There are two alternately process cycle for PSA nitrogen generator:
-Pressurisation/adsorption
-Depressurisation/desorption
Compressed air alternately pressurises each of two identical adsorber towers. Beginning at a point in the cycle where
one adsorber tower (A) is being pressurised and the other adsorber tower(B) is undergoing depressurisation, the
description of the PSA process cycle is as follows:
As compressed air enters adsorber tower A, moisture, oxygen, and carbon dioxide are adsorbed. After operating
pressure is reached, nitrogen product flows from adsorber bed A into a nitro- gen product receiver prior to entering
the product piping. Simultaneously, adsorber tower B is depressurised to atmospheric pressure.
Upon completion of nitrogen production from adsorber tower A, an equalisation step occurs. Adsorber tower B
(atmospheric pressure) is pressurised to an intermediate pressure as the gas remaining in adsorber bed A (at
operating pres- sure) flows into adsorber tower B. During this step, air is not consumed nor is product gas generated.
Therefore a nitrogen receiver is applied to allow for a constant flow, purity and pressure of the nitrogen product
throughout the PSA cycle.
Adsorber tower A then undergoes depressurisation and the oxygen enriched waste gas is vented to the atmosphere.
Depressurisation permits the release of oxygen, carbon dioxide, and water vapor previously adsorbed during nitrogen
production from adsorber tower A. At the same time, adsorber tower B is brought to opera- ting pressure, and begins
its nitrogen production portion of the cycle.
Following nitrogen production, adsorber tower B undergoes equalisation and subsequent de- pressurisation. The
cycle continues at the point where adsorber tower A undergoes pressurisation and adsorber tower B is depressurised.
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