Thread: Nitrogen extraction from air

Besides the cryogenic process of extracting nitrogen from air (in a nitrogen plant) are there any other methods of doing this. I'm not very informed about this subject. I've read something about nitrogen being extracted from air by fractional distillation - is this the same process as the cryogenic one (because it involves temperature)?

Cryogenics is the study of the production of very low temperature and the behavior of materials at those temperatures.

So yes and no. The way nitrogen behaves i take to be its properties, and so, with a boiling point of -195 - a b.p that is different from the other gases in air, you can cool them all down to their solid state, then slowly return them to room temp. And if you know the b.p of nitrogen you can release the lower b.p gases and then collect the nitrogen.

There are molecular separation methods that are not cryogenic.

Fractional distillation is one part of the cryogenic nitrogen plant. The process is energy intensive because of the large air compressor required.

Non-cryogenic methods are membrane separation and PSA (pressure swing adsorption). You can google all of these for more info.

Originally Posted by mrjoshers

Cryogenics is the study of the production of very low temperature and the behavior of materials at those temperatures.

So yes and no. The way nitrogen behaves i take to be its properties, and so, with a boiling point of -195 - a b.p that is different from the other gases in air, you can cool them all down to their solid state, then slowly return them to room temp. And if you know the b.p of nitrogen you can release the lower b.p gases and then collect the nitrogen.

Is this the actual process used for the cryogenic extraction of nitrogen from air? My understanding was it may involve cooling nitrogen and oxygen to liquid - but i'm very unclear about this!

Hey,

Well i think in a laboratory, to display the way in which such a process might work you can cool them down into solid or indeed a liquid state, and then allow the mixture to slowly return to room temperature. As the different boiling points of the elements is reached, they are released and can be collected.

Your question may be relating to an industrial level of production. The protocol and chemical engineering parts of that i do not know at all haha, im a secondary school student .

In a industrial plant id imagine a much more economical process is used for N2 extraction.

Fractional Distillation is just the manipulation of different properties chemicals possess while they are in a mixture and allows you to free them and collect them.
When doing this with air, we cool the air (a mixture of gases) down to a very low temperature. At this point the gases present in the air mixture freeze or liquify.
When we bring the temperature back up to room temperature the gases are released at different points (their boiling points) and we can collect them.

Originally Posted by wojang

Is this the actual process used for the cryogenic extraction of nitrogen from air?

No, at least not on any industrial scale.

My understanding was it may involve cooling nitrogen and oxygen to liquid - but i'm very unclear about this!

You are correct. Air (nitrogen + oxygen + argon) is compressed and cooled to the liquid state (not solid!) by Joule-Thompson expansion. The liquid is boiled in the bottom of a distillation column. The nitrogen comes off the top and the oxygen and argon come off the column at lower levels. The fractionation takes place at around -185C. This link gives a reasonably good description and process flow diagram.

http://www.uigi.com/cryodist.html

Thank you for the information and this excellent website. (Thank you both)

When the nitrogen first comes off the top, does it initially condense back into liquid before converting to a gas and leaving the distillation column?

Nitrogen leaves the top of the column as a saturated vapor carrying a relatively small amount of liquid nitrogen with it. In order to convert the nitrogen vapor to liquid you have to remove its latent heat of condensation, so it will have to go through a heat exchanger where it will exchange heat with a colder refrigerant. This means you need a refrigeration plant, so of course more energy is used.

"Besides the cryogenic process of extracting nitrogen from air (in a nitrogen plant) are there any other methods of doing this."
think this was ithe initial quest. how soon we forget.

Wiki "oxygen concentrator" its done by preferential adsorption on zeolite.
No cryogenics involved.

Originally Posted by fizzlooney

Wiki "oxygen concentrator" its done by preferential adsorption on zeolite.
No cryogenics involved.

Yep. That's how a PSA unit works.

One of the most important uses of activated carbon is removing pollutants from the water and air. It can be used in both spill cleanup and air purification of chemical plants.

http://en.wikipedia.org/wiki/Nitrogen_generator

Nitrogen Generators are readily available and are used by many Analytical labs to avoid reliance on bottled gas supplies.

how about burning away the oxygen by introducing a flame converting the O2 to CO2 and then introducing KOH/NaOH(lye) to absorb the CO2 loeaving you with only some argon and nitrogen?

Hello Help, and welcome to the forum. We generally don't think it a good idea to ressurect threads that have been inactive for more than a few months. This one was dead for almost two and a half years.

But since you have reactivated it, I'll just mention that if you are Thor you can fix the nitrogen in the soil with a well aimed lightning bolt. Or materialise as an appropriate type of bacteria.

Originally Posted by wojang

Besides the cryogenic process of extracting nitrogen from air (in a nitrogen plant) are there any other methods of doing this. I'm not very informed about this subject. I've read something about nitrogen being extracted from air by fractional distillation - is this the same process as the cryogenic one (because it involves temperature)?

I was able to separate oxygen from air in the lab by using a ceria doped samarium iron oxide (Ce0.05SmFeO30.95) fluidized bed. This is the graph I get over a few days of use. Basically, as soon as I plug in the PFR, the oxygen levels drop close to zero.