Fwd: [Open Manufacturing] Fwd: DIY liquid nitrogen generator

---------- Forwarded message ----------
From: "Bryan Bishop" <kanzure@gmail.com>
Date: Jun 9, 2010 10:49 AM
Subject: [Open Manufacturing] Fwd: DIY liquid nitrogen generator
To: "Open Manufacturing" <openmanufacturing@googlegroups.com>, <kanzure@gmail.com>

---------- Forwarded message ----------
From: Eugen Leitl <eleitl@gmail.com>
Date: Wed, Jun 9, 2010 at 8:55 AM
Subject: DIY liquid nitrogen generator
To: cryonics-europe@googlegroups.com, cryonics-germany@googlegroups.com


http://benkrasnow.blogspot.com/2008/08/diy-liquid-nitrogen-generator.html

DIY liquid nitrogen generator

You can generate liquid nitrogen (LN2) in the comfort of your own home
with some parts found on eBay. I have proven that this is possible by
purchasing surplus equipment and assembling it as described in this
post. I spent over a year searching eBay, so these parts are not
really easy to find, but the total bill for the whole system was under
$500. The device consumes about 300 to 400 watts of electricity and
needs no consumables (just atmospheric air). The LN2 is produced at a
net rate of about 1 liter per day. This comes out to 9.6 kWh/liter or
$1.15/liter, which is substantially cheaper than having the local
welding store fill up a thermos (granted the thermos must be cooled as
it is filled, thus requiring more than its capacity of LN2).

The most important part of this system is the cryocooler. This is a
device that employs a thermodynamic gas cycle to pump heat through a
very high temperature gradient. Many of these devices are
self-contained and require only an electrical input to start pumping
heat. The crycooler that I used was removed from a surplus RF filter
which used the cryogenic temperatures to maintain a superconducting RF
filter. http://www.suptech.com/home.htm

The crycooler itself has been fairly well documented:
http://books.google.com/books?id=POLgG5mma6IC&pg=PA75&lpg=PA75&dq=sti+cryocooler&source=web&ots=ZTMqWVv8Pu&sig=HbbSzGgnD3fIFxyKJjxFLuNEa9E&hl=en&sa=X&oi=book_result&resnum=1&ct=result

I converted the cryocooler to be water-cooled on the hot end and
attached a heatsink to its cold end. In operation, the cold end with
the heatsink is inserted into the top of a large dewar. Eventually,
the interior of the dewar gets so cold that the air will condense into
a liquid and drip down to the bottom.

The second key part of this system is the nitrogen separation
membrane. The is a device that accepts normal air, and produces
relatively pure nitrogen. The waste products (mostly H2O, O2 and CO2)
are vented into the air. Information regarding these membrane units is
easy to find on the internet, but good luck buying one! They are
nearly all produced for huge industrial installations, and those
manufacturers will not even return phone calls from interested
hobbyists. Asses! I spent a LONG time searching eBay, and eventually
found a very compact unit, which was perfectly suited for this
project. The nitrogen purity is dependent on the mass flow rate
through the device. This means the flow must be carefully monitored
and controlled. I will make another post that describes some fun stuff
to do with LN2.

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- Bryan
http://heybryan.org/
1 512 203 0507

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