Our junior high science classes taught us that nitrogen is everywhere . It’s in the air, in the ground, in plants and animals, and can get into water supplies. Nitrogen is one of the nutrients that plants and animals need for growth and nourishment. But it also has a long string of industrial and chemical uses in the modern world.
Nitrogen is necessary for agriculture, industry, and to sustain life. Having a readily available source of this gas when it’s needed is essential. How do we generate large quantities of pure nitrogen on demand? Nitrogen makes up 78 percent of Earth’s air. But you can’t just pull it out of the air, can you?
Actually, you can.
Enter air separation plants and nitrogen generators.
This type of industrial plant separates atmospheric air into its naturally occurring component gases. These plants harvest oxygen, nitrogen, argon, and some inert gases such as xenon, neon, and krypton.
The process used in air separation plants is cryogenic distillation. It is a four-step process that cools atmospheric air to extremely low temperatures. When cooled like this, the component gases are then isolated, separated, and collected. Some plants can also harvest the liquid forms of nitrogen or oxygen.
Air separation plants produce gases used in industrial processes. These gases are usually transported by direct pipelines or stored in liquid forms for transport via tanker trucks.
Various industries rely on nitrogen generators on-site to supply their nitrogen needs. The use of on-site nitrogen generators eliminates the problems frequently associated with traditional gas cylinders. It costs less to run a nitrogen generator on-site than using refillable gas cylinders.
There are two basic types of nitrogen generators: membrane and pressure swing absorption (PSA.) Both models are environmentally friendly and require very little maintenance once properly installed.
A membrane-based generator separates compressed air through semipermeable, hollow-fiber membranes. The normal oxygen and carbon dioxide found in the air get vented away while the nitrogen passes through the membrane.
With this type of nitrogen generator, a nitrogen purity rating from 95 percent to 99.5 percent is possible by raising the temperature while decreasing the airflow into the system.
When considering a membrane system, the total cost of ownership should figure in the decision. Using heat to enhance the membrane performance will increase the price of operation. The more highly permeable the membrane used, the more efficient and lower cost the system will likely be.
PSA generator systems use a combination of high- and low-pressure cycling. Oxygen-absorbing molecular sieves enrich the amount of nitrogen in the air from an average concentration of 78 percent to as high as 99.9 percent.
A PSA system may be mono-bed or dual-bed. The compressed air passes through the media at high pressure, selectively retaining the oxygen, and the nitrogen passes through until the media bed saturates. Rapid depressurization of the mono or dual bed releases the oxygen back into the atmosphere.
The mono-bed system is best for lower flow rates, while the dual-bed system is capable of higher flow rates by alternating between the two tanks.
A PSA system is more versatile than a membrane-based generator. These types of generators are suitable for many locales, from small to medium-sized laboratories to providing in-house nitrogen for large plants and industrial facilities.
Nitrogen is a vital component in many industrial markets and manufacturing facilities. Companies are always on the prowl for new problem-solving techniques and cost-saving measures that have a low-impact on current business practices. On-site nitrogen generation is growing in popularity as a solution to multiple business problems.