Multiple industries use nitrogen to perform core business operations. Business owners may rent liquid nitrogen tanks or high-pressure cylinders on an as-needed basis. However, there is a more cost-effective option.
The atmosphere is 78% nitrogen. You can harness this abundant resource with a nitrogen generator. These machines separate nitrogen from the air to provide nitrogen on demand.
The two types of nitrogen generators are pressure swing adsorption (PSA) and membrane generators. Choosing between the two depends on your nitrogen purity, pressure, and flow requirements. In this guide, you will learn more about the distinct types of nitrogen generation and how to find the right one for your application. It is best to collaborate with experts — like Liberty System Sales Engineers — to size it properly.
How Does a Nitrogen PSA Generator Work?
PSA generators separate nitrogen gas from compressed air by passing it through a carbon molecular sieve (CMS). These sieves have precise and uniform pores that absorb oxygen, carbon dioxide, water vapor, and other impurities. The nitrogen molecules bypass the CMS rather than being caught by it, at which point you can either collect and store or use the nitrogen immediately.
The CMS will eventually become saturated with oxygen molecules, which will prevent further gas separation. To ensure continual operation, PSA generators contain two CMS absorption beds. When one sieve bed becomes full, the generator switches to the other sieve bed. It then depressurizes and flushes the saturated CMS with nitrogen gas. This process removes the oxygen molecules from the sieve, which the generator releases as waste gas.
How Does a Membrane Nitrogen Generator Work?
Membrane nitrogen generators function by using a membrane separation technique. They contain semipermeable membranes made of hollow polymer fibers. While the PSA’s CMS absorbs oxygen, these membranes have a unique structure that allows select molecules to pass through. The air compressor pushes compressed air through the membrane and relies on the different gas permeability rates to separate the nitrogen from the other gases.
Once the nitrogen is separated from the oxygen and other gases, it is ready to use and apply to your process. The generator controls the pressure, purity, and gas flow through the system to ensure effective gas separation.
Key Differences Between PSA and Membrane Nitrogen Generators
PSA and membrane nitrogen generators each have their advantages and disadvantages. Understanding these and how the machines differ will help you choose one for your application. Below are the main differences and advice for choosing between the two types.
1. Purity Levels
The most essential factor to consider when choosing between PSA and membrane generators is the nitrogen purity levels. Nitrogen gas is considered either low or high purity depending on the ratio of nitrogen to oxygen. High-purity nitrogen has a 99.95% or greater nitrogen purity, while low-purity has a range of 90% to 99.9%. Ultra-high-purity nitrogen has a purity level of 99.999%.
Nitrogen generators offer varying nitrogen purity levels:
- PSA generators:
Thanks to the effective CMS, PSA generators can produce high- and ultra-high-purity nitrogen. This resource is essential for industries and processes that are sensitive to oxygen and other contaminants. Examples include drug manufacturing, metal heat treatment and electronic circuit production. - Membrane generators:
Membrane generators produce nitrogen at a lower purity level — between 95% and 99.9% — making them suitable for low-purity nitrogen applications. These use cases include blanketing adhesives, food packaging, purging pipelines, and filling the ullage or vapor space above the fuel in a commercial jet.
