What is membrane nitrogen generation?

Nitrogen plays a pivotal role in various industrial sectors, thanks to its inert properties. 

In food and beverage packaging, it extends shelf life by displacing oxygen, preventing spoilage, and preserving freshness. Pharmaceutical manufacturers use nitrogen to ensure the stability and purity of their products by creating an inert atmosphere that prevents oxidation and contamination. In chemical processing, nitrogen is used for blanketing and purging, safeguarding sensitive reactions and maintaining the integrity of the process.

These industries need a 95% mix (or better) of pure nitrogen for commercial purposes.

Traditionally, industries relied on deliveries of nitrogen gas in cylinders or bulk tanks, which can be cumbersome, expensive, and prone to supply disruptions. However, a paradigm shift is occurring with the emergence of on-site nitrogen generation using membrane separation technology. 

This innovative approach allows businesses to produce their own source of nitrogen supply directly at their facility. It eliminates the need for external deliveries, offering greater control over production and ensuring a continuous supply of nitrogen.

Membrane Nitrogen Generation

Membrane nitrogen generation produces nitrogen gas on site from compressed air. These systems work through thousands of hollow fibres that let oxygen pass through while keeping nitrogen in the main flow.

Membrane nitrogen generators need dry, clean air to function properly. Wet air clogs the membranes, which means more maintenance and shorter membrane life. Most setups include coalescing filters that need to be changed every 6,000 hours to remove particulate and oil.

Unlike PSA nitrogen generators, membrane generators do not cycle between adsorption vessels. They are quieter but use more power for high-purity output. A 50 Nm³/hr system typically draws about 22 kW when producing 99% pure nitrogen.

The membranes themselves last about 5 years with proper filtration. Replacement costs roughly £3,000 for a mid-sized unit. The control panel is straightforward, just pressure gauges, a purity monitor, and power indicators.

Most users report that the technology is quite reliable. Breakdowns are rare, though cold winter mornings sometimes cause condensation issues if the intake air is not properly heated.

How Does Membrane Technology Work?

To understand how nitrogen generators work, we must look at the internal components. With a nitrogen membrane generator, small membrane modules store polymer fibres inside. These consist of thousands of hollow fibres which allow both air flow and the separation process to occur.

Permeation: What is it?

Permeation is a process whereby compressed air enters, first inside the membrane modules, and later the polymer fibres themselves. As previously cleaned, high-pressure compressed air moves through the fibres, it helps to separate distinct elements.

During gas separation, molecules such as oxygen, H2O, carbon dioxide, and air impurities permeate the membrane fibres. This permeation process occurs at a different rate depending on the element.

Fast-permeating gases like H₂O, CO₂, and oxygen are quickly removed, while larger nitrogen molecules, which act as a ‘slow’ gas, are retained at desired purity levels​.

H2O is removed very quickly, whereas oxygen lags a little. Argon, which is present at a roughly 1% rate in Earth’s atmosphere, will partially permeate when given time to do so. However, some Argon will still be present with the remaining nitrogen.

It’s All About the Membranes

The membranes have a concentration gradient surface on either side. This allows for distinct elements to permeate the sides while nitrogen flows through the hollow fibres unimpeded.

Atlas Copco’s NGM membranes are tailored to specific industrial requirements, with pore sizes engineered to achieve precise purity levels needed for industries like food, beverage, and pharmaceuticals​​.

When it comes to N2 purity, the size of the individual pores within the membranes is a significant factor. Therefore, the membranes are specific to the purpose and the purity levels required.

The Need for Venting

No waste gas is expelled during the N2 membrane-based production process. Venting so-called “fast exhaust gasses” is necessary, though, including Argon, H2O, and oxygen. Without doing so, the polymer fibres eventually become clogged, and permeation efficiency suffers. Then purity levels decline sharply too.

Membrane nitrogen generators from Atlas Copco include advanced venting mechanisms to sustain long-term operational efficiency without compromising purity​.

Membrane-based generators include a permeate vent to address this issue.

Technical Capabilities and Standards

Modern generators are designed to meet strict industry standards. For example, the Atlas Copco NGM and NGM+ series provide a flexible solution for varying needs:

• Purity and flow rate: These systems can achieve nitrogen purity up to 99.5% with flow capacities reaching up to 800 Nm³/h for the NGM+ series.
• Operating Conditions: They function effectively within a pressure range of 4 to 13 bar and temperatures from 5°C to 50°C.
• Air Quality: To protect the membrane nitrogen technology, the intake air is typically treated to ISO 8573-1 standards (Class 1 for oil and particles is recommended) to prevent fouling.

This combination of pressure and flow rate control allows the generator to be tuned exactly to your production requirements.

Benefits of Using a Membrane Nitrogen Generator

Membrane nitrogen generation is a superior solution for many industries. By producing nitrogen on-site, businesses gain control, cut costs, and reduce their environmental impact. Let’s explore why you should learn how membrane systems can transform your operations.

