Pressure swing adsorption

Pressure swing adsorption (PSA) is a technology used to separate some gas species from a mixture of gases under pressure according to the species' molecular characteristics and affinity for an adsorbent material. It operates at near-ambient temperatures and differs significantly from cryogenic distillation techniques of gas separation. Specific adsorbent materials (e.g., zeolites, activated carbon, molecular sieves, etc.) are used as a trap, preferentially adsorbing the target gas species at high pressure. The process then swings to low pressure to desorb the adsorbed material.

Process

Pressure swing adsorption involves a sequence of steps as follows: pressurization, production, depressurization and purge. The gas mixture to be separated is fed into the adsorption vessel at high pressure, where the adsorbent material selectively adsorbs the desired gas components. The remaining unadsorbed gases are vented out of the vessel. The pressure is then reduced, releasing the adsorbed gases, which are then purged from the system.

Applications

PSA technology can be used to separate gases in a mixture because different gases tend to be attracted to different solid surfaces, or "adsorbents". PSA processes can be used in gas purification, gas drying, hydrogen purification, carbon dioxide removal and is widely applied in industries such as chemical, petrochemical, and energy.

Advantages and Disadvantages

The main advantage of PSA technology is its ability to produce high purity gases at relatively low cost, especially when the desired product gas constitutes a significant fraction of the feed gas mixture. However, the technology is generally not suitable for the separation of gas mixtures where the concentration of the desired product is low.

See Also

• Adsorption
• Gas separation
• Cryogenic distillation

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