How nitrogen gas is made

Industrial nitrogen is simply air, chilled until it liquefies and then boiled apart again.

stations: 5
things upstream: 1
raw source: 1
step from the ground: 1

The short version

Nitrogen gas is separated from air by cooling air until it turns to liquid, then distilling it. Nitrogen boils at a lower temperature than oxygen, so it rises as a vapor out of the top of a tall column while oxygen collects at the bottom. Small sites often use membranes or pressure-swing beds instead.

Suck in and compress air

Big compressors draw in outside air and squeeze it, and the compression is the energy source for the whole plant. The water that condenses on the way is drained off.

Goes in
Air
Strip out water and CO2

The air passes through beds of molecular sieve that trap remaining moisture and carbon dioxide. Left in, these would freeze solid and plug the frigid equipment.
Chill it near liquefaction

In a plate-fin heat exchanger the incoming air is cooled against the cold product streams leaving the plant. Part of the air condenses to a liquid with extra oxygen in it.
Boil it apart in a column

Nitrogen boils at a lower temperature than oxygen, so it rises as vapor through the column while oxygen-rich liquid trickles down. The nitrogen at the top can reach better than one part per million of impurity.
Store as liquid or pipe as gas

Nitrogen is shipped as a liquid in insulated tankers or piped to nearby factories as a gas. The cold equipment sits inside an insulated enclosure called a cold box.

End of the lineNitrogen gas Next it goes into polysilicon, memory chip, window glass and 5 more.

Worth repeating

Nitrogen makes up about 78% of Earth's atmosphere, which makes it the most common chemical species in the air.
Carl von Linde developed air liquefaction in 1895, and it was first used in industry in 1902.
Pressure-swing and membrane systems can pull one gas from ordinary air, but the highest-purity nitrogen and oxygen still require cryogenic distillation.