Instructables
Picture of Homemade liquid nitrogen generator
coldtemp320.jpg
ln2 jet.jpg

Did you ever think you could make liquid nitrogen in your own garage? This is an industrial process so how can an individual do this? Still doubt me? Intrigued? Read on.

As a lover of science I tried to think of a challenging project that was out of the ordinary. After going through the internet web and Youtube I realized that no one had made liquid nitrogen in his home. Yes, I did see some videos where some would use a Stirling Cooler from a cryorefrigerator and use this to condense nitrogen on the exterior of the cold-head. While one is making liquified gas, this is done using a prefabricated machine. I wanted to make the machine that liquefies the gas. Furthermore, a cryocooler has a very low production rate. You will only get about 500 - 1000ml per day. On the following pages I will walk you through the basics of how to build your own liquid nitrogen generator. Using easily obtained materials you can liquefy nitrogen or air. The unit cools to -320F in under 50 minutes. The production rate is about 350 cc/hr.

A full tutorial and plans are at http://homemadeliquidnitrogen.com This page goes over theory, thermodynamics and more detail on where to get components and how to build this. This Instructable serves as a general introduction to how this baby is put together.

I have just added a new web tutorial on how to make your own N2 gas from the air. I will add this as a new Instructable in the next few days. You can get a link for it at the end of this one.

I have also built a high-precision cryogenic digital LCD thermometer for this project, which you can buy for yourself. You can see how it compares with an Omega digital thermometer here.

Ok. The video above gives you a quick 3 minute overview of the project. At the end of this tutorial I briefly mention the PSA I made for making the pure N2 from the air for the generator. If you're ready for 320 degrees below zero we can begin...

 
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imsmooth (author) 3 months ago

I am thinking of selling a low-cost, highly accurate cryogenic thermometer that I designed and built. Please see my webtutorial for details at homemadeliquidnitrogen.com

If enough people are interested I will make a run of 10.

Also, as an aside, my daughter made her first video and I would appreciate it if you could just visit her video and LIKE it. Thanks. It is here: https://www.youtube.com/watch?v=c-JSJq9EYO8

imsmooth (author) 16 days ago
Yes. The compressed gas is cooled by the expanded gas. When it expands it is cooler. This colder gas cools the pre-expanded gas even more, which is cooler still when it expands. This process repeats until the gas is cold enough to liquify.
EthanP316 days ago

I understand how the process works but I'm confused by the Regenerative cooling tower.

Does it work like this,

The compressed gas flows through the cooling tower and cools down, if it does not cool down enough to liquefy it will flow back up the PFTE pipe and cool down the gas even more and repeat the process until it liquefies?

en2oh2 months ago

can you give any pointers on where you sourced you CMS?

Btw, I just got my Stirling Cooler up and running. Cooling down as I type.

imsmooth (author)  en2oh2 months ago
I'm still trying to set up my source to get the CMS for everyone. I have not forgotten your inquiry.

Also, I've developed a high precision cryogenic thermometer. You can read about it on my site at http://homemadeliquidnitrogen.com
Ugifer6 months ago

This is a fabulous instrucable, but I do have one concern: do you not find that you condense out liquid oxygen, at least to start?

Oxygen liquifies at a higher temperature than nitrogen and one of the classic mistakes people used to make with the liquid nitrogen traps in the lab was leaving the pump running and drawing loads of air through. You would end up with a big trap full of beautiful blue liquid oxygen and a terrible danger of sudden explosion or raging fire!

In spite of that hazard, you have achieved something that i wouldn't have thought possible at home, so great work there. I would like to say that I will be doing this but I have a feeling my wife knows that it's then only two easy steps from here to liquid-oxygen-barbeque-lighting and would instantly ban me from even trying!

Ugi

imsmooth (author)  Ugifer3 months ago

It takes about 30 minutes to get to a point where O2 liquefies. By then the constant inflow of 99% pure N2 has washed this O2 out. I use an oxygen analyzer to measure the O2 coming out and it is LOW.

telstarpk Ugifer3 months ago

You could use the liquid Oxygen to make a rocket. Theoretically, you could also make liquid hydrogen, but it would take a better compressor, a better insulator and a better container. if there is a spark, though... 3... 2... 1... BOOM! Goodbye garage!

exploded garage.jpg
imsmooth (author)  Ugifer6 months ago
That's a good pick up there. I may have briefly mentioned it but I'm using a pressure swing adsorber to take regular air and make pure nitrogen gas. It Is this pure nitrogen gas from the PSA that I liquefy.
mattvdb imsmooth4 months ago

do you have any details on the calculation of qty CMS used for the PSA system.

is the calculation based on the fact that only 21% of air is Oxygen??

Ugifer imsmooth6 months ago

If you mentioned it then I didn't pick up on it. Does that mean that the molecular sieves were used as a PSA as well as taking out the CO2 & water, or are they separate units? I suppose the PSA must be on the high-pressure side of the compressor so I guess it's a separate unit but I don't have too much background in pressurised gases.

