How Do Nitrogen Generators Work?
Nitrogen gas is used all over the world for numerous tasks and applications. Some companies and facilities use nitrogen generators to create their own supply of gas, but how do nitrogen generators work?
These generators filter the gas from the air, separate it, filter it, then store pure nitrogen in tanks. Nitrogen generators work by using membranes or pressure swing adsorption (PSA) to filter out impurities, moisture, and other gasses. These nitrogen generators can then go further and create liquid nitrogen.
These nitrogen generators use different methods to separate nitrogen from the air, so let’s see how exactly nitrogen generators work.
What is Nitrogen Used For?
Nitrogen has a variety of uses in the chemical industry, including the production of fertilizer, nylon, pharmaceuticals, and dyes. Nitrogen is also used in food packaging. Nitrogen doesn’t affect fresh food, and it replaces oxygen which will cause food to spoil quickly.
Nitrogen gas can be used in the tire industry. It is used to fill tires which prevents oxidation inside the tire, retains pressure longer, and can offer motorists better gas mileage.
Nitrogen gas is also used in mining industries, electronics, the production of stainless steel, and pollution control. Nitrogen helps to remove VOCs (volatile organic compounds) from liquids before they get discarded.
Liquid nitrogen has many uses as well. The most common use is cryogenic storage of biological samples. (source)
What is a Nitrogen Generator?
Nitrogen generators don’t actually create nitrogen. They only filter the element from the air because our atmosphere contains approximately 78% nitrogen.
Nitrogen is an odorless, tasteless gas present in the air we breathe. In its natural form, nitrogen is considered an inert gas—meaning it does not form bonds with other elements and is mostly non-reactive.
A nitrogen generator is a machine that, much like an air dehumidifier, separates nitrogen gas from the air that passes through it, and stores that gas in another chamber while expelling the unwanted gasses and humidity.
There are two major types of nitrogen generators, membrane nitrogen generators, and pressure swing adsorption generators.
Being able to manufacture one’s own nitrogen gas or liquid is not only economical but is much more efficient. Businesses don’t have to pay to have nitrogen gas transported, which can become expensive. While nitrogen is cheap because it’s found everywhere, there are certain limitations when it comes to transporting the material, especially liquid nitrogen.
Businesses also won’t have to wait for the delivery of nitrogen when they can make their own. As long as the machines are working properly, nitrogen gas is constantly available whenever it’s needed.
How Does a Membrane Nitrogen Generator Work?
A membrane nitrogen generator works by using a series of membranes made up of flexible, semi-permeable cylindrical filaments that trap nitrogen and other particles.
Outside air is compressed and then pushed through these polymer fibers that have holes ranging in size from 0.03 to 10 microns.
These membranes and fibers are stored in cylindrical housings and have such small, microscopic holes that nitrogen molecules are unable to pass.
Oxygen and other smaller molecules are able to pass through the tiny pores and are then exhausted out of the system as waste gas. The nitrogen that is captured is then sent to a holding tank where it can be used.
Moisture and Impurities Have to be Removed
Some membrane nitrogen generators need to use dehumidified air before filtering out the nitrogen. Moisture can settle on these exclusive filters and quickly clog them up rendering them useless until they dry.
But there are some membrane nitrogen generators that already have an air dehumidifier installed. This cuts down on a step and helps to provide cleaner nitrogen gas.
Other filters not only filter out moisture, other gasses, and dust and dirt particles, but a few can actually filter out long-chain hydrocarbons from the air. Long-chain hydrocarbons are VOCs that come from the burning of fossil fuels such as coal, oil, and gasoline.
When attempting to filter nitrogen from the air, the cleaner the gas, the better the end product. With membrane nitrogen generators, you can get 99.95% pure nitrogen gas.
Reducing the impurities such as dirt, moisture, and long-chain hydrocarbons before the air gets to the nitrogen membranes helps to keep the filters working longer.
How Does a PSA Nitrogen Generator Work?
Pressure swing adsorption nitrogen generators work by using materials that nitrogen likes to adhere to under high pressure. Adsorption is where a material clings to the surface of another material instead of going into the material under absorption.
