Atmospheric air consists of approximately 78.1 % nitrogen, 20.8 % oxygen, 0.9 % argon, and about 0.2 % of other noble gases. Gaseous nitrogen is widely used in processes that require an inert environment. There are several ways to supply nitrogen to a production site: delivery in high-pressure cylinders or as liquid nitrogen, or on-site generation using membrane systems, cryogenic plants, or PSA (Pressure Swing Adsorption) units.
Cryogenic air separation systems extract nitrogen through low-temperature fractional distillation. While efficient at producing high-purity nitrogen in large volumes, these systems are complex to operate and require highly qualified personnel. They are typically suited for large-scale industrial facilities.
In the past two decades, PSA nitrogen generators have gained popularity as a cost-effective and efficient solution for producing gaseous nitrogen. These systems are simpler, more mobile, and easier to operate, making them ideal for small to medium-sized enterprises. Key advantages include quick start-up times, minimal maintenance, and flexible purity control.
How PSA Nitrogen Generators Work
PSA systems operate based on the different physical properties of gas molecules — particularly their size and structure. For instance, nitrogen molecules (~0.39 nm) are slightly larger than oxygen molecules (~0.32 nm). By using a porous material such as carbon molecular sieve with a pore size of ~0.40 nm, oxygen molecules are preferentially adsorbed into the material while nitrogen passes through.
By regulating the flow rate and cycle timing, PSA generators can consistently produce nitrogen of the desired purity. Modern PSA systems typically follow a dual-bed configuration first proposed by Skarstrom in 1960. Since then, the technology has been continually refined, with particular focus on selecting efficient adsorbents, improving packing density, ensuring even flow distribution, and optimising cycle parameters for better energy performance.
Energy Efficiency and Operating Principle
PSA nitrogen generators are energy-efficient, with specific energy consumption as low as 0.19 kWh per 1 m³ of nitrogen, depending on the unit’s capacity and required purity. The process operates at moderate pressures, typically not exceeding 10 bar(g).
Here’s a simplified overview of the PSA cycle:
- Compressed and pre-treated air (filtered from dust and moisture) enters the adsorption column from below.
- As air flows through the molecular sieve, oxygen and other trace gases are adsorbed, while nitrogen moves toward the outlet.
- A portion of the nitrogen is used to regenerate the second column.
- Once the cycle completes, pressures are equalised and the system switches to the regenerated column.
- Each half-cycle typically lasts 45–90 seconds, depending on system parameters.
The nitrogen product is collected in a buffer tank (receiver), which smooths out fluctuations in flow. Its size depends on system output and column volume. After buffering, nitrogen is delivered to the end user via flow, pressure, and purity monitoring systems. Standard delivery pressure is 8 bar, though systems can be customised to specific requirements.
Advantages of PSA Nitrogen Generators Over Alternative Methods
-
Low Cost of Production
On-site nitrogen production is significantly more cost-effective than purchasing bottled or liquid nitrogen. At an electricity cost of 4 RUB/kWh, the cost per m³ of nitrogen (at 97 % purity) is around 0.76 RUB/m³.
-
Compact Design
PSA units have a small footprint, making them ideal for space-limited sites.
-
Flexible Purity Control
Nitrogen purity can range from 95 % to 99.9995 %, depending on application needs.
-
Fully Automated Operation
PSA systems are easy to operate, with minimal human involvement required.
-
Quick Installation and Commissioning
Units can be delivered, installed, and commissioned rapidly.
-
Operational Safety
PSA systems are inherently safe for on-site nitrogen generation.
These benefits make PSA nitrogen systems a preferred solution for mid-range industrial gas needs. They offer enterprises energy efficiency, autonomy, and significant cost savings.
Our Offering
ONH Systems supplies both standard PSA nitrogen generators and tailored engineering solutions for a wide range of production capacities. All systems are designed and manufactured in Russia to meet both domestic and international standards.
If you have any questions or require assistance in choosing the right nitrogen generation system, our specialists are ready to provide expert support.
