Many of today’s manufacturing processes require large amounts of oxygen, nitrogen, and other pure gases in a continuous stream. The atmosphere can be a ready source of many of these gases, containing nominally 78% nitrogen, 21% oxygen, .9% argon, and traces of other gases. Large amounts of these gases may be required for large scale commercial applications such as food packaging, cutting/brazing/soldering, enhanced oil recovery, and other industries, including chemicals and oil and gas/power generation.
Historically, gases such as oxygen and nitrogen have been “distilled” from the atmosphere by various cryogenic processes. The history of the cryogenic separation is quite extensive with several global companies providing product. The main advantage of cryogenic separation is the ability to produce and supply large quantities of highly concentrated purified gas/liquid used for larger volume requirements. A significant disadvantage is that cryogenic separation is very energy intensive, consuming electricity to achieve and maintain temperatures required for the gas separation process and the long-term storage of liquefied gases in cryogenic liquid supply cylinders.
In the past few decades, some alternatives to the cryogenic gas separation process have evolved. In particular, Membrane and PSA (Pressure Swing Adsorption):
Membrane technology uses hollow fiber membranes (made of man-made polymers) to separate nitrogen and oxygen by molecular size from clean/dry compressed air stream “non-cryogenically” or “gas phase-to-gas phase” separation and the purified nitrogen is directed to the process and enriched oxygen is vented back to the atmosphere from which it came.
PSA technology for nitrogen utilizes a carbon molecular sieve that “non-cryogenically” adsorbs the smaller oxygen molecules and any remaining water/vapor that allows the highly-enriched nitrogen molecules to pass through the bed to become high purity process gas while the enriched oxygen desorbs.
While each of these technologies have their own particular strengths and weaknesses depending on their application, they share the same benefits as summarized below:
- Highly cost-effective
- Produces nitrogen from an independent compressed air source
- Rapid startup and easy installation
- On-demand production (no vaporization loss)
- Low cost maintenance and repair (consumable parts such as filter, oil changes, etc.)
- Customization options available upon request
- Automated systems capable of long term unattended operation, collecting and transmitting operational parameters to remote locations for process management, and diagnostics and prognostics for condition-based maintenance
- PLC process control (standard color HMI screen and oxygen analyzer are standard on PSA units, however, a flowmeter is optional)
AirSep Membrane Nitrogen Systems
Unlike cryogenic systems, AirSep will have Membrane-based nitrogen products available that are compact, easily transportable, and compatible with a myriad of oil and gas onshore and offshore applications (especially in the hydrocarbon processing industry).
Clean, dry compressed air enters one end of a permeable membrane. The smaller oxygen molecule and other “fast” gases (such as carbon dioxide), including any remaining water vapor (H2O) passes through the fiber outside wall first and is then released as a permeate stream back again to the atmosphere. The larger molecules or “slower” gases (nitrogen) pass through the opposite end of the module as the desired product gas to the actual intended process.
A few distinct advantages of membrane nitrogen technology are the simplified packaging, requiring significantly fewer moving parts, both horizontal and vertical design packaging and the ability to be containerized for easy transport by truck or ship, globally. AirSep can build complete turn-key packages with compressors, dryer’s and gas boosters, that can increase
nitrogen gas pressure ranging from 250 – 3000 psig (or higher) for re-filling high pressure cylinder’s. Systems are also packaged with pre-filters, a carbon filter, and a membrane filter.
AirSep membrane systems produce less noise and take up only a small footprint.
The need for high purity nitrogen is not as critical since the Lower Explosive Limits (LEL) or remaining tolerable oxygen level determines the minimum level of nitrogen purity that needs to be present while sharing the same contained space with hydrocarbons or other combustible gases, yet still remain stable or (non-explosive). For an example, Methane-CH4 has an LEL of 8 – 10% oxygen. If the level of oxygen is held at 5%, it is considered to be stable, however, if the percentage reaches 8% oxygen, it would be considered unstable and could possibly explode in the case of a spark or some other source of ignition. Membrane technology is the most efficient by having the highest percentage of nitrogen recovery from compressed air feed, especially when considering 95 – 97% nitrogen concentration.
