[labnetwork] Nitrogen Generation

[Matthew Moneck]

Hi Tom,



We installed a 3000 cfh generator in our facility several years back.  The
installation coincided with the opening of a new facility that was expected
to have increased N2 requirements over our old facility.   After running
the generator for several years, I can say without a doubt it has been
worth the effort and cost.



Our facility currently runs 3 feeds of N2.  We run 99.999% boil-off from
our LN2 tank as “utility N2” for chamber vents, turbo purges, gas cabinet
venturis and pneumatics, and several other applications.  We also run the
LN2 boil-off through purifiers for our “process N2.”  The generator was
installed to run 99.9% “purge N2” for wet deck head casing purges, some
pump purges, and other “waste gas” applications.



The generator was sized for 3000 cfh at just over 100psi, and we nominally
run at 2000 – 24000 cfh on a regular basis (wet decks alone require over
1000 cfh continuous flow).  Even though it was spec’d at 99.9%, we often
produce close to 99.99% N2.  At this rate of usage, we saw an ROI of under
2yrs.  At a higher rate of usage, we would have even shorter ROI, but we
wanted to ensure there was some margin for added capacity.



Our system requires up to 210cfm of compressed air at 110psi.  It uses
pressure swing absorption (PSA) through a carbon molecular sieve (CMS), and
the output of the generator goes to a 1000 gal receiver tank before being
pushed out to labs.  The generator portion of the system is very robust and
has low maintenance cost, but the air compressors can require a significant
amount of maintenance.  Fortunately, ours are maintained by the University
facilities group.  However, I have one word of caution.  Make sure to
discuss the cycle times for the PSA process with the air compressor vendors
to ensure their compressors can handle the application.  In the PSA
process, the N2 generation takes place in one of two towers containing a
CMS.  After the CMS in one tower becomes saturated, the air is diverted to
the other tower, and a blow-down is executed to regenerate the first
tower.  The process is not too dissimilar from a twin-tower dessicant
dryer, with the exception that cycle times are much shorter in the PSA
process.  Our generator cycles every 60sec, which cause the variable drives
on the air compressors to constantly ramp up and down, adding more wear and
tear than expected.  With that in mind, you may want to consider a large
buffer tank in between the air compressors and generator.



Lastly, we also set up our system for at least some level of redundancy.
The air compressor system is mostly redundant, but there can be single
points of failure, such as a power outage.  In such a failure, we have a
cross-over valve that allows the generated N2 lines to be supplied by our
LN2 tank.  We don’t want to run this way for very long, but it gives us
enough time to receive notifications and conserve N2 usage until the
compressors and generator come back online.



Hope this helps.  I’m happy to elaborate further if needed.



Best Regards,


Matt



--

*Matthew T. Moneck, Ph.D*

Executive Director, Claire & John Bertucci Nanotechnology Laboratory

Electrical & Computer Engineering | Carnegie Mellon University

5000 Forbes Avenue, Pittsburgh, PA 15213-3890

Phone:  412-268-5430

ece.cmu.edu <http://www.ece.cmu.edu/>

nanofab.ece.cmu.edu <http://www.nanofab.ece.cmu.edu/>



*From:* labnetwork <labnetwork-bounces at mtl.mit.edu> *On Behalf Of *Ferraguto,
Thomas S
*Sent:* Tuesday, July 26, 2022 8:12 AM
*To:* Labnetwork (labnetwork at mtl.mit.edu) <labnetwork at mtl.mit.edu>
*Cc:* thomas.ferraguto at baesystems.com
*Subject:* [labnetwork] Nitrogen Generation



Colleagues,



Has anyone taken the leap moved to Nitrogen Generation or at least
supplemented with Nitrogen Generation (for 3 9's house Nitrogen)?



FYI... I'm no longer at UMass but there is nothing better for fast feed
back than the Labnetwork!



Tom
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