PSA or Membrane Generator: Which One Is Right for Your Application?

Feb 06, 2020

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PSA or membrane generator

Nitrogen generation provides a clean, environmentally friendly and cost-effective nitrogen source for many industrial applications. In almost every case, having on-site nitrogen generation is more economical, convenient and sustainable than purchasing liquid nitrogen from a supplier. Pressure swing adsorption (PSA) and hollow-fiber membrane are two popular types of nitrogen generators, each suited for a particular application.

Factors such as the amount of nitrogen required, nitrogen purity, adverse environmental site conditions or the desire to scale nitrogen production in the future effect which system is best for you, but, whatever your needs, Fluid-Aire Dynamics has an industrial nitrogen generator system that will meet your demands.

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What Is a Pressure Swing Adsorption Generator and How Does It Work?

When an industrial application requires the highest-purity nitrogen gas (~99.9995%), such as in analytical chemistry, chemical and petroleum, metallurgy or electronics manufacturing, a pressure swing adsorption nitrogen generator is most commonly used.

The PSA generator works by pulling air into a tank containing a material called a carbon molecular sieve (CMS). Pressure then increases in the tank, and as air passes over the CMS material, oxygen and other undesirable particles are absorbed into it, allowing the nitrogen to pass through and exit into a collection tank. Once the CMS material becomes saturated with oxygen and particulates, the pressure in the tank is lowered, and a high-purity stream of nitrogen gas cleans out the CMS material, preparing it for another cycle.

Due to the cyclic nature of this process, two cylindrical tanks, often called adsorbent columns, are used in tandem. Each tank alternates between generating high-purity nitrogen and cleaning the CMS material every 60 seconds. To keep the CMS material operating with high efficiency, the incoming air stream must be dehumidified. This is accomplished by a refrigeration system. Because the PSA process uses two adsorbent columns, a buffer tank is required to collect the nitrogen gas from each tank. This buffer tank keeps the pressures of the two adsorbent columns similar and ensures that a high-purity concentration of nitrogen gas is produced from both tanks. To cycle between the two adsorbent columns, a control module is used with multiple valves and sensors.

Compared to other types of gas generators, the PSA generator is specifically designed to filter out nitrogen as opposed to oxygen, which is ideal for high-volume or high-purity applications. The PSA can be used in various industries, including the electronics, pharmaceutical and metal fabrication industries. One of the reasons that the PSA generator is a popular choice among these industries is that it can produce the highest purity of nitrogen gas than other generators, including a membrane generator. Additional benefits from using a PSA generator over a membrane generator include:
  • Reliability: If a PSA generator is properly maintained, it can last for years. A well-maintained PSA system can last upwards of 20 years with the right care.
  • Low maintenance requirements: In general, PSA generators only require annual filter cartage changes. The pellets that make up the CMS material are designed to last for years, meaning they won't need to be repaired or replaced for decades.
  • Consistency: Some people worry that as the years pass, a PSA generator won't be able to produce the same volume of nitrogen as it would when it was first purchased. However, PSA generators can produce a high volume of nitrogen for as long as the system remains operational.

how does a membrane generator work

What Is a Membrane Generator and How Does It Work?

A membrane nitrogen generator works by using a polymer membrane material to passively separate nitrogen gas, often with a purity range of 95 to 99.9%. The membrane generator works by allowing some gas molecules, such as oxygen, water vapor and other particulates fast passage through its walls while restricting the flow of nitrogen gas.

As air enters the cylindrical tube containing the membrane module, the unwanted gases, vapors and contaminants pass through the membrane and are quickly directed to an exhaust vent. The slower-moving nitrogen gas travels through the membrane, bypassing these premature exit routes and discharging at the outlet of the tube.

