Pressure Swing Adsorption (PSA) Technology

pressure swing adsorption work?

When you produce nitrogen yourself, it is important to know and understand the purity level you want to achieve. Some applications require low purity (90% to 99%), such as tire inflation and fire prevention, while others, such as the food and beverage industry or plastic molding, require high purity (97% to 99.999%). In these cases, PSA technology is the ideal and simplest method.

In fact, the working principle of the nitrogen generator is to separate the nitrogen molecules from the oxygen molecules in the compressed air. Pressure swing adsorption achieves this by using adsorption to capture oxygen from a compressed air stream. Adsorption occurs when the molecules are combined with the adsorbent. In this case, the oxygen molecules are attached to the carbon molecular sieve (CMS). This occurs in two separate pressure vessels, each equipped with CMS, switching between the separation process and the regeneration process. For now, let's call it Tower A and Tower B.

First, clean and dry compressed air enters Tower A. Since oxygen molecules are smaller than nitrogen molecules, they will enter the pores of the carbon sieve. On the other hand, nitrogen molecules cannot enter the pores, so they will bypass the carbon molecular sieve. As a result, the required purity of nitrogen was finally obtained. This stage is called the adsorption or separation stage.

, however, it did not stop there. Most of the nitrogen produced in tower A exits the system (ready for direct use or storage), while a small part of the nitrogen produced flows into tower B in the opposite direction (from top to bottom). This gas stream is required to push out the oxygen trapped in the previous adsorption phase of Tower B. By releasing the pressure in tower B, the carbon molecular sieve loses its ability to contain oxygen molecules. They will be separated from the sieve and carried away through the exhaust through a small nitrogen stream from tower A. By doing so, the system makes room for new oxygen molecules to attach to the sieve in the next adsorption stage. We call this "cleaning" process saturated oxygen tower regeneration.

First, tank A is in the adsorption stage, while tank B is regenerated. In the second stage, both containers should equalize the pressure and be prepared for switching. After switching, tank A starts regeneration, while tank B generates nitrogen.

at this point, the pressure in the two towers will be equal, and they will change from the adsorption stage to the regeneration stage, and vice versa. The CMS in tower A will reach saturation, while tower B will be able to restart the adsorption process due to decompression. This process is also called "pressure fluctuation", which means that it allows certain gases to be captured at higher pressures and released at lower pressures. The twin-tower PSA system allows continuous production of nitrogen at the desired purity level.