Nitrogen is a diatomic gas which comprises 78 percent of the earth's atmosphere.
In addition to air, nitrogen is found in the protein matter of all life forms, in some natural gas-hydrocarbon deposits, and in many organic and inorganic compounds.
Chemical formula: N2
Purity level: ≥ 99.9%
Relative density (air = 1): 0.97
Aspect: colourless gas
Odour: odourless gas
Limit of flammability in air: not flammable
Other properties: nontoxic, only slightly soluble in water and most other liquids, poor conductor of heat and electricity, inert. However at high temperatures and pressures, it will combine with some reactive metals (such as lithium and magnesium) to form nitrides, as well as with some gaseous elements such as hydrogen and oxygen.
Nitrogen is used in several applications, which are listed below.
In the chemical industry, nitrogen is used:
- to inert vessels and oxygen-sensitive chemicals, creating an oxygen-deficient environment which reduces safety hazards
- to propel liquids through pipelines
- to manufacture ammonia.
In the food industry, nitrogen is used:
- to extend shelf-life in packaged foods by preventing spoilage from oxidation, mould growth, moisture migration and insect infestation
- to thermoregulate and cool food
- to rapidly freeze (cryogenic freezing and IQF) food
- for stripping gases from liquids
- for pneumatic transport of ingredients and to render food storage tanks inert
- to refrigerate perishables during transport
- for modified atmosphere packaging
- for food cryo-grinding and cryo-crystallization
- to deodorize oils.
In the petroleum industry, nitrogen is used:
- to improve recovery and maintain pressure in oil and gas reservoirs
- to blanket storage tanks and product loading/unloading
- to purge pipelines
- to strip volatile organic compounds (VOCs) from waste streams or to cool vent streams.
In metal production, nitrogen is used:
- to protect metals such as steel, copper and aluminum during annealing, carburizing and sintering operations in high temperature furnaces
- to cool extrusion dyes
- to shrink fit metal parts.
In metal fabrication, nitrogen is used:
- as a purge gas with stainless steel tube welding
- to support plasma cutting
- to prevent oxidation in the manufacture of semiconductors and printed circuits.
In the electronics industry, nitrogen is used:
- to enhance solvent recovery systems by eliminating the use of chlorofluorocarbons for cleanup.
In the glass industry, nitrogen is used:
- to cool furnace electrodes and prevent oxidation during manufacturing
- to lower air temperatures for optimum cooling rates.
Research and health services
In research and health services, nitrogen is used:
- to freeze and preserve blood, tissue, semen and other biological specimens
- to freeze and destroy diseased tissue in cryosurgery and dermatology
- to pre-cool or insulate Magnetic Resonance Imaging (MRI), conserving the more costly helium.
In construction, nitrogen is used:
- to suppress the pour temperature of concrete mixtures, inhibiting the formation of cracks
- to stabilize the ground as in the restoration of the Leaning Tower of Pisa.
Nitrogen, one of the largest volume industrial gases, is produced commercially by the air separation process.
This process consists of separating the components contained in air:
- nitrogen(78 %)
- oxygen (21 %)
- argon (0,9 %)
- other gases (0,1 %).
Present day plants represent the evolution of the Claude-Linde process named after the French and German scientists who contributed to their development; for air cooling they initially adopted isoenthalpic expansion, just with pressure drop, and later isoentropic expansion, with energy production.
The plant consists of two columns, one above the other, operating at different pressures and with gas flow (rising) and liquid flow (descending) in equilibrium between the gas and liquid phases. As one gets towards the top of the column there is an increasing concentration of nitrogen and towards the bottom an increasing concentration of oxygen.
Argon is obtained in a third fractionation column, in which the distillation process is repeated on an oxygen-argon mixture taken from an intermediate point of the upper column. Present day air separation plants have reached a high degree of automation and their control is carried out via a computer; the control system handles the entire production cycle and the following phase of product distribution through to storage or utilisation.
In the Osio Sopra production plant, Italy's most state-of-the-art plant in the field of Industrial Gases and the biggest of SIAD's production units, the new air separation plant T 1000, which went live in September 1997 and replaced part of the older plants, assures a production capacity on site of 1300 tons of oxygen per day.
The plant was designed by SIAD MACCHINE IMPIANTI.
Nitrogen supply options and services available to SIAD customers include:
- transport in cylinders, cylinder packs or tanks
- design and installation of gas distribution systems
- supply of equipment for the correct use of the gas
- assistance and technical consultancy for the transport, distribution and application of the gas.
Nitrogen can also be supplied:
- with grades 4.7 - 5.0 - 6.0 purity
- in special and in calibration mixtures with different compositions upon request
- in synthetic air.