Nitrogen Compression

Nitrogen (N2) is a colorless, odorless and tasteless gas that constitutes 78.08% by volume of the air we breathe.  Nitrogen is an inert gas; the term inert basically means unreactive.  

Nitrogen occurs in all living organisms.  Nitrogen is a constituent element of amino acids and thus of proteins and nucleic acids (DNA and RNA). It resides in the chemical structure of almost all neurotransmitters, or in other words, nitrogen is an important chemical in the thinking process, and as you read this article you are utilizing nitrogen to connect cognitive thought patterns via synapses in your brain.

The bulk of nitrogen produced in the United States is done via cryogenic separation of air.  Air is supercooled to a liquid state, and the different gases stratify, just as water and oil do in a glass.  Nitrogen is then pulled out as a liquid.  Air separation plants can be large facilities serving multiple customers usually covering several states, or site specific for large users of nitrogen.  Cryogenic nitrogen purity can vary depending upon need, but can hold in the ppb (parts per billion) of contaminant gases.

A method of Nitrogen production gaining rapid favor for its ease of installation and relatively low cost are nitrogen generators that separate the nitrogen from air in the gaseous phase, either through the use of a membrane, or via pressure swing adsorption (similar to regenerative air dryers).  These units are fairly small in size and production volumes (roughly 100-10,000 scfh per system), but can be 1/10th to 1/100th the cost of a cryogenic separation plant.  However, gaseous nitrogen generators don’t produce pure nitrogen – they actually remove oxygen.  So while the oxygen content can reach less than 10ppm, there will still be other gases present in the nitrogen that are also present in air – gases like argon, helium, carbon dioxide, etc.  In many applications, this is acceptable, as the nitrogen is being used because oxygen cannot be present in the process.

Safety, Storage & Handling:

Nitrogen is commonly stored in high pressure cylinders, tubes or tube trailers.  Liquide nitrogen is commonly stored at the consumer site in cryogenic liquid cylinders and specifically designed vacuum-insulated storage tanks.  All of the precautions necessary for the handling of any nonflammable gas or cryogenic liquid must be taken.

If levels of nitrogen become too high in confined spaces it can cause asphyxiation, leading to unconsciousness or death. Therefore, all nitrogen compression equipment must be located in a well ventilated area.  We urge you to review local and regional safety standards to ensure safety compliancy.

To dispose of nitrogen gas, vent the N2 slowly to a well-ventilated outdoor location remote from personal work areas and building air intakes. For liquid nitrogen, allow it to evaporate in a similar location.  Liquid nitrogen boils at -320oF, so any temperature above that will be sufficient.      

Uses:

Nitrogen has many commercial and technical applications. As a gas, it is used in heat treating of primary metals; blanketing of oxygen-sensitive liquids and of volatile liquid chemicals; the production of semiconductor electronic components, as a blanketing atmosphere; the blowing of foam-type plastics; the deaeration of oxygen-sensitive liquids; the degassing of nonferrous metals; food processing and packing; inhibition of aerobic bacteria growth; magnesium reduction of aluminum scrap; and the propulsion of liquids through pipelines.

Gaseous nitrogen is also used in pressurizing aircraft tires and emergency bottles to operate landing gear; purging, in the brazing of copper tubing for air-conditioning and refrigeration systems; the purging and filling of electronic devices; the purging, filling, and testing of high-voltage compression cables; the purging and testing of pipelines and related instruments; and the treatment of alkyd resins in the paint industry.

Liquid nitrogen also has a great many uses, among them the freezing of highly perishable foods such as shrimp, hamburgers, and chicken; deflashing of rubber tires; cooling of concrete; and the cold-trapping of materials such as carbon dioxide from gas streams (commonly used in this way in systems that produce high vacuums).  It is used as a coolant for electronic equipment, for pulverizing plastics, and for simulating the conditions of outer space. Other ways in which liquid nitrogen is used include:  creating a very high pressure gaseous nitrogen (15,000 psig or 103,000 kPa) through liquid nitrogen pumping; in food and chemical pulverization; for the freezing of liquids in pipelines for emergency repairs; for low temperature stabilization and hardening of metals; for low temperature research; for low temperature stress relieving of aluminum alloys; for the preservation of whole blood, livestock sperm, and other biological; for refrigerating foods in local and long-distance hauling; for refrigeration shielding of liquid hydrogen, helium, and neon; for the removal of skin blemishes in dermatology; and for shrink fitting of metal parts.

Liquid nitrogen also has a number of classified applications in the missile and space programs, in which it is used in large quantities.

Reference the table below for common industries and applications using Nitrogen