What is a PSA Nitrogen Generator?

How a PSA Nitrogen Generator works.

In a PSA nitrogen generator or Pressure Swing Adsorption nitrogen generator the adsorption technology is a physical separation process, which uses the different adsorption affinities of gases to a microporous solid substance, the so-called adsorbent. Oxygen, for example, has a higher adsorption capacity to some carbon molecular sieves than does nitrogen. This characteristic is used with the Pressure Swing Adsorption (PSA) plant for the generation of nitrogen. The main advantages of this process are the ambient working temperature, which results in low stresses to equipment and adsorbent material and the low specific power consumption.

The PSA-Nitrogen Generator plant consists of the main equipment: air compressor, refrigerant dryer, air receiver tank, 2 adsorber vessels filled with adsorbent material and a product buffer. Each adsorber operates on an alternating cycle of adsorption and regeneration, thus always a continuous nitrogen product flow is achieved.

The PSA-Nitrogen Generator Plant works according to the following process steps:

Adsorption
Compressed and dried air at ambient temperature is heated and fed into the Pressure-Swing-Adsorption (PSA)-vessel (adsorber) at the compressor discharge pressure. The adsorber is filled with molecular sieves. The remaining moisture and carbon dioxide in the air are removed at lower layers of the bed, oxygen is adsorbed by the upper molecular sieve filling. The remaining, nitrogen-rich product gas leaves the adsorber at the outlet and is fed to the nitrogen buffer. Before the adsorption capacity for oxygen is depleted, the adsorption process is interrupted so that no oxygen can break through at the adsorber outlet.

Regeneration\Purge
The saturated adsorber is regenerated by means of depressurization and additionally by purging with nitrogen produced by the second adsorber in order to remove the adsorbed gases H2O, CO2 and O2 from the adsorbent bed. The waste gas is vented to the atmosphere.

Repressurization
Afterwards regeneration the adsorber is refilled with air and part of the recycled nitrogen. The adsorber is then ready for the next adsorption step.