Cost Efficiency

Membrane nitrogen generation offers a compelling advantage in terms of cost efficiency. Unlike traditional methods like cryogenic distillation, which require significant energy input to separate nitrogen from the air, membrane technology operates at lower pressures and temperatures. This translates to a substantial reduction in energy consumption and, consequently, lower operational costs.

Membrane nitrogen generators eliminating the need for frequent deliveries of nitrogen cylinders or bulk tanks further contributes to cost savings. Even storing nitrogen cylinders costs real estate and space.

For businesses that rely on a consistent and reliable supply of nitrogen, the cost-effectiveness of membrane generators can lead to a rapid return on investment. By reducing energy bills and eliminating delivery charges, membrane nitrogen generation becomes an attractive option for long-term cost optimization.

Purity and Control

One of the most significant advantages of membrane nitrogen generation is the ability to tailor nitrogen purity to specific industrial requirements. Membrane systems can produce nitrogen with purities ranging from 95% to 99.5%. This flexibility allows businesses to fine-tune their nitrogen output to match the exact purity needed for their processes, avoiding unnecessary overproduction of high purity nitrogen gas, which is wasteful and costly.

This flexibility aligns with the demands of pharmaceuticals and food packaging industries, avoiding unnecessary costs associated with over-specification​​.

This precise control over nitrogen purity not only ensures optimal performance in various applications but also contributes to cost efficiency. By generating nitrogen at the required purity level, businesses can avoid paying for higher-purity nitrogen than they need, further maximising the economic benefits of membrane technology.

Simplicity and Reliability

Membrane nitrogen generators are renowned for their simplicity and reliability. Unlike complex cryogenic distillation systems, membrane generators have a straightforward design with fewer moving parts, making them less prone to breakdowns and requiring minimal maintenance. This translates to greater uptime and reduced maintenance costs.

Atlas Copco designs its generators with plug-and-play functionality, ensuring quick installation and minimal personnel training​.

The ease of installation is another advantage of membrane technology. These systems are compact and modular, requiring minimal floor space and infrastructure. Their straightforward operation means that personnel with minimal training can effectively manage the nitrogen generation process. This combination of simplicity and reliability makes membrane nitrogen generation a dependable choice for businesses seeking a continuous and hassle-free nitrogen supply.

Environmental Advantages

Membrane nitrogen generation is not only economically sound but also environmentally friendly. Unlike traditional methods, which often involve energy-intensive processes and transportation of nitrogen in heavy cylinders or tanks, membrane technology has a smaller carbon footprint. By generating nitrogen on-site, businesses can reduce their reliance on transportation, minimising emissions associated with deliveries.

On-site generation eliminates transportation-related emissions and ensures compliance with sustainability goals​​.

Furthermore, the lower energy requirements of membrane generators contribute to a more sustainable approach to nitrogen production. By choosing membrane technology, businesses can be environmentally responsible and friendly all at a cheaper operational cost.

How Membrane Technologies Compare to Pressure Swing Adsorption (PSA)

Nitrogen can be generated on-site using either nitrogen separation membrane techniques or pressure swing adsorption (PSA). Both methods use compressed air as the source material.

Membrane systems push air through hollow fibres that let oxygen escape through their walls.

PSA nitrogen generation technology works differently. It uses carbon molecular sieves that trap oxygen while letting nitrogen pass through. The beds switch back and forth, one adsorbing while the other regenerates. A medium-sized PSA unit from a UK manufacturer contains roughly 200 kg of carbon sieve material.

The differences matter for practical reasons. PSA systems achieve higher purities, up to 99.999%, but consume more power.

Maintenance requirements differ, too. Membrane filters need changing every 6 months, while PSA systems require valve servicing roughly every 8,000 operating hours.

PSA generators make some noise during the switching cycle, about 75 dB at one metre. Membrane units run more quietly at around 65 dB. This matters in confined spaces or when installed near office areas.

Membrane systems take up less room, about half the footprint of equivalent PSA units. A standard 100 Nm³/hr membrane generator measures roughly 1.2 × 0.8 metres, while the PSA alternative needs 2.3 × 1.1 metres of floor space.

Applications of Membrane Nitrogen Generators

Membrane nitrogen generators find use in a wide array of industries due to their reliability, cost-effectiveness, and ability to deliver nitrogen at the required purity. Here are some key applications:

• Food and Beverage: Modified atmosphere packaging (MAP) uses nitrogen to extend the shelf life of perishable goods by displacing oxygen and preventing spoilage. This is crucial for maintaining freshness and quality in packaged foods.
• Pharmaceuticals: Nitrogen blanketing protects sensitive pharmaceutical products from oxidation and contamination during manufacturing and storage, ensuring product integrity and efficacy.
• Chemical Processing: Nitrogen is used for purging and blanketing in chemical reactors and storage tanks to prevent unwanted reactions and maintain a safe environment.
• Electronics: In electronics manufacturing, nitrogen provides a dry, inert atmosphere for soldering and component assembly, preventing oxidation and ensuring high-quality connections.
• Laser Cutting: Nitrogen is used as an assist gas in laser cutting to remove molten material and protect the laser optics, resulting in clean and precise cuts.
• Oil and Gas: Nitrogen is used for pipeline purging, pressure testing, and enhanced oil recovery (EOR) to improve efficiency and safety in oil and gas operations.
• Aerospace: Nitrogen is used in aircraft fuel tank inerting systems to prevent explosions and enhance safety during flight.

