Nitrogen is an element, which exists as a gas in its natural state at normal pressure and temperature. Nitrogen makes up approximately 78% of the air we breathe. Nitrogen is an inert gas, which means that it does not react readily with other elements, and does not burn or support combustion. In the chemical and gas industries, Nitrogen is used to provide an inert atmosphere over reactive processes that would burn or explode if exposed to Oxygen in the air. Gaseous Nitrogen is colorless, odorless and tasteless.
The primary hazard of gaseous Nitrogen is that it can displace the Oxygen in the air and create an Oxygen deficient atmosphere that can cause asphyxiation. The signs of Oxygen deficiency begin to occur at 14% to 16% Oxygen in the air with an increased rate and depth of breathing. If the Oxygen content in the air falls to 4% or less, unconsciousness can occur after only one or two breaths. The Oxygen content in the air must be between 19.5% and 22.0% for personnel to enter a confined space.
Liquid Nitrogen is colorless and odorless, is lighter than water (Density 808.29 Kg /m3), and has a boiling point of -320oF (-196oC) at atmospheric pressure. It is transported and stored as a liquid for economy and convenience. One cubic foot of liquid Nitrogen will expand to 696 cubic feet of gas at the same pressure. Rapid release of nitrogen gas into an enclosed space can displace oxygen, and therefore presents an asphyxiation hazard. This may happen with few warning symptoms, since the human carotid body is a relatively slow and a poor low-oxygen (hypoxia) sensing system.
Nitrogen also dissolves in the bloodstream and body fats.
As with all cryogenic liquids, exposure to the liquid or piping can cause frostbite and cold burn. This may happen almost instantly on contact, or after a second or more, depending on the form of liquid nitrogen. Bulk liquid nitrogen causes less rapid freezing than a spray of nitrogen mist (such as is used to freeze certain skin growths in the practice of dermatology).
Oxygen sensors are sometimes used as a safety precaution when working with liquid nitrogen to alert workers of gas spills into a confined space.
IS 1747: 1972
The cylinders are available in 7 m3 capacity and 150 kg/cm2 pressure, 11m3 at 200 kg/cm2 and 12 m3 at 200 kg/cm2 Portable cryogenic containers
Inert properties of nitrogen make it a good “ blanketing gas ”(A gas phase introduced above a liquid or solid phase to prevent oxidation, contamination, fire, degradation, reduce hazard of detonation).Hence certain chemicals, solids, and food products are kept in a Nitrogen atmosphere.”Inerting” and “padding” are other terms used to describe displacement of air and nitrogen blanketing.
”Sparging” (spraying) with N2 is used to remove unwanted volatile components and volatile organic compounds (VOC) to meet pollution reduction regulations.
LN is used to freeze soft or tough substances.
Cold vaporized N2 can be used to keep materials cool during grinding.”Cryogenic grinding” is used in diverse applications, including production of finely ground pharmaceuticals, plastics and pigments, and for shredding (cut into fine particles) tires in recycling plants.
N2 is used to treat the melt in the manufacture of steel and other metals and as a shield gas to protect metals such as Steel, Copper and Aluminium during annealing, carburizing and sintering operations in high temperature furnaces.
”Flash” or”fins” on cast metal can be removed by cooling with N2; making them brittle and allowing then to be broken off by mechanical action.
During manufacturing process, shrink fitting is an useful alternative to traditional expansion fitting.
LN is used to cool concrete for better cured properties (flexibility, high strength etc.).
LN is used for soil-freezing and thus stabilization of ground for tunneling, shaft sinking etc.
Refineries and petrochemical plants and marine