Activated Alumina for Nitrogen Generation Plants

The atmosphere is filled with abundant nitrogen, around 78%, the remaining 21% consists of oxygen, carbon dioxide, other gases, and argon. There would be surprises in finding out that nitrogen has numerous industrial applications. To utilize the full potential of nitrogen, removing other impurities is necessary. To remove the other impurities, the nitrogen must undergo a PSA (pressure swing adsorption) process. A highly porous desiccant is required to run this process smoothly - Activated Alumina!

In this blog, we will explore the use of activated alumina in nitrogen-generation plants, the purity of nitrogen gas, how it works, and its impact on achieving high-purity nitrogen for industrial use.

What is the Use of Activated Alumina in Nitrogen-Generation Plants?

In PSA nitrogen plants, activated alumina is used in the air pre-treatment stage to remove moisture from the compressed air before it reaches the system's nitrogen-separating parts. Let's break down the role of activated alumina in detail.

• Drying the Air

Compressed air naturally contains other compounds and water vapor, which is why it's necessary to eliminate them; otherwise, they would cause a great deal of harm to the pieces of equipment as well as the gases. Activated alumina is widely used for drying air due to its high porosity, which helps in holding and trapping the water particles from the air. The ultimate goal is to obtain a purer form of nitrogen, and activated alumina makes it achievable; no water reaches the adsorption towers.

• Protecting the CMS

Carbon molecular sieves (CMS) are used to separate other impurities, such as oxygen and carbon dioxide, from nitrogen. The CMS must be protected to keep it effective, as they are sensitive to moisture. Activated alumina protects the CMS by removing water first and helping it work better and longer.

• Pre-Filtration Role

Activated alumina doesn't work alone; it is also a part of the pre-treatment system with activated carbon that removes oil and other volatile organic compounds. Secondly, other particulate filters that trap dust and other solid particles.

What is the Purity of Nitrogen Gas?

The availability of nitrogen on planet Earth is abundant, plus it is an inert gas, which means that it does not readily react with other substances. Before discussing more of its properties, we want to tell you that these two properties make it perfect for many industrial applications.

However, we can't use them directly; they must be purified. Nitrogen generation plants, or PSA nitrogen gas plants, create nitrogen gas on-site for various industrial applications. They separate nitrogen from the air and other impurities, such as water and carbon dioxide, producing purified nitrogen; the separation process is known as Pressure swing adsorption.

The purity of nitrogen gas indicates how clean it is, how free it is from other substances, and how much of the gas is nitrogen. As discussed earlier, nitrogen, when in its impure form, contains other substances (impurities) such as water vapor, carbon dioxide, carbon monoxide, and water vapor.

Certain industries can use nitrogen even if it contains impurities, while others require a pure form. Here is detailed information on the contents of low—and high-purity nitrogen.

• Low-Purity Nitrogen

It's not always necessary for low-purity nitrogen to be inadequate or useless if it contains other substances and the nitrogen content is between 90% and just under 98%. It can be called low-purity nitrogen.

However, it works well in food packaging and general manufacturing areas. Low-purity nitrogen is sold under other names such as pre-purified, extra dry, industrial grade, and oxygen-free.

• High-Purity Nitrogen

Most nitrogen must undergo a process to obtain this purity level, at least 99.998% pure nitrogen. That means only a tiny amount, less than 0.002%, can be other gases.

The sum of oxygen ought to be less than 0.5 ppm, water vapor ought to be less than three ppm, hydrocarbons ought to be less than 0.5 ppm, and carbon monoxide ought to be less than one ppm.

High-purity nitrogen, also known as zero-grade nitrogen, is very useful in industries such as laboratories, pharmaceuticals, and electronics.

How do PSA Nitrogen Generators Work?

The PSA nitrogen generators are used to make pure nitrogen gas from the surrounding air. The process by which the pure form of nitrogen is obtained is known as pressure swing adsorption (PSA).

Nitrogen is not pure; it combines with other gases in the air, such as oxygen. Pressure swing adsorption is a method that is used to make pure nitrogen gas from the surrounding air through PSA nitrogen generator machines. Here, we will introduce you to adsorbent, but first, let's understand how the PSA works. Regular air is taken—regular generator.

Then nitrogen is separated from it, using adsorbents - it traps the oxygen and lets nitrogen pass through. Adsorption and desorption are the two essential steps that take place within the nitrogen generator -

Adsorption-

First, clean compressed air is sent into a vessel (a large container) filled with Carbon Molecular Sieves (CMS) and Activated Alumina. The activated alumina and carbon molecular sieves act as a trap, holding other gases and oxygen and letting the nitrogen pass through. The nitrogen that comes out is much cleaner and ready to use.

Desorption -

When the adsorbents become full and lose the capacity to hold on to any more oxygen, the system releases the pressure, and the released oxygen is known as desorbed. Next, the desorbed oxygen is vented out into the atmosphere. To keep the nitrogen flowing continuously, the PSA system uses two vessels that work in turn. One vessel generates nitrogen, and the other cleans itself by releasing the trapped gases.

What are the Main Materials Used in the PSA Nitrogen Generators?

While there are different types of adsorption media used in the PSA nitrogen generators, activated alumina balls are the most common and widely used due to -

• High porosity - The activated carbon has a highly porous structure with a wide surface area (500-1500 m²/g), which can adsorb organic compounds efficiently, such as vapor odors from the compressed air feed.
• Selective removal of impurities—The commonly found impurities are easily removed from compressed air, ensuring that only clean air enters the PSA towers, which helps improve the purity of nitrogen.
• Chemical stability - It is chemically inert and stable under the operating conditions of PSA systems, resisting degradation from moisture.
• Regenerable and reusable—Activated carbon can be cleaned and reused during the low-pressure part of the cycle in PSA (Pressure Swing Adsorption) systems.

Applications of Nitrogen Gas -

• Food Industry
• Fire Suppression System
• Tire Filling System
• Aircraft fuel system, Chemical Analysis, and Chemical Industry
• Pressurized Beer Kegs
• Aircraft Fuel System
• Light Bulbs Industry
• Electronics Manufacturing
• Oil and Gas