You will recall that about 78 percent of the air is nitrogen and 21 percent is oxygen. These two gases can be separated by fractional distillation of liquid air.
Liquefying the air
Air is filtered to remove dust, and then cooled in stages until it reaches –200°C. At this temperature it is a liquid. We say that the air has been liquefied.
Here's what happens as the air liquefies
· water vapour condenses, and is removed using absorbent filters
· carbon dioxide freezes at –79ºC, and is removed
· oxygen liquefies at –183ºC
· nitrogen liquefies at –196ºC.
The liquid nitrogen and oxygen are then separated by fractional distillation.
Comments
No comments have yet been made