Because of the continuous flowing nature of the membrane nitrogen generator, the process can operate indefinitely, producing a continuous flow of nitrogen gas. This process also contains no moving parts, which is ideal for environments prone to excessive vibration or shock or for applications where low maintenance requirements are desirable. In addition, the polymer membrane material does not require the incoming airflow to be free from water vapor, unlike the PSA system — eliminating the need for a compressed air drying system.

Due to the simple process of the membrane generator nitrogen production, membrane generators can be installed in a modular fashion, allowing a facility to easily scale up or down its nitrogen gas production.


Compared to the PSA generator, a membrane generator is better suited to other industries, such as food and beverage, aerospace and automotive industries. Membrane generators produce a lower purity of nitrogen when directly compared to a PSA generator, making them the ideal choice for these industries. However, there are some benefits of choosing a membrane generator over a PSA generator, including:
  • Simple designs: As stated above, the process used to produce a continuous flow of nitrogen requires no moving parts. Membrane generators can be customized for their configuration and mobility, which other generators aren't always capable of.
  • Compact and quiet: One of the reasons some industries choose membrane generators over PSA generators is their ability to run quietly and take up little space.
  • Reliability: One of the main benefits of a membrane generator is that they have very few moving parts, if any at all. When the generator is maintained correctly, it can last decades without extensive maintenance. At most, the filter cartridges will need replaced once a year.

Choosing the right generator will depend on the needs of your industry. Neither a PSA nor membrane generator is a one-size-fits-all system. You'll need to consider the variables, such as pressure, flow rate and nitrogen purity and which system would be the proper choice for your requirements.

benefits of choosing a membrane generator over a PSA generator

Benefits of Using a Nitrogen Generator for On-Site Nitrogen Generation

For industries requiring nitrogen gas in their manufacturing or other operational procedures, there are key advantages of on-site nitrogen production and supply that can improve overall business operations. Additionally, having a continuous supply of high-purity nitrogen provides other benefits, including for health and safety and the environment when delivered via a PSA or membrane nitrogen generation system. Below are some of the important benefits of industrial nitrogen generator systems to consider for your business practices.

1. Low Operating Cost

If your process requires a consistent supply of nitrogen gas, chances are that a liquified nitrogen gas distributor will deliver tanks of nitrogen gas to your facility. The problem with purchasing gas this way is the high cost to both your business and the environment.

Purchasing nitrogen gas through a distributor can include unforeseen costs such as tank rental fees, delivery charges and hazmat fees — not to mention the negative environmental effects produced by the vehicles delivering bottles to your facility. Another consideration is the facilities and associated floor space required to store tanks of nitrogen. These spaces often require additional fire protection consideration, and in some cases, local authorities will require retrofitted or upgraded fire suppression systems, which carry considerable costs.

Depending on geographical location and other factors, the delivery of cylinders of nitrogen gas can cost several dollars per 100 cubic feet. Using a membrane or PSA nitrogen generator can drop the cost of nitrogen gas to nearly 20 cents per 100 cubic feet in some cases, regardless of site location. Although there is an initial capital cost of purchasing and installing an on-site nitrogen generation system, you can expect a payback period of only nine to 24 months. After this payback period, nitrogen generation costs can be cut in half, which consists of only maintenance and energy costs.

2. Safe and Stable

When nitrogen gas is produced for distribution in pressurized tanks, it requires a liquefaction process. This consists of lowering nitrogen gas temperature to -320°F for it to become a liquid. These highly pressurized tanks containing extremely cold nitrogen pose certain safety risks to the workers handling them. If handled improperly or exposed to excessive heat, tanks of liquid nitrogen can explode, seriously injuring or even killing workers. As a result, many safety precautions must be taken, which costs additional time and money to develop and implement.

