Hello All
A while back I asked if people wanted to share info about things they have
done or learned installing Helium Recovery. (original email at bottom).
I only got 2 responses so I will list them here instead of trying to write
a summary of just 2. If anyone wants to reply now I can send out something
again later.
1:
Quantum Technology medium pressure system installed here at McGill
University in April, 2021. We have a 20L/day liquefier with a 150L
production dewar, and a 200L transport dewar. Purification is by LN2, and
there are 7 medium pressure storage tanks with a total volume equivalent to
60 liquid litres. The system collects from 6 low field magnets (300-500
MHz) and one pumped 800. Total liquid helium usage per year ~ 2700L.
We used the Veiga ProPress 2" copper pipe, and it seems very good. We have
no problems with purity, and no leaks (other than one fitting that was not
crimped which we found the first time we tested the piping). We aren't
collecting quite as much total boiloff as we expect, but since we don't
lose anything during transfers (ie when pressure in the pipes is higher
than usual) we are sure there is not an issue with the joints. We don't
have any fancy manifolds- 20ft of 2" stainless flex goes from the exhaust
to the copper recovery header, and that is sufficient for warming active
boiloff. The frosting helps with knowing when a fill is over, but the
absolute best way (for magnets without a reliable level meter) we have
found to monitor is to watch the pressure in the recovery header, which
jumps significantly when the magnet is full.
The LN2 purifier seems to work very well, and the inlet purity is always
well above the limit, so we think the piping is very clean. We are still
figuring out the exact regeneration period. The main issue we have had
lately is that since the last regeneration the weather has been very humid,
and the building AC does not take it down to winter levels, so there has
been a lot of ice forming around the neck where there is a small flow of
cold nitrogen gas escaping. Even the exhaust pipe got very covered in ice,
but we have extended it and have a fan blowing gently on it now, which
keeps the ice down.
We purchased a scale to keep our transport dewar on (as it doesn't have a
level meter). That has been a bit tricky to sort out, as it is digital and
doesn't necessarily deal with slow changes in weight. But with some
additional instructions from the manufacturer we seem to have got it able
to measure changes of 1 lb or so after switching it off and on. Between
that, knowing what we have in storage, and the dial on the production dewar
the numbers add up to within 5L, allowing us to know how much helium is in
the system.
We are really happy with the direct to medium pressure storage option. The
liquefier constantly takes in the passive boiloff, producing around
6-8L/day, and during a transfer the medium pressure compressor turns on to
direct the excess into storage. The liquefier then ramps up to 20L+/day
until the storage is emptied.
It has taken quite a lot more of our time to monitor and figure out than we
had anticipated, it is a lot louder than we thought (sound proofing a work
in progress, potentially an expensive work in progress!) and there are a
number of small fixes to the HMI interface (which allows communication with
and monitoring of the liquefier and compressor) on our wishlist (and they
mostly will be incorporated on an update).
And finally, it took us a few unexpected events to appreciate- but if
something goes wrong and the system shuts down ... the worst that happens
is the header pressure goes up to 0.5psi and the mechanical relief valve
opens up and we lose some helium. But not nearly so much as we have already
saved by having the recovery system! This has happened a couple of times,
and the magnets are fine. The liquefier compressor seems a bit sensitive-
but the recovery compressor is not- so although there have been a few times
that the production dewar started to warm up because the compressor turned
off, the boiloff got passed back into storage. We can log in remotely to
check that everything is running (via a laptop we have connected to the
HMI), so when there is an issue we usually find out within 24 hours or so.
We are definitely open to questions and have a website at
https://mcgill.ca/mc2/helium-recovery-system
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https://urldefense.com/v3/__https://mcgill.ca/mc2/helium-recovery-system__;!!KwNVnqRv!V1iYu6PyAol0IBEaDKoJzXLvyzy_HRfr29VyOZl3csz13-6--6ipi5j-AHzjo3Ot$>
with
some information.
2:
Here at the U of Vermont (UVM) we have 2 500 MHz NMRs in a lab with an EPR,
which will get occasional helium cryostat use, and the faculty member who
got the supplemental NIGMS grant for the recovery system does magnetic
circular dichroism (MCD), which has a supercon magnet which gets ramped up
to field when they need to do experiments.
As for the HeR system, it is a medium pressure system, which uses a helium
storage bag, with a LN2 purification system. I think this is called a
'manual' purification system, we couldn't afford the automatic one. We
purchased the system from CryoMech and it has the capacity to produce 15
liters of liquid per day.
The system was installed July 27-29 and I'm still grappling with figuring
out the LN2 fills for the LN2 purifier trap. We haven't had to replace the
trap yet and our numbers for the purity have been good so far (<10 nA, and
lately as low as 2.x nA). At this point we likely don't have enough helium
in the system quite yet, and are planning to add more, but the recovery
lines for MCD and the EPR have not been installed.
After seeing several different designs for manifolds for the NMR magnets,
we used the design and materials that you recommended, although I did have
several other very helpful interactions with other NMR facility managers
who went through the same thing. And received photos of manifolds from
several places, which were very helpful.
I've tried to answer all the Qs that you posted, let me know if there's
anything else. As you know, still figuring out the system and all it will
take to maintain it!
3:
Ours here at TAMU is mostly on our website, still working on it:
https://nmr.chem.tamu.edu/HeliumRecovery.php
Original email:
Howdy Everyone
I know a lot of you out there have just put in or are putting in Helium
Recovery systems. We have been using ours for almost a year now. In the
last several years there have been several emails here and I have gotten
personal emails from people too asking questions or wanting advice. I know
there are several locations trying novel things in their installs such as
crimp fitting copper or other materials. Also, sites using different
designs, no back pressure controllers or maybe heat exchangers or not.
So I was hoping that people could share updates on what they have done, or
are planning, and how things are going with either the installs or overall
functionality of their systems. Maybe a short description of how many
systems you have and the layout? Are you using High Pressure Recovery or
Medium? What type of purification system do you have, LN2 or ColdHead? What
materials you used, and how you think things are functioning? What
pros/cons have you found? If you have any info on your purity or efficiency
that would be great too. If you want to share info on the amount of gas
being processed or liquid amounts being made? Do you have information
posted on your website?
Basically anything you would want to share would be nice to hear. I would
be happy to compile the responses and post a summary later.
2 examples of things we have experienced and liked:
1. We went with LN2 purification due to initial costs, water and electrical
needs. But there was not a lot of info out there about how well this
worked. After some initial system issues (leak in compressor) that were
causing us to change the LN2 trap every 48L of liquid made. We are very
happy with the LN2 system and can easily go 2 months without changing the
trap now!
2. This is a nice problem to have, but we did not think we would be having
to take liquid out of the liquifier so we can have room to make more
liquid! It took us a little while to get into a routine that seems to be
working for us. But we do more 20-30L fills more often instead of waiting
and going fills that use 50-60L. Basically we have 1 fill a week happening
now (DNP gets filled every other week) instead of several weeks off and
then doing 2-3 in a single week.
Greg
Gregory P. Wylie, Ph.D
NMR Facility Manager
Texas A&M University
Department of Chemistry
P.O. Box 30012
College Station, TX 77842-3012
gregory.wylie_at_chem.tamu.edu
979.458.0705 (voice)
979.845.4719 (fax)
706.206.0007 (cell)
http://nmr.tamu.edu
Received on Fri Oct 08 2021 - 06:08:25 MST