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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) 8 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

grapenut imsmooth3 months ago

I tried; "paraently gotta login ta goog...

evdscheer5 days ago

I am looking for someone who can make a LN2 generator for me. Please contact me on evdscheer@gmail.com!

helzcurrah2 months ago

Hi there,

I work as an engineer for one of the companies that makes Liquid nitrogen. I just want to point out there are some very serious risks with this type of equipment which even the professional companies sometimes fall foul of. My professional advice would be "don't try this without proper chemical engineering training", but since I know you already are, here are some safety tips to consider:

* Never store liquid nitrogen or operate this equipment in an enclosed area, always ensure sufficient ventilation. Nitrogen is an asphyxiate with no smell. The only way to protect yourself is to operate outdoors AND wear a gas composition monitor to warn you if oxygen levels in the air fall below 19.5%

* Make sure the equipment is thermally isolated well as it reaches extremely cold temperatures and you may burn yourself if you touch it. Frostbite may also occur if you spill any cold product on yourself. Always wear full length clothes and insulated gloves.

* If there is any possibility of liquid nitrogen being trapped in a part of the equipment (due to closed valves or ice blockage), fit pressure relief devices. When the liquid warms and expands, it can cause an explosion if there is no escape path.

* Distillation columns take in a lot of hydrocarbons and nitrous oxide with the air. These components build up in the distillation still, and can cause an explosion when they react with the liquid oxygen in the still. Ensure you purge the liquid often enough to remove these contaminants.

*If you are running this in your garage (I know I told you not to), don't enter before you take an atmosphere reading. Make sure oxygen is between 19.5 and 22%.

* Make sure all the pipework and vessel is constructed from clean, oxygen-safe metal. During startup, the unit will produce liquid oxygen before it starts to produce liquid nitrogen. High concentration oxygen reacts with any organic contamination, and even metal can become a fuel source for a fire. Carbon steel is not an appropriate material, stainless steel, aluminium or monel is better. Definitely do not use rubber pipes, seals or oil based lubricants!

* There is a chance the atmosphere around the equipment will be oxygen rich, so take care to eliminate all sources of ignition, such as electrical switches, flames, static on your clothes, sparking tools and anything that gets very hot.

mthayne3 months ago
Argon is the gas that would make life great for millions of us do it your selfers with mig and tig welders. That should be your next project.

You might wish to consider using plastic drainage culvert tubing as a housing for your cooling tower, it s available In a variety of sizes (usually in multiples of 6")

in 10foot and 20foot lengths and typically made of PVC, which is unlike cardboard

concrete form tube won't disintegrate when it gets wet.

nicko03 months ago

i use liquid oxygen for scientific glass blowing. would you help design one for liquid oxygen/

studleylee3 months ago

Amazing. I will do this!!!!

RubenL14 months ago

This is a great piece of work, i would love to buy one if you do make any others! this would help me with school projects and many ideas!

imsmooth (author) 5 months 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.
EthanP35 months 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?

en2oh8 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)  en2oh8 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
Ugifer11 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)  Ugifer8 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 Ugifer8 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)  Ugifer11 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 imsmooth9 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 imsmooth11 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)  Ugifer11 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
KumailA8 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)  KumailA8 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) 9 months ago
I asked the supplier what amount is needed for a flow of 1 scfm

I think these are derived empirically
Team_Omega10 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)  Team_Omega10 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.
ViperSRT3g11 months ago

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

toxonix ViperSRT3g11 months ago

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...

i agree with u:)

rusticator11 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)  rusticator11 months ago
Flow rate is too low
I had looked into yhese
Shkinball11 months ago

What do you do with all this Liquid nitrogen though?

scitch11 months ago

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

imsmooth (author)  scitch11 months ago
If you get one make sure it is oil free and has a sufficient flow rate.
espdp2 imsmooth11 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?

flashcactus espdp211 months ago

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 scitch11 months ago

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


flashcactus11 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)  flashcactus11 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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