How is liquid nitrogen separated from air by fractional distillation?

Commercial production of nitrogen is primarily achieved through the fractional distillation of liquefied air.1

This process relies on the difference in boiling points between the components of air. Nitrogen has a boiling point of −195.8 °C (−320.4 °F), which is approximately 13 °C (23 °F) lower than that of oxygen. Because nitrogen is more volatile, it vaporizes and can be separated from the liquid mixture, while the oxygen is left behind.12

In industrial fractional distillation, the process is enhanced by using a fractionating column where vapours are repeatedly condensed and revaporized. This setup ensures close contact between rising vapour and descending liquid, allowing the more volatile nitrogen to proceed as vapour to the receiver while the less volatile components are returned to the still as liquid.2