Most PSA generators have two towers. One tower separates the gas by increasing the pressure. The nitrogen will then adhere to a substance such as activated granular carbon, then other gasses, impurities, and moisture pass through.
While nitrogen gas is under pressure and stuck to the adsorbent material, the other contents in the air get sent out as exhaust. Using this technique, nitrogen gas is purified to 99.999%.
How Does a Liquid Nitrogen Generator Work?
A liquid nitrogen generator removes the nitrogen from the air and then it goes one step further to take that gaseous form and either compress or cool it down into a liquid form.
Nitrogen at room temperature and pressure is a gas, but when subjected to immense pressure or extremely cold temperatures it can convert to a liquid form.
Making Liquid Nitrogen Using a Cryocooler
Nitrogen converts into a liquid at -320 °F (-195.8 °C). Once nitrogen gas has been separated from atmospheric air and all the other gasses and impurities have been removed via PSA nitrogen generation, the gas is then channeled into a Dewar flask in the cryocooler where it cools the air to subzero temperatures.
A dewar container is a multi-layer container that has at least one vacuum layer that helps to insulate from the extreme cold and helps to keep more of the liquid inside without building up too much pressure.
Liquid nitrogen boils rapidly at room temperature and can create a lot of pressure which can cause an explosion in a regular container.
Using Air Compression to Create Liquid Nitrogen
Air compression is the other way to create liquid nitrogen. Once the nitrogen has been filtered of all other impurities, moisture, and other gasses it is compressed. When the air is compressed heat is released and the air gets a little cooler.
This process continues to shrink the volume of the air and remove more and more heat until the air is compressed down into a liquid form.
Nitrogen Generator Manufacturers
There are plenty of manufacturers that create, service, and sell nitrogen generators. Whether the generators are needed for pharmaceutical, food and beverage, chemical, analytical, tire filling, or other needs, the following nitrogen generator manufacturers will have whatever is needed.
Compressed Air Systems Inc—Located in Florida, Compressed Air Systems has nitrogen generators for engineering, inspection, and preventative maintenance applications.
Cleatech LLC—This company specializes in membrane nitrogen generators and has several sizes available for small jobs to medium sized applications. They are located in California.
Central Air Compressor Company—Located in Michigan, this company has nitrogen generators for low pressure and high pressure needs in small to medium sizes to larger applications. These nitrogen generators can be used for tire inflating, and many other uses.
Airmatic Compressor Systems Inc—Coming from New Jersey, Airmatic Compressor Systems has both membrane and PSA nitrogen generators. These generators can be used in aerospace, medical, and healthcare applications.
Sutton-Garten Co—This company specializes in nitrogen generation for the beverage industry, tire filling, and industrial applications. They are located in Indiana.
How Much Do Nitrogen Generators Cost?
Nitrogen generators can become quite expensive depending on how big they are, how much nitrogen they created and what options are needed. If nitrogen gas is used all day every day at your facility, then a nitrogen generator could pay for itself in a year.
For the most basic and smallest nitrogen generators, the cost will start around $3,000 to $5,000 and can rise as high as $20,000. Mid-sized generators can start at $20,000 and top out at $100K. Large nitrogen generators which produce enough nitrogen gas for the largest, most demanding jobs start at $100,000.
Customers who need more options such as high-pressure add-ons, skid-mounted packages, air dryers, and more will end up paying much more.
Dry Air is a Necessity
Most nitrogen generators require dry air before working properly, and if the air coming in is not already dehumidified or the generator does not already eliminate the moisture in the air, a compressed air dryer needs to be installed.
In Conclusion
Nitrogen generators are used in so many different aspects of the everyday world. They can use membranes to filter out other gasses, moisture, and impurities until only nitrogen gas remains, or they can use pressure swing adsorption to make nitrogen molecules adhere to a substance while everything else is expelled.
From there, the nitrogen gas can then be compressed or chilled into liquid nitrogen which is often used in storing biological agents for long periods because the liquid is so incredibly cold.
