The gas separation process in PSA N2 generators is based on the ability to fix various gas mixture components and particles by a physical solid substance. These are called adsorbents.
PSA process illustration
The technology of air-to-nitrogen generation with the use of adsorption processes in PSA nitrogen generators is well studied and widely applied at industrial facilities for the recovery of high-purity nitrogen. This is then used in many industries from food packaging to supporting laboratory instrumentation such as Liquid Chromatography Mass Spectrometry (LC-MS) and Gas Chromatography (GC).
PSA nitrogen generators for these scientific applications are designed to produce high purity nitrogen by regulating gas adsorption and adsorbent regeneration by changing pressures in two adsorber-adsorbent containing vessels. This process requires a constant temperature, close to ambient.
The swing adsorption process in each of the two adsorbers consists of two stages running at intervals of a few minutes. At the adsorption stage oxygen, moisture and carbon dioxide molecules diffuse into the pore structure of the adsorbent whilst the nitrogen molecules are allowed to travel through the adsorber–adsorbent-containing vessel to be delivered as high purity nitrogen to the application.
Nitrogen generators allow for the production of high purity nitrogen from the surrounding atmosphere, which can provide – up to 99.% nitrogen depending on the nitrogen generator system.
Nitrogen generators allow for continuous operation 24/7, giving you an uninterrupted flow of gas when it's needed.
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The application of the nitrogen gas can be diverse and altered at short notice. So long as the nitrogen generator can meet the flow and purity requirements of the application it can be changed from one day to the next with minimal hassle.
By substituting out-of-date cylinder technology, on-site nitrogen production savings largely exceed 50% for a typical LC-MS application. The net cost of nitrogen produced by nitrogen generators is significantly less than the cost of bottled or liquefied nitrogen.
On-site generators are highly resistant to vibration and shocks, chemically inert to greases and moisture insensitive. With proper, planned, in most cases annual, maintenance a generator can easily last a decade or more.
A gas generator purchase can be a significant initial purchase. However, labs can quickly recoup the initial cost through savings of alternative supplies of gas (such as nitrogen cylinders) in less than 12 months.
Purity is directly related to flow rate. High purity-high flow rate nitrogen generators are more expensive, nevertheless the solution will still be cheaper in the long run when compared with bulk gas supply.
For a free no obligation quotationWhen producing your own nitrogen, it is important to know and understand the purity level you want to achieve. Some applications require low purity levels (between 90 and 99%), such as tire inflation and fire prevention, while others, such as applications in the food and beverage industry or plastic molding, require high levels (from 97 to 99.999%). In these cases PSA technology is the ideal and easiest way to go. In essence a nitrogen generator works by separating nitrogen molecules from the oxygen molecules within the compressed air. Pressure Swing Adsorption does this by trapping oxygen from the compressed air stream using adsorption. Adsorption takes place when molecules bind themselves to an adsorbent, in this case the oxygen molecules attach to a carbon molecular sieve (CMS). This happens in two separate pressure vessels, each filled with a CMS, that switch between the separation process and the regeneration process. For the time being, let us call them tower A and tower B. For starters, clean and dry compressed air enters tower A and since oxygen molecules are smaller than nitrogen molecules, they will enter the pores of the carbon sieve. Nitrogen molecules on the other hand cannot fit into the pores so they will bypass the carbon molecular sieve. As a result, you end up with nitrogen of desired purity. This phase is called the adsorption or separation phase. It does not stop there however. Most of the nitrogen produced in tower A exits the system (ready for direct use or storage), while a small portion of the generated nitrogen is flown into tower B in the opposite direction (from top to bottom).
This flow is required to push out the oxygen that was captured in the previous adsorption phase of tower B. By releasing the pressure in tower B, the carbon molecular sieves lose their ability to hold the oxygen molecules. They will detach from the sieves and get carried away through the exhaust by the small nitrogen flow coming from tower A. By doing that the system makes room for new oxygen molecules to attach to the sieves in a next adsorption phase. We call this process of ‘cleaning’ an oxygen saturated tower regeneration.
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