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In
order to produce nitrogen, the generator requires compressed air.
Atmospheric air contains roughly 78% nitrogen, 21% oxygen, 0.9% argon and
the balance is other gasses. The compressed air which
reaches the nitrogen generator has the same composition. To produce a
specific gas, the generator needs to separate the required gas molecules in
the compressed air, and two different technologies of separation are used
to produce nitrogen: PSA (Pressure Swing Adsorption) and membrane
technology.
PSA is a filtration technology, which utilizes carbon molecular sieve (CMS)
to separate the nitrogen from the other gasses. The PSA system normally
contains two beds of CMS, which simultaneously either receives compressed
air or leads the adsorbed gasses out of the PSA-beds.
Membrane technology is based on a bundle of small individual hollow fibres.
Each fibre has circular cross-sections and a uniform bore through its
center. When the compressed air under high pressure enters the surface
area, the gasses inside the air are divided up and forced into each fibre.
Oxygen and water vapour are considered gasses, which quickly run through
the fibres and even permeate the membranes. This allows the final gas -
nitrogen - to flow through the fibre bores as the product steam.
Due to the small size of the fibres, a high number may be placed into a limited
space and provide an extremely large membrane surface area, allowing for a
high nitrogen output.
In comparison, the membrane system requires higher airflow than PSA in
order to produce the equivalent amount of nitrogen.
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