PSA technology relies on a process called adsorption, which is the tendency of gases to be drawn to solid surfaces when subjected to high pressure. Different surfaces attract different gases more strongly, meaning target-rich gases can be attained by selecting the most suitable material.
A nitrogen-rich supply could, for example, be achieved by passing a gas mixture such as air under pressure through a unit employing an adsorbent foundation of zeolite that attracts nitrogen more strongly than oxygen. The target gas, in this case nitrogen, will remain held in the bed, with the vented gas being subsequently enriched in oxygen. When the bed is full, the absorbed nitrogen can be released in a controlled manner by easing the pressure, thus allowing the gas to be regenerated and a new cycle to begin.
Exercising two adsorbent vessels warrants almost permanent production of the target gas.
Whilst the capability to distinguish between different gases is clearly the most fundamental factor in the selection process, the materials used for adsorbents are also identified for being highly porous and having a large surface area.
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