Nitrogen is obtained primarily from the air, where it makes up about 78% of Earth's atmosphere. There are a few key methods to extract and use nitrogen:
- Fractional Distillation of Liquid Air : Air is cooled until it liquefies and then separated by distillation, isolating nitrogen from other gases. This involves cooling air to very low temperatures, separating nitrogen as a liquid, and then collecting it for industrial use. This is commonly done in large-scale air separation plants.
- Nitrogen Generators : These are on-site industrial systems that separate nitrogen from compressed air using two main technologies:
- Membrane nitrogen generators , which use hollow-fiber membranes to selectively allow oxygen and other gases to permeate and retain nitrogen.
- Pressure Swing Adsorption (PSA) generators , which produce very high purity nitrogen by adsorbing other gases at high pressure and releasing them at low pressure. These methods are convenient for producing nitrogen on site with lower costs and without the need for transporting liquid nitrogen.
- Agricultural and Natural Nitrogen Fixation : Although nitrogen is abundant in the air, plants cannot directly use atmospheric nitrogen (N2) because of its strong triple bond. Instead, certain bacteria in soil or in symbiosis with plant roots fix nitrogen by converting N2 into ammonia or other compounds plants can absorb. This process, called nitrogen fixation, is crucial for plant nutrition but differs from industrial nitrogen extraction.
In summary, industrially, nitrogen is obtained by separating it from air either by fractional distillation or nitrogen generators. In nature, nitrogen is made accessible to plants mainly through biological nitrogen fixation by microorganisms.