Safety concerns and associated additional costs are entirely eliminated by using an on-site membrane or PSA nitrogen generator. Neither of these processes requires the nitrogen to be chilled or pressurized to a dangerous degree. The chemically inert nature of nitrogen gas means that it’s not flammable or reactive with virtually any compounds or elements it might come in contact with, making it safe for workers to handle and interact with.

on-demand nitrogen generation systems

3. Convenient and On-Demand

In this age of efficient and streamlined manufacturing, customer expectations have never been higher. They want their products, materials or services to be efficient, cost-effective and of the highest quality. This means every material used in the production must be available and on-demand at all times. Having a membrane or PSA nitrogen generator on-site means never having to wait for a supplier to deliver their product to your door. On-site generators eliminate logistic resources that could be used in other areas of your operation to improve processes and reduce the chance of production bottlenecks.

Having a membrane or PSA nitrogen generator on-site allows you the freedom to stockpile nitrogen during times of low demand. This enables flexibility in manufacturing operations, which doesn’t require you to rely on a nitrogen supplier and their production and delivery schedule.

Membrane nitrogen generators also have the unique flexibility to be installed in a modular arrangement with other membrane generators, allowing you to scale up or down production depending on your needs.

4. Environmentally Friendly

The environmental impact of manufacturing processes is of primary concern in this age of climate change. Reducing CO2 and other greenhouse gas emissions aids in reducing the harmful effects of industry on the planet and also ensures processes are sustainable long into the future.

Using a membrane or PSA nitrogen generator removes the need for many processes that contribute to the generation of greenhouse gases. When nitrogen gas manufacturers produce nitrogen gas to bottle for transportation and distribution, it must first be chilled to -320°F. This requires an immense amount of electrical energy, which results in the emission of harmful greenhouse gases, not to mention high costs that are ultimately passed on to you. After the nitrogen gas is liquified and bottled, it’s transported by truck to your facility, which incurs additional negative greenhouse gas emissions and transportation costs.

By choosing to forgo bottled nitrogen gas, you are choosing to reduce the negative effects of outdated industrial practices that are no longer required. Your customers will also appreciate the use of this green technology when performing their product life cycle analysis and be more likely to purchase your products or services due to their lower carbon footprint.

what are nitrogen generators used for

What Are Nitrogen Generators Used For?

Nitrogen gas is one of the most popular gases used in industrial and commercial processes and for good reason. It’s used in metallurgical processes, fertilizer manufacturing and even in the production of explosives.

Nitrogen gas is also used to prevent oxidation from eroding materials and decaying food products. Oxidation is a naturally occurring phenomenon in which oxygen molecules in the air react with common materials, slowly degrading them. This poses a huge problem for the industry. It’s estimated to cost globally $2.5 trillion or 3.4% of the global gross domestic product (GDP) to combat the effects of corrosion annually. Nitrogen is often used to displace atmospheric air and shield materials from the harmful effects of oxidation.

Because of its versatility and practical applications, nitrogen generators are used in important industrial settings, including the following processes and functions.

1. Fire Protection Systems

Nitrogen has multiple uses in fire protection systems. Dry fire protection systems are used in locations where water-filled pipes are in danger of freezing. They work by filling the pipes with a gas, and when a sprinkler head is activated, the system then fills with water to extinguish the fire. Problems with corrosion can arise in these dry systems when the compressed air used to fill the pipes contains too much moisture and begins corroding the pipes, fittings and even the sprinkler heads themselves. To prevent this, nitrogen gas is used as a fire sprinkler corrosion prevention system, as it has a non-reactive relationship with the metallic or plastic sprinkler pipe or component materials.

In locations where fire suppression systems are required but are sensitive to water damage, such as server rooms or electrical rooms, nitrogen systems are commonly used. Nitrogen systems work by displacing the oxygen-rich atmospheric air, leaving the fire with not enough oxygen to continue to burn, putting it out very quickly. These nitrogen fire protection systems require a room to be fairly airtight so that the nitrogen gas can sufficiently lower the concentration of oxygen in the room.

2. Food Transportation and Packaging

Similar to material oxidation, food products undergo a similar decaying process when exposed to atmospheric oxygen. Many biological processes that accelerate the decay of food products are also accelerated in an oxygen-rich environment.

