PSA (Pressure Swing Adsorption) is a technology commonly used in gas separation and purification processes such as oxygen and nitrogen production. In the oxygen production process, PSA is the method used to separate oxygen and nitrogen in the air.

The PSA system works as follows:

1. Compressed air feed: The air is compressed by the compressor and reaches the required working pressure.

2. Adsorbent bed: Compressed air passes through an adsorbent bed and is adsorbed on the adsorbent (usually a molecular sieve) in the adsorbent bed.

3. Adsorption stage: In the adsorption stage, inert gases such as nitrogen are captured by the adsorbent, while active gases such as oxygen flow through the adsorbent bed.

4. Desorption stage: When the adsorbent bed is saturated, it needs to be regenerated, which is the desorption stage. At this point, the pressure in the adsorbent bed is reduced, usually by releasing the gas, to reduce the gas concentration on the adsorbent. 

5. Emission of waste gas: During the desorption stage, the adsorbent bed releases the adsorbed gas to form waste gas, which is usually discharged into the atmosphere.

6. Switching adsorption beds: When one adsorbent bed is saturated, the PSA system will automatically switch to another adsorption bed for adsorption, while the currently saturated adsorption bed will be regenerated to achieve continuous oxygen production.

By repeatedly performing adsorption and desorption stages, the PSA system is able to separate nitrogen and other impurity gases in the air from oxygen to achieve high-purity oxygen production. This technology is widely used in medical, industrial and other fields where pure oxygen is required.