Once again: great method & amazing instructable.

Ugi

imsmooth (author)  Ugifer6 months ago
I'll add a separate step explaining about the PSA

The PSA is a completely different device which I may list is another tutorial in the future. This is only to remove the oxygen from the air. I actually have a separate scrubber removing the water and carbon dioxide going into the PSA.

The scrubber described in the tutorial here is just for removing water and carbon dioxide going into the compressor for the ln2 generator.

The PSA has a working pressure of about 100-120 psi
KumailA3 months ago

Do you think this will work for liquefying air ?

http://www.ebay.com/itm/Cryomed-Model-910-C-Freezing-Chamber-with-Racks-/230857392700?pt=LH_DefaultDomain_0&hash=item35c02c423c

imsmooth (author)  KumailA3 months ago

Did you ever get it?

This is awesome, and I really want to do it, but it seems super-expensive.

Is there to do this more cheaply (even if it means that it'll take longer to make less liquid)?

Please let us know about cost-lowering trade-offs. :)

Thanks!

imsmooth (author) 4 months ago
I asked the supplier what amount is needed for a flow of 1 scfm

I think these are derived empirically
Ωmega5 months ago

Great project, but is it possible to liquify other gasses (such as noble gasses), or is this "reaction" only applicable towards Nitrogen?

imsmooth (author)  Î©mega5 months ago
as long as the inversion temperature is above ambient, you can do this for other gases. You would need to check the value.
ViperSRT3g6 months ago

I'd love to make this, but I'm unsure of how I could put this liquid N2 to work.

liquid nitrogen is used in many shop/industrial applications. I need it for cryo-treating certain alloys, shrinking parts for interference fit, purging oxygen from containers. Freezing corpses...

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Haha, aside from the fact that this would be a great learning project, I can't justify creating a nitrogen generator JUST to make ice cream XD

RayJN ViperSRT3g6 months ago

Very, Very hard ice cream

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MOST vanillin comes from the paper pulp processing industry as a byproduct of using wood in the process. There's more paper made than there are beavers available for industry.

(removed by author or community request)

Sort of like winning the lottery, or getting hit by lightning. Millions of tons of wood pulp are processed and vanillin usually comes from that. Beaver hunting tags are quite limited and a thousand tons of beaver butt may not exist in the entire planet. Confirmation may be bit and miss, but it's a really BIG miss. (Just my thoughts on statistics, not trying to argue with you. I don't like the idea of eating it either so I use real vanilla beans and avoid synthetics as much as possible.)

"Beaver-butt"! Ha! It's actually the fake raspberry flavor that comes from beaver's butts. For those that think we're making this up, just google "castoreum".
http://www.snopes.com/food/ingredient/castoreum.asp

i agree with u:)

rusticator6 months ago

A cheaper high-pressure compressor is www.shoeboxcompressor.com. It is available with 4500 and 3000 max psi for $650 plus an oil-less utility compressor for $50-150 as a front-end. Designed for airguns and paintball. Works well.

imsmooth (author)  rusticator6 months ago
Flow rate is too low
I had looked into yhese
Shkinball6 months ago

What do you do with all this Liquid nitrogen though?

scitch6 months ago

Wow! A SCUBA compressor is $1,500-$3,500 on craigslist!

imsmooth (author)  scitch6 months ago
If you get one make sure it is oil free and has a sufficient flow rate.
espdp2 imsmooth6 months ago

As some folks can get several fridge compressors, is there any good reason that you couldn't run two or more in parallel to produce a better flow rate?

There's a risk they produce significantly different pressures. That can
have unpleasant consequences. If you use several of the same make and
type, though, that can be an interesting idea. They also produce a lower
pressure, tho.

lperkins scitch6 months ago

Should be possible to use lower pressure, but you'll need more insulation to compensate for the slower heat extraction.


flashcactus6 months ago

Great 'ible. I'd build one if I didn't live two blocks away from a
company that makes all sorts of gases, both liquefied and not, and sells
LN₂ at ~ $1.60 a liter. Maybe I'll build one anyway just 'cause it's
cool (and I can liquefy other gases with it, too).

What's the lowest temperature that this setup could practically produce?

You've also mentioned that the steel tubing for the regenerative heat exchanger came in 20-foot sections. Did you weld them together or what?

By the way, the compressor page on your site apparently has a typo:

>a temperature, T, of 32C (273K)

You probably meant Fahrenheit, as 273K ≈ -0.15°C.

imsmooth (author)  flashcactus6 months ago
The temperature should be able to go as low as the boiling point of the gas in the system. Of course, if the inversion temperature is too low you will not be able to cool the gas with throttling. You would need to implement a different method like a turbo expander.

BTW, thanks for pointing out the typo. It should have read 0C like you said.

As far as the connections I think I mention somewhere that I use high pressure tube fittings. I got these from Swagelok.
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