To combat oxidation and preserve food freshness, food products are kept in a nitrogen-rich environment. This allows food products, including fruits and vegetables, to be grown and harvested far from where they are ultimately sold and consumed. Many regions around the world rely solely on agriculture for their survival and prosperity, and nitrogen gas makes this possible.

3. Metallurgical Processes

Nitrogen gas is used in a wide variety of ferrous and nonferrous metal manufacturing processes. From casting to annealing to brazing and hardening, nitrogen gas is used to provide a buffer between the material and oxygen contained in the atmospheric air. During casting, annealing and tempering processes, ferrous metals are heated to different temperatures to achieve a desirable molecular arrangement within the material and to relieve stress. One unwanted side effect of heating ferrous metals to these temperatures is that it makes the metal susceptible to surface oxidation.

Oxygen molecules can react more easily with the surface of the metal and create unwanted by-products, such as rust. Nitrogen is used to displace the oxygen around the material long enough for it to cool down to a temperature where it is less susceptible to oxidation.

Welding and cutting processes such as plasma cutting and shield-metal arc welding often use nitrogen gas to prevent a phenomenon known as hydrogen embrittlement. Hydrogen embrittlement occurs when atmospheric air comes in contact with a ferrous material that’s undergoing a cutting or welding process.

Hydrogen atoms in the air become trapped inside the welded joint and lead to extremely brittle material properties, making a much weaker product. Nitrogen is used as a buffer to prevent atmospheric hydrogen from coming in contact with the weld or cutting site, preventing hydrogen embrittlement.

4. Aircraft and Motor Vehicle Tires

One major advantage of using compressed nitrogen rather than compressed air to fill tires is that nitrogen maintains a much more consistent pressure when heated and cooled compared to air. This is extremely important when tires are subjected to a wide range of temperatures, such as on an aircraft or race car.

The suspension systems in these vehicles require a consistent volume and mechanical behavior to ensure safety and performance. Another advantage of using nitrogen as a compressed gas instead of air is that the natural moisture in the air begins to precipitate out when it’s compressed sufficiently.  This water content then makes its way into tires and can begin to corrode the wheels, leading to mechanical failure.

5. Petroleum, Electronic and Pharmaceutical Industries

In many petroleum production processes, nitrogen gas is used to create an inert environment to prevent explosions, as well as disperse fine, airborne particulates. Nitrogen is also used during the manufacturing of electronic components. Semi-conductors and electrical circuits often require oxidation protection while heat-treating and a particulate- and water-vapor-free gas to blow off and clean components after manufacturing.

The pharmaceutical industry also uses nitrogen gas in a similar capacity to the petroleum industry. They use it to displace fine flammable particulates to prevent explosion and contamination.

6. Paint, Varnish and Glass Industries

Paint and varnish production is a chemical process requiring an inert, oxygen-free environment to prevent the polymerization of drying oils. During glass production, electric arc furnaces are used. The electrodes in electric arc furnaces used to conduct the electricity require cooling and are susceptible to oxidation similar to other ferrous and nonferrous metals when heated to high temperatures. As a solution, nitrogen gas is used as a cooling fluid.

psa or membrane generator

Choose Fluid-Aire Dynamics for Nitrogen Generation Equipment

Nitrogen gas is a critical ingredient in many manufacturing processes around the world. When deciding whether to purchase nitrogen gas through a distributor or purchase an in-house membrane or pressure swing adsorption nitrogen generator, the decision is simple. An in-house nitrogen generator gives you the convenience and flexibility of on-site nitrogen production without having to worry about the logistics, higher cost and environmental impacts of purchasing nitrogen gas from a distributor, not to mention the added safety risks, hazmat requirements and storage space that is required for tank storage.

Fluid-Aire Dynamics offers a selection of membrane and PSA nitrogen generators to fit your particular process needs. To receive a quote for your industrial project, contact us today.

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