Homemade Liquid Nitrogen


As far as DIY cryogenics are concerned, dry ice is easy mode. You can get frozen carbon dioxide at WalMart, or from a nozzle that screws onto a CO2 tank. It’s all very ordinary, and not really special at all. Want to know what’s cool? Making liquid nitrogen at home.

[imsmooth] is getting his nitrogen from a standard tank, sending the gas through a CO2 and H2O scrubber, compressing it, putting the compressed gas in an ice bath, and slowly diffusing the compressed, cooled gas into a vacuum reservoir. When the cold compressed gas is released into the reservoir, Boyle’s law happens and liquid nitrogen condenses in a flask.

As far as materials and equipment are concerned, [imsmooth] is using a PVC tower filled with zeolite to filter out the CO2 and H2O, a SCUBA compressor (no oil), and an almost absurd amount of stainless steel tubing for the precooler and regenerative cooling tower. Except for a few expensive valves, dewar, and the SCUBA compressor, it’s all stuff you could easily scrounge up from the usual home improvement stores.

[imsmooth] is producing about 350cc/hr of liquid nitrogen,  or more than enough for anyone who isn’t running an industrial process in their garage. Check out the video of the build below.

30 thoughts on “Homemade Liquid Nitrogen

    1. I’ll reckon he could, but zeolite can’t filter indefinitely. It becomes saturated. A quick look at google shows it’s not exactly cheap, either. Even the lower grade of compressed nitrogen has far less moisture and contaminates than air, so your filters are going to last much longer.

    2. Probably not the best idea as he’d condense a lot of LOX as well. It’s one of the dangers of working with LN2, LOX boils at a higher temperature so you can accidentally condense puddles of LOX in cryogenic equipment and then have entertaining unexpected fires.

      1. LOX doesn’t burn stuff that easy. It is easily kept in a normal dewar and can be used as a replacement for LN2 in most applications, as long as the cooled device doesn’t get too hot. If it gets in contact with organic stuff, it still needs a flame to ignite it. But once ignited, most oxidizable materials burn quite violently

        1. It’s not a problem in most applications true, and does work fine for most things, but if you dump it like he does in the end of the video and it hits a wall wart that’s running warm or other some high-surface-area materials that are a bit warm, things can get spectacular fast.

        2. Most stuff that barely burns with atmospheric oxygen will burn pretty ferociously in LOX and the well burning in atmosphere tends to explode/flash in LOX…replacing LN2 with LOX is just an unnecessary fire hazard, mostly because you’ll end up with an oxygen rich atmosphere around, which is something that should be avoided…

        3. While LO2 isn’t the boogeyman that it is often portrayed as, be aware that it can still ignite due to compression, friction/impact and ESD. Also, many common compounds such as iron, copper, cromium and nickle can catalyze an ignition event.

  1. Cryonics (from Greek κρύος kryos- meaning icy cold) is the low-temperature preservation of humans who cannot be sustained by contemporary medicine, with the hope that healing and resuscitation may be possible in the future.
    For the study of the production of very low temperatures, see Cryogenics. For the low-temperature preservation of living tissue and organisms in general, see Cryopreservation.

    1. Oxford dictionary:
      plural – noun – [treated as singular] the branch of physics concerned with the production and effects of very low temperatures. -> another term for cryonics.

      1. I have a dictionary that states that oxygen is the most plentiful substance in the universe. Never rely on dictionaries for information about science.

        1. The Oxford dictionary is what every English speaking country uses to define their words in both law and academia, including the US. Accurate or not, if Oxford says so, then it is true.

          1. For clarity, cryogenics and cryonics are different words of course
            Here’s the entry on cryonics:

            plural – noun – [treated as singular] the deep-freezing of the bodies of people who have died of an incurable disease, in the hope of a future cure.

            And for completeness:

            noun – a substance used to produce very low temperatures.

  2. This opens the doors up for a ton of high-tech hacks, since obtaining liquid nitrogen kind of a pain if you aren’t near a university you can swipe some from. I’m thinking custom made overclocked PC’s cooled by LN, and quantum-locking cat toys. Most high temperature superconductors are ceramic, so it might be possible to 3D print the ceramic powder using a paste extruder. It would also be cool to demonstrate lens’s law using a superconductor instead of the usual magnet + copper pipe.
    I haven’t done any research into any of these ideas yet, so take my words with a bag of salt. The skies the limit, until you learn about the tyranny of the rocket equation.

    1. Cattle breeders keep liquid Nitrogen for storing-shall I say “Bull juice.” I once picked up a tank of LN for a cattleman friend of mine. The people at the facility told me the story of someone who picked up a tank of LN and put it on the seat next to him in his truck. He was in a car crash, and the tank came open, sloshing LN onto his chest…Needless to say, I stored the Dewar outside the cab of my truck.

  3. You have to be careful with open containers with liquid nitrogen. The liquid is cold enough to condense oxygen out of the air, and it will float on top of the nitrogen. Liquid oxygen can be very dangerous in combination with flammable materials.

  4. I’m wondering about the cost per cc (or L). Just /how/ cheap is this process to run? And what is the cost of construction? I just wonder if it is “cheaper” to produce than commercial LN2? Not, as other people have mentioned, that LN2 is actually easy to source in 1L quantities.

    1. In most US cities, you can get LN2 for between $0.30 and $1 /liter. Just go to an Airgas or whatever with a dewar and they will fill it right up for you. I do it all the time.

  5. Possibly a dumb or Uk-centric question but why scrub it? A W-size tank of nitrogen (9.5m3 of 99.998% N2 ) costs about £23 which is only about £2 more than the equivalent sized bottle of air. You won’t better almost 5 9s purity unless you do something fairly cunning.

    1. such pure N2 will cost a lot more then technical grade (or maybe his supplier doesn’t do super-pure?)…also, what would the delivery and tank rent cost be?

  6. I worked on a unit in a plant that sucked in plain air and got it cold enough that the O2 condensed and then the N2 condensed out, the other stuff was rejected or scrubbed. The N2 went for pneumatic devices and the O2 went to be combusted in a cogeneration-turbine-generator rig.
    Lots of heat exchanger stuff going on. To get it started you need a charge of liquid N2 though. In the end they just wanted clean gaseous N2 and O2 and the easiest way wa the cryogenic route.

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