How does pressure swing adsorption work in compressed air systems and nitrogen generators?

Compressed air systems and nitrogen generators may be two different types of equipment, but they do have one thing in common which is that they both function via the principal of pressure swing adsorption.

In this article we’ll go over the basics of how pressure swing adsorption works, the differences to be aware of when it comes to its application in air compressors and nitrogen generators and how it helps your equipment run as efficiently as possible.

What is pressure swing adsorption?

Pressure swing adsorption is a process that is used to separate single gases from a mixture of gases under pressure for the purposes of purification. It is usually air that is purified, but in the case of this article we will also be talking about how pressure swing adsorption can help with the purification of nitrogen.

How does pressure swing adsorption work?

Before we get into how pressure swing adsorption works, it’s important to know the difference between adsorption and absorption. Whereas adsorption involves molecules adhering to the surface of a material, absorption involves one substance entering into the bulk of another.

PSA Nitrogen Generators

PSA nitrogen generators are used widely across multiple industrial facilities because the adsorption process is one of the most efficient ways of recovering high-purity nitrogen.

As air enters the generator, the O2, molecules adhere to the surface of the adsorbent material. The adsorbent material is primarily a carbon molecular sieve that is designed to capture oxygen molecules and let nitrogen molecules pass through.

Once the carbon molecular sieve (CMS) becomes saturated with oxygen molecules, the generator system switches to the second tower which then begins adsorbing as the former CMS tower begins depressurization in order to release O2 and other trace gases back into the atmosphere; the system alternates between the two towers to ensure a continuous flow of nitrogen production

PSA  Compressed Air Drying

Pressure swing adsorption works in conjunction with air compressors to help to separate and purify gases from compressed air.

The air compressor takes in ambient air and compresses it to a high pressure, but before it can reach the adsorbent material, filters remove oil and dust from the compressed air and an air dryer removes traces of water vapour. It is vital that the compressed air is free from contaminants before entering the PSA unit to prevent the adsorbent material from getting damaged.

Much like PSA nitrogen generators, there are two towers in the case of air compressors they are both filled with a desiccant media such as silica gel, molecular sieve or activated aluminum, the choice being based around the desired air quality outcome or performance expectations for the application. The two towers alternate adsorption and depressurization roles to allow for the continuous production of purified nitrogen or oxygen.

What are the advantages of using pressure swing adsorption?

There are several benefits to relying on PSA systems for the purification of gas for industrial applications, such as:

• Quality of gas – for example, nitrogen gas with upto 99.9995% purification can be produced with the help pressure swing adsorption
• Reliability – pressure swing adsorption works on a cycle of continuity involving the two towers and so an uninterrupted flow of gas can be provided
• Flexibility of gas supply – the production of nitrogen/oxygen gas can be altered according to changes in demand with minimal hassle

Different types of PSA technology

In this article we have been focusing on the functionality of Two-Bed PSA as this is the best to use for industrial nitrogen and oxygen generation systems. There are other variants of PSA technology that are available for different purposes, such as:

• Single-Bed PSA – used for low-duty applications and experimental setups
• Multi-bed PSA – used for high-volume operations
• Rapid PSA – used for portable or compact gas generators
• Vacuum PSA – used for applications requiring high-purity oxygen such as medical and steel industries
• Temperature Swing Adsorption – this can be used as alternative to or in tandem with PSA and is best for removing moisture and volatile organic compounds.

If you are interested in hiring or purchasing a PSA air compressor or nitrogen generator and would like to talk in more detail, you can leave us a message on our contact page or alternatively get in touch with us at enquiries@maziak.co.uk or on 01933 222000.