- Capable of high volumetric nitrogen flowrates at 98% and higher, economically
- Available with capacities up to 78,000 SCFH (2,050 Nm3/hr)
- Product dew point at -65ºF (-54ºC)
- Can be fabricated in accordance with all relevant local codes
AirSep PSA Nitrogen Systems
AirSep PSA Nitrogen Systems use at least two vessels filled with carbon molecular sieve as adsorbers. As compressed air passes through one of the adsorbers, the carbon molecular sieve adsorbs the oxygen and remaining water vapor first. This allows the separated nitrogen to pass through the upper nozzle outlet connection of the adsorber vessel, and then is stored in the nitrogen buffer tank. Before the adsorber becomes saturated with oxygen and breakthrough occurs, both the inlet air and the nitrogen outlet valve close and the partially pressurized vessel equalizes with the second adsorber that is waiting to come online. This allows for a pre-charging of the second adsorber before the first adsorber is then regenerated by desorbing the remaining adsorbed enriched oxygen gas through a depressurization cycle step. The complete cycle is then repeated. Under normal operating conditions, the carbon molecular sieve is completely regenerated and will last indefinitely.
Stationary two-bed Standard PSA Nitrogen Generators, Containerized Shipboard Systems, as well as expandable, cabinet-mounted Modular PSA Series gas generators, are now offered by AirSep. AirSep standard PSA Generators are available with capacities up to 45,000 SCFH or (1,275 Nm3/hr) and may be placed on an existing foundation, or skid-mounted as a turnkey system with compressors, dryers and pre-filtration. PSA technology is ideal for higher purity applications at or above 99.5 – 99.995%. Cylinder-fill options are available upon customer request. For special applications, an optional high purity catalytic module can be added to the cylinder refilling plant to increase nitrogen concentration to 99.999% ±0.5%.
Each AirSep PSA Nitrogen System is equipped with a NEMA 4 HMI multi-color touchscreen control panel with an integrated nitrogen monitor that supports several different languages, remote monitoring, email notifications, maintenance alarms, data logging, and much more.
- Available with capacities up to 45,000 SCFH (1,182 Nm3/hr)
- Product pressure at 85-90 psig
- Product concentration at 99.5% and higher
- Product dew point at -100ºF (-73ºC)
- Expected power consumption of 3.2 kWh ±10% SCFH of total flow, nominal 99.5% nitrogen at up to maximum 85 psig product pressure at maximum plant capacity
- Can be fabricated in accordance with all relevant local codes and standards
Generate a Significant Return on Investment (ROI) with an AirSep Nitrogen Generator
Purchasing and operating an AirSep nitrogen generator vs. delivered liquid nitrogen results in cost savings up to 50% or higher. In most cases, a customer would achieve return on investment in less than two years (depending upon a two-shift usage cycle). The greater the number of operating hours that the gas generator is used, the faster the capital return on investment.
Delivered liquid nitrogen under contract is subject to cost increases due to delivery surcharges, electrical Kwh/hr costs and other expenses. The safer and more reliable option is to make your own gaseous nitrogen on-site and on-demand. A non-cryogenic nitrogen generator offers price stability in the long-run.
After receiving a “payback” on investment, the savings continue to grow, especially in areas such as delivery, operation, and even safety costs. The generator will pay for itself and improve efficiency. These low-maintenance generators offer a continuous, uninterrupted supply for nitrogen.
AirSep Corporation is located in Buffalo, NY and has been an experienced and professional player in PSA and VPSA Oxygen Systems since the 1980’s. AirSep is proud of its non-cryogenic air separation facilities, which fill an important niche in the rapidly evolving manufacturing landscape. AirSep now offers Membrane and PSA non-cryogenic air separation technologies for nitrogen generation. AirSep nitrogen generators run efficiently producing nitrogen gas on their own, as needed. They eliminate bulk deliveries and are fully automated and easy to maintain.
AirSep Membrane and PSA nitrogen systems are available in several different sizes and concentration levels. Visit AirSep’s website for more information on gas generation products and learn how they can fulfill the requirements of many various commercial applications; www.airsepcpd.com.