To follow up on this, I've found there are 3 companies which seem to make
smaller scale helium liquefaction plants. Walt already mentioned Quantum
Design, the others are Cryomech and Quantum Technology Corp. I've gotten
quotes from all three and hope some of this information will be useful to
the community.
We have three magnets that if you include helium lost during fills on
average consume the equivalent of roughly 7 L/day of liquid. The economics
of a recovery system don't seem so good as long as helium stays near
current prices (in the neighborhood of $10/L if we buy 250 L at a time).
We spend on the order of $30k/year on liquid helium and if I did my back
of the envelope math correctly helium would have to increase to slightly
over $20/L for us to get one of these systems to pay for itself in a
somewhat reasonable 6-7 years. I'm of course ignoring potential supply
disruptions in this calculation.
Do note that a system has to be sized for what you use. The various
systems I've looked at are capable of producing from 11-22 L/day (all can
be slowed down), costs go up if you need more or just want to fill a large
dewar faster. It gets filled in a closed loop, though, so you can and
should liquefy continuously.
Here are a few rough numbers, the costs for all three seem to be similar
overall:
System cost: all three systems are in the range of $200-250k installed.
However, that doesn't include infrastructure. You probably need at least
some water cooling, you definitely need at least one and possibly two
three phase outlets. There's also plumbing to collect the helium, and it
was suggested that brazed copper be used to minimize losses.
Space and noise: 2 of 3 systems use a helium collection bag (it can be
added to the third); it's optional with Quantum Technology but they prefer
to use a large storage tank and medium pressure compressor. These are
fairly large and need to be located near where your helium boils off. If
you're planning to collect the boil off during fills (recommended) the
collection bag/tank and storage compressor need to be large enough to
handle it. The standard assumption seems to be that you boil off 10% of
what you transfer, so for our 800 we need to be able to handle the
equivalent of 16-20 L of liquid in 45 minutes. The bag doesn't have to be
quite that large since the compressor can run while it fills. There will
be a medium or high pressure compressor for storing gas that is noisy but
will mostly run during/after fills. There's also the liquefier itself
which is noisy. You ideally want these in a mechanical room or closet and
not your main lab. Finally, there are some limits as to how far the
liquefier can be from it's compressor.
Secondary collection: if you have multiple users/sites, you can install a
second collection bag and high pressure compressor to store that boil off
in standard gas cylinders. It will likely cost $60-70k plus cylinders (one
2500 psi T cylinder is equivalent to roughly 10-11 L of liquid), and each
site may want its own dewar. You have to cart the cylinders to the liquid
plant.
Maintenance: Quantum Design is the only one I haven't heard back from, so
you can use Walt's numbers. As for the others, some parts have adsorbers
that need to be regenerated regularly (every week or two) and occasional
replacement ($1000 every 2-3 years). The regeneration is "free" except for
your time and needing to have a vacuum pump. The compressors need "normal"
maintenance (oil and filter changes, etc.) so figure a few hundred
dollars. I can only guess at frequency since they don't run continuously,
but the shorter interval is 2000 hours. The liquefier itself has needs
much like a cryoprobe: changing the adsorber ($1200-2000) and having the
cold head service ($4500-7000) every 2-3 years.
Helium replacement: the system of course won't recover 100%, so you'll
need to periodically either get a dewar and top up a magnet or buy
cylinders to liquefy into the liquid you need. The cylinders cost more but
you can have a couple sitting around ready to go.
Cheers,
Andrew
--
C. Andrew Fowler, Ph.D. | University of Iowa
Associate Director | B291 CBRB, 500 Newton Rd.
CCOM NMR Facility | Iowa City, IA 52242
319-384-2937 (office) | 319-335-7273 (fax)
andrew-fowler_at_uiowa.edu
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Received on Fri Sep 27 2013 - 10:50:48 MST