactly
know the size, but it filled an average sized room.
2) Here's how the system worked: The He gas would fill the gas-bag, and
when it got close to full, a contact-switch would activate a compressor,
and it would compress the gas into empty cylinders. The Bag had another
contact switch which turned the compressor off when the bag was empty,
and it began filling again. Once the cylinders were sufficiently filled
with gas, they would run the Liquifier (a white-elephant obtained from
Air Products years ago). The design was rather elegant, but after
dealing with it (rather unpleasantly at times) here some experiences for
you to think about:
a) Whatever you do, don't overpressurize your system...they once closed
the valve to the gas bag without telling us, and the pressure-relief
(quench) valves on the magnet started venting on top of my 360WB
magnet...Liq.He gets warmer as pressure rises...surprise, surprise.
b) Make sure there are also safety, check-valves to protect against
negative pressure in recovery system...one time they left the compressor
on (in manual override mode), and went home. Luckily, I was in the lab
at 9:00 at night when they started _literally_ sucking the helium out of
my cryostats!! The vacuum in the cryostat (and poor O-ring seals @ the
fill ports) totally plugged my fill/vent/quench tubes with ice...THAT
was FUN!!
c) Make sure the benefit outweighs the cost/trouble. Once they
re-liquified my boil-off, they tried to re-sell the liquid back to me at
$2.00 over what Air Products would deliver it for. Also, they were
often sloppy, and ended up with dewars with ice in the bottom, which
clogged my transfer lines.
I don't know of anyone who will "buy-back" the helium gas. Our Physics
Department apparently didn't find that to be an option because they shut
down the recovery system when they quit running their liquifier. Since
Helium is a non-renewable resource, we should be seriously looking into
ways to try to save some of this precious gas.
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First, let me refer you to Bob James (james@dirac.phys.washington.edu) for
more information about our helium recovery system, which is run out of the
physics department. Second, I will drone on about whether it might or
might not be worth it for you do embark on this plan (you can delete this
part if you want). Our helium recovery system was installed in about 1980,
when the price of helium was much greater than it is today (most likely,
helium prices will again rise, but it is unknown when). In the many
intervening years, helium prices have dropped dramatically while the cost
of recovery has remained about the same. For this reason, it is now MUCH
cheaper for us to purchase helium on the outside rather than recover it.
However, I still do purchase helium from the recovery center and recycle
mine for those magnets where I can get away with it for the simple reason
that I think it is a good thing to do, and if I didn't the recovery center
might have to close down. I am absolutey certain that given the current
helium economics, the university would not have built the recovery center
today. This assumes that it would sevice all magnets on campus (1x 750, 5x
500, 1x 400, 3x 300, 3x 200) plus the other campus uses in the physics
department. I know that Scripps is awash in magnets, and maybe you have
enough to make it economical- I will be interested to hear what some other
people have to say about this. Certainly as you scale things up, it
becomes more economical.
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The Physics Dept. at Purdue University has a helium recovery system, but I
don't know that anyone there is on this mailing list - you may want to inquire
directly.