liquid nitrogen generator

rocket100, how exactly is that going to store energy? You couldn't create a magnetic field dense enough to store any practical amount of electricity. It'd be more efficient to use the liquid nitrogen to power a Sterling engine.

... back to the liquid N2 issue

I found an textbook that details one particular process to make liquid nitrogen.
The fundamental process is just like a normal air conditioning or refrigeration system. The idea is to use an initial refrigeration cycle to provide cooling for a subsequent cooling cycle of a different gas, which has a lower liquification temperature.
First, you compress ammonia, NH3, and expand that product through a valve or orifice to get to about 240 K. The liquid NH3 is used to liquify ethylene gas, C2H4, which will evaporate at 169 K ... requiring compression to 19 atmospheres. The liquid C2H4 is used to liquify methane, CH4, which yields an evaporation temperature of 111 K ... requiring compression to 25 atmospheres. The liquid methane will provide a cold enough product to liquify nitrogen gas when it is compressed to about 18 atmospheres.
One approach to achieve the goal might be to get several compressors similar to those used in the scuba tank refilling process. You would have to have a different compressor head for each gas, but you might just require one motor or engine if you could arrange a separate drive belt to each compressor head.
The one other technical difficulty to be worked out would be the necessity for several heat exchangers. These HE units would have to be physically able to hold up to the respective working pressures of each gas. It may be that you could find some surplus industrial heat exchangers someplace. There might be some type of automotive or truck radiator that would serve the purpose. ..... At any rate you would probably want to have some kind of blast shield or protective wall to use when you first turned the switch on.

The only compression cycle within the process that requires an external supply of gas is the nitrogen cycle. The other gases just recycle.

The quoted energy bill for a working/perfected system is only about ½ a kilowatt-hour for a liter of liquid nitrogen. ... Then again, there is the cost of the initial investment for the equipment.

Would this work: Notes on Liquifying Air

If so what compressor would I use?

rocket100 said:

Would this work: Notes on Liquifying Air

If so what compressor would I use?

Click to expand...

That looks like it might be worth a try.
The advantage would be less initial expense.
The reference book here shows that for the Linde process, you would have to have a compressor that would produce about 2940 psi gauge.
You would just about have to have a scuba tank type compressor.
A compressor used for pneumatic tools would have oil contamination, whereas a scuba tank type compressor would have purifying filtration, and no contaminants.

I would strongly recommend against trying anything like that rocket100, this is new to you and a 3000psi compressor will KILL you if something goes wrong. If I'm not mistaken you have to be licensed to even use them legally. If you wanna play, find a place where you can buy the Liquid Nitrogen in a thermos dewar. Transportation is simple you just have to vent the thermos to allow the LN2 that boils off to keep the bulk of it cool from causing the dewar to explode.

I've been curious about getting such a compressor for paintball but way too much effort.

What about a refrigerator compressor.

rocket100 said:

What about a refrigerator compressor.

Click to expand...

Not even close.

With enough stages of peltier coolers you could get the required temperatures to liquefy nitrogen out of the air using 4500 PSI scuba tanks as the air feed source.
It would be big, expensive, horribly inefficient, but just maybe cold enough to work. Maybe.

Still you would need a considerable amount of knowledge in how solid state heat pumps and high pressure air systems work to build it!

Plus the fact that you need to be 18 or older just to get the pressurized scuba tanks will still pose a problem though.

It comes down to needing lots of hands on experience and knowledge, expensive parts, special certifications, and its would still be expensive any way.

But maybe just maybe you could produce a liter or two a day for several tens of dollars worth of electricity using several thousand dollars worth or solid state components.

its probally better to forget about it. tbh your probally better off waiting till your old enough to drive then go buy a car! that way you wont need a scooter to pick chicks up in . untill then you will have to make do with going to meet them on your BMX bike

and I thought we had a Darwin award preparing there ....

Silly question, why is high pressure air needed? As long as everything is kept cold no pressure builds up.

and I thought we had a Darwin award preparing there ....

Click to expand...

I dont think he is old enough to get one of those either. He would have to be 18 or older to be legally stupid enough to get the award.

Younger than 18 just gets an 'Irresponsible parents award' for the parents from the local law enforcement and child services people. Plus some time served and lots of bad publicity!

Would this setup work, I have a de-humidifier that pulls the wetness out of the air which turns into dryair which then is fed through a insulated box with a peltier stack which then makes liquid air. If this would work what wattage would the peltiers be and how many?

Thanks everybody for replying to a curious kid .

Silly question, why is high pressure air needed? As long as everything is kept cold no pressure builds up.

Click to expand...

Yes but you can cheat on the condensing temperature by raising the pressure. If you can get to around -235 F or colder at about 500 PSI the nitrogen will condense. Then its just a matter of reducing the pressure once enough liquid is created and letting it boil off and further cool itself. It will save on a lot of additional equipment and power if you dont have to cool it all the way down with an external system. Just get it far enough to condense then let physics do the rest. Simple thermodynamics in action!

Would this setup work, I have a de-humidifier that pulls the wetness out of the air which turns into dryair which then is fed through a insulated box with a peltier stack which then makes liquid air. If this would work what wattage would the peltiers be and how many?

Click to expand...

Sort of. You would need a lot of peltier coolers set up in several layers to get it to work. Theoretically a peltier cooler will go down to absolute zero temperature wise but a single unit can only make a limited temperature differential by itself.
Plus being they have about 35% efficiency as coolers for every one on one stage there needs to be three on the stage above that. Multiply that by 8 stages (50 degrees per stage with a 400 degree temperature change) and you have a lot of individual coolers working all together to create one very large temperature differential.

stage one. 1 cooler - coldest
stage two. 3 coolers
stage three. 9 coolers
stage four. 27 coolers
stage five. 81 coolers
stage six. 243 coolers.
stage seven. 729 coolers.
stage eight. 2187 coolers. - warmest.

So as you can see their becomes a problem at some point as to realistically how many stages and how many coolers you can actually fit and power on your device.

The colder you can make your starting point and the hotter you can make your condensing point makes a huge difference in how many stages you need.

If you can start out using a good mechanical heat pump like that in an air conditioner you can get about -35 F as a reliable starting point temperature. if you can run your condensing chamber at 500 PSI you only need -235 F to get liquid nitrogen to form. Given you then only have a 200 degree temperature differential that just needs four stages of peltier coolers.
Thats realistically doable!

There are more details of course but still this gives you an idea of whats involved.

If I had a non-presserized tank how cold would it have to be for the liquid nitrogen to form?

Google nitrogen temperature and pressure curve. Then do some math. You will quickly see the problem.

-320F for Nitrogen I believe, that's it's boiling point at least. It'll vary slightly depending on your elevation

There's also the problem of removing the Oxygen, Oxygen will boil at -297F so Oxygen will liquify first, this has to be removed. Very very bad things can happen... if you get that liquid O2 near something it shouldn't be.

If I just pumped air in what would liquify first, CO2? LN2, oxygen????

search for composition of air then read up on each gas thats listed.

Nitrogen is 78% of what makes up air. Oxygen is about 21%, the next biggest component is Argon at around .9%, the rest is trace gasses so that 1% 'other' can be ignored as there's nothing consequential in it. Oxygen will condense before Nitrogen will.