Troubleshooting Common Membrane Nitrogen Generator Problems

While membrane nitrogen generators are generally reliable, some common issues can arise. Here’s a troubleshooting guide:

• Low Nitrogen Purity:
  • Possible Cause: Membrane damage, insufficient pre-filtration, leaks in the system.
  • Solution: Inspect membranes for damage and replace if necessary. Check and replace pre-filters regularly. Inspect all connections for leaks and repair as needed.
• Reduced Nitrogen Flow Rate:
  • Possible Cause: Clogged membranes, insufficient compressed air supply, pressure drops in the system.
  • Solution: Clean or replace membranes. Ensure the compressed air supply meets the generator’s requirements. Check for pressure drops and address any restrictions in the piping.
• High Pressure Drop:
  • Possible Cause: Clogged filters, restricted airflow, membrane fouling.
  • Solution: Replace filters regularly. Ensure adequate airflow to the generator. Clean or replace membranes if fouled.
• Excessive Noise:
  • Possible Cause: Vibrations, loose components, worn-out bearings.
  • Solution: Secure all components and dampen vibrations. Replace worn-out bearings or other moving parts.
• Condensation Issues:
  • Possible Cause: Inadequate air drying, low ambient temperatures.
  • Solution: Ensure the compressed air dryer is functioning correctly. Insulate the generator and piping to prevent condensation.

Safety Considerations for Membrane Nitrogen Generation

Operating a membrane nitrogen generator involves certain safety considerations:

• High Pressure: The system operates under high pressure. Ensure all components are rated for the operating pressure and that pressure relief valves are in place.
• Gas Leaks: Nitrogen is an inert gas and can displace oxygen, leading to asphyxiation in confined spaces. Ensure adequate ventilation and use a nitrogen gas detector in enclosed areas.
• Electrical Safety: The generator uses electrical components. Follow all electrical safety guidelines and ensure the system is properly grounded.
• Maintenance: Regular maintenance is essential for safe and reliable operation. Follow the manufacturer’s recommendations for maintenance schedules and procedures.
• Emergency Shutdown: Know the location of the emergency shutdown switch and how to use it in case of a malfunction.

Let Anglian Compressors Help Guide You

Choosing the right nitrogen generation technologies for your business isn’t easy. While there are key benefits to adopting a membrane generator over a PSA system, we can advise correctly for your specific needs.

This way, you’ll receive a best-in-class nitrogen generation system with excellent energy efficiency, using the smallest possible footprint.

Contact us below.

FAQ

What is the working principle of a membrane nitrogen generator?

The principles of membrane nitrogen generators rely on separating nitrogen from compressed air using hollow fibres. The fibres have tiny pores that allow oxygen and water vapour to pass through while keeping nitrogen in the main flow. A typical unit runs at 7–10 bar pressure. The membranes look like bundles of drinking straws packed into a metal housing.

The pre-filters need checking weekly to prevent oil contamination from reaching the membrane bundle.

How does membrane nitrogen generation compare to PSA systems?

PSA systems use carbon sieve beds that grab oxygen molecules while letting nitrogen pass. They switch between beds every few minutes. 

Membrane units take up less space, about 1.5 square metres for a standard 40 m³/hr unit compared to nearly 3 square metres for an equivalent PSA. PSA achieves higher purity (up to 99.999%) but costs more to run. 

What are the advantages of using a membrane nitrogen generator?

Membrane generators need less maintenance than cylinder deliveries or PSA.The membrane elements last 5 years if kept clean.

On-site generation means no more paperwork for gas deliveries or cylinder rental.

What factors affect the capacity of a membrane nitrogen generator?

The capacity of a membrane nitrogen generator is influenced by several factors, including the inlet air pressure, temperature, and the type of membrane used. Higher inlet pressures generally lead to increased nitrogen production. The required nitrogen purity also affects capacity; higher purity levels typically result in a lower flow rate.

What is the typical lifespan of a membrane in a nitrogen generator?

The lifespan of a membrane in a nitrogen generator typically ranges from 5 to 10 years, depending on the operating conditions and the quality of the pre-filtration system. Proper maintenance and regular filter replacements can significantly extend the membrane’s lifespan.

What industries benefit most from using membrane nitrogen generators?

Industries that require a consistent and reliable supply of nitrogen, such as food packaging, pharmaceuticals, electronics manufacturing, and chemical processing, benefit most from using membrane nitrogen generators. These systems offer cost savings, improved control over nitrogen purity, and reduced reliance on external suppliers.