Nitrogen generators generate pure nitrogen gas on site by separating it from natural air. We all know, air is about 78% nitrogen by volume. So, the nitrogen unit compresses this air and then uses special materials to remove oxygen and other impurities. The result is a continuous flow of high purity nitrogen for industrial use.
Read on to learn the main principles, components and simple setup tips for on site nitrogen generation units.
Nitrogen Production Principles
Air Separation:
One of the methods for nitrogen production is cryogenic air separation. In this process, air is cooled till it becomes liquid. Then distilled to separate nitrogen and oxygen. This method reaches to very high purity but needs large and complex equipment. Cryogenic plants are basically used for very high volume production because they are costly and energy intensive.
Pressure Swing Adsorption (PSA):
On-site nitrogen generators mostly use PSA technology. This technology works by trapping oxygen and other gases on an adsorbent under pressure but leaving nitrogen as the output. Compressed air is sent into a vessel filled with carbon molecular sieve (CMS). Oxygen molecules stick to the CMS. But the large nitrogen molecules flow through as purified nitrogen. Basically, there are two towers that work in parallel: one tower adsorbs oxygen and the other one regenerates (releases the adsorbed gases). The both towers switch roles from time to time. This alternating process actually makes sure a continuous supply of nitrogen gas.
Nitrogen Purity Levels
Industrial Grade Nitrogen: Industrial applications most commonly use almost 95% to 99.9% pure nitrogen. This “industrial grade” nitrogen may contain higher levels of residual oxygen or argon. But this is acceptable for many processes. It is used for purposes like blanketing, purging, food packaging and metal processing where extreme purity is not pivotal. Thus, “industrial grade nitrogen generators” are simpler and have lower operating costs.
Ultra High Purity Nitrogen: Some applications need extremely pure nitrogen, usually 99.999% purity or higher. This “ultra-high purity” nitrogen has the only ppm (parts-per-million) levels of impurities. And this purity is much needed in semiconductor manufacturing, pharmaceuticals, aerospace and other precision industries. For achieving this ultra high purity, you basically need more stringent separation plus extra purification stages.
System Components
- Air Compressor:First, you need to have a dedicated air compressor that provides the high pressure compressed air needed for nitrogen generation. So, air compressors that are used for this purpose are mostly oil free compressors or have filters. Moreover, your compressor must supply sufficient flow at the needed pressure (commonly around 4-13 bar) to meet the generator’s needs.
- Air Dryer:The second thing is air dryers. Before air enters the PSA towers, it passes through an air dryer. This dryer removes moisture from the compressed air. Basically, a desiccant or refrigeration dryer is installed after the compressor and before the generator to achieve a low dew point.
- Molecular Sieve Beds:The core of the unit is Molecular sieve bed. That consists of two or more adsorber vessels filled with carbon molecular sieve (CMS). These beds do the actual separation. Each vessel is packed with a CMS that specifically adsorbs oxygen (also sometimes carbon dioxide).
When compressed air enters a bed, oxygen molecules are trapped by the CMS and nitrogen passes through. This leaves the output gas that is highly pure nitrogen. After some time, this saturated bed is gone offline and depressurized but the other bed takes over. This twin bed principle allows one bed to adsorb and the other regenerates for continuous operation.
- Control Valves and Piping:A network of valves and piping directs airflow through the system. These valves switch the feed air between the two adsorber towers. Plus they control the timing of pressurization and venting.
Moreover, piping connects the compressor, air dryer, vessels and nitrogen outlet. So, proper piping design makes sure the intake air is clean and a stable nitrogen output.
Exhaust lines are also piped to safely vent the expelled oxygen and other impurities into the atmosphere.
Working Principles
Pressurization and Depressurization:
The system operates by cycling each adsorber through high pressure and low pressure phases. In the adsorption phase, one vessel is pressurized with dry air. In the regeneration phase, the other vessel is depressurized to purge the adsorbed gases.
While one tower is capturing oxygen under high pressure, the other one is depressurized to release its collected oxygen. Then they switch roles. This pressure “swing” allows continuous nitrogen production.
Adsorption and Desorption Cycles:
During the adsorption stage, compressed air enters an adsorber vessel. Then, oxygen molecules bind (adsorb) to the carbon sieve and nitrogen passes through as product. This adsorption phase continues till the CMS in that vessel becomes saturated with oxygen.
Now, the system isolates that vessel and opens its exhaust to lower pressure. The drop in pressure causes desorption: the oxygen (and moisture) detach from the sieve and are expelled. This restores the capacity of adsorbent. By changing these adsorption/desorption cycles between the two vessels, the generator maintains a steady nitrogen output.
Oxygen Removal Procedure:
The carbon molecular sieve is key to oxygen removal. CMS has tiny pores that selectively adsorb smaller molecules like oxygen and water vapor, while larger nitrogen molecules pass by. In practice, when air enters the vessel, oxygen “sticks” to the sieve surface. During regeneration, released oxygen is pushed out by a small stream of nitrogen or simply by venting. The expelled oxygen is sent out of the system as waste gas. Over many cycles, this selective adsorption removes the majority of oxygen from the air, so the remaining gas is mostly nitrogen.
Installation and Setup
Site Preparation:
The first thing is preparation of the site. As proper installation starts with this. Also, make sure the foundation is stable and leveled to support the equipment and reduce vibration. Plus, the selected site must be well ventilated to dispel heat and any purged gases.
Electrical and Utility Connections:
The generator must be tied into the facility’s systems. This includes wiring it to the electrical panel with proper grounding and circuit protection. If the unit has a built-in compressor, it will have its own power requirements; if not, connect the outlet of the shop air compressor to the generator inlet.
Also, install piping for the nitrogen output to the point of use and for the exhaust line. According to installation guides, all air intake, nitrogen output and vent lines should be correctly sized and securely fitted.
Safety Considerations:
Safety is very important with gas generators. The room must be ventilated so that any leaked nitrogen (an inert gas) does not accumulate and displace oxygen.
Install the unit such that exhaust and vent lines discharge outdoors or into a safe area.
Also, pressure relief valves must be fitted on vessels to prevent overpressure and these along with other safety devices, must be tested regularly.
Operators should be trained on safe handling. For example: as pure nitrogen is odorless. So, installations mostly include oxygen monitoring alarms in closed spaces.
By following best practices, the nitrogen generator can be used without risk to personnel or equipment.
FAQs
What is the lifespan of a nitrogen generator?
Mostly well maintained nitrogen generator units have a lifespan of 15-30 years. Core parts like compressors or molecular sieve beds need periodic service or replacement. With proper service and maintenance, some systems can run 30+ years.
Are nitrogen generators expensive?
Their prices vary a lot by their type and size. Small membrane units can start around $1,000; lab or high-purity PSA systems mostly start several thousand.
What are the common problems with nitrogen generators?
Nitrogen generators can face problems such as low purity, pressure drops, air leaks, clogged pre filters or valve failures.
How efficient are nitrogen generators?
Efficiency depends on tech, design, duty cycle and purity needs. PSA gives better air to nitrogen ratios for high purity. Membrane systems use less energy for lower purities.
Want to read more:
Is Nitrogen Better Than Compressed Air for Laser Cutting?
How to Choose the Best Nitrogen Generator for Your Laser Cutting Machine
What pressure is needed for nitrogen laser cutting?
How to Choose Air Compressor Distributor?
