Nitrogen and Oxygen Production with Membranes

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Nitrogen Generation with Membrane Technology

Membrane Module Arrangement

Membrane nitrogen generators are equipped with tubular modules which are filled with a bundle of small diameter polymeric hollow fibres, arranged similar to the internal design of shell and tube heat exchangers.

The modules are typically installed in parallel and supplied with clean and dry compressed air to the inlet of the module housing where the air is fed to one end of the fibres and separated into a nitrogen enriched and an oxygen enriched stream.

Membrane Air Separation Principle

Air separation with membranes is based on the different permeation rates of the gases in air through the polymer surface of the membrane fibres.

Oxygen (O2), water vapour (H2O) and carbon dioxide (CO2) are able to move faster through the membrane tube walls than argon (Ar) and nitrogen (N2). The less diffusible gases nitrogen and argon remain longer in the fibre tubes and thus can be concentrated as nitrogen product gas while the fast gases are vented as waste gas named permeate from the shell to the environment with no backpressure.

Membrane Performance and Properties

Using this technology dry compressed air with up to 20 bar g can be converted to a gaseous product that consists of 95 ... 99,5 % Vol. nitrogen gas including little argon while the nitrogen product pressure level is approx. 1 bar g less than the inlet pressure.

The remaining oxygen content in the nitrogen gas is adjusted by using a manual or PLC operated flow control valve at the outlet of the membrane module set.

Membranes produce very dry nitrogen quality of approx. -40° C atmospheric dew point respectively -20° C pressure dew point at a pressure of 7 bar g.

The membranes act like a filter with no moving parts and continuously generate nitrogen at the selected flow and purity.

Oxygen Generation with Membrane Technology

The vented gas stream named permeate is including nearly the complete oxygen when the flow control valve is closed to a minimum. So the oxygen content in the permeate can rise up to 40 % Vol. O2. This oxygen enriched air can be compressed for further use. The oxygen content can not be increased like with PSA generators who generate up to 95 % Vol. oxygen.


Membrane Gas Permeation Simplified Schematic