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How to Make Liquid Nitrogen Through Distillation

Liquid nitrogen is used in industrial and research applications. Providing the product to customers isn't difficult, as its availability is abundant. The generation of liquid nitrogen for commercial purposes comes from liquid air. The three components of liquid air are nitrogen, oxygen and argon. Other trace gases are present. Purification separates the major components from the trace gases. The purification of liquid nitrogen occurs through fractional distillation from liquid air. The boiling point of nitrogen is -320 degrees Fahrenheit, significantly different from the boiling point of the other components of liquid air.

Things You'll Need

Cryo-cooler
Fractional distillation column, high pressure
Fractional distillation column, low pressure
Sub-cooler
Compressor
Vacuum storage tank

Instructions

- 1
  Enclose the entire apparatus in a cryogenically-cooled environment. Most applications use jacketed pipe that recirculates the refrigerant through the system. All surfaces are temperature controlled by the refrigerant. Most plants producing liquid nitrogen and oxygen use the cooled gases obtained through an expansion valve to cool the remainder of the system. The air stream cools as it enters the cryogenic portion of the plant.
- 2
  Direct the flow of air into the bottom of a high pressure fractionating column. As the air cools, liquid oxygen starts to form due to having the highest boiling point. The liquefied oxygen remains at the bottom of the column as the argon and nitrogen flow to the top. Both gases lose more heat until argon and nitrogen pass through the top of the column into a sub-cooler.
- 3
  Direct the air flow from the sub-cooler into the bottom of a low pressure fractionating column where the argon liquefies and collects in the bottom of the column. As the nitrogen flows out of the top of the column, it's directed into a compressor to liquefy the nitrogen and store it in a vacuum storage vessel.
- 4
  Seal the collection vessel under pressure to maintain the nitrogen in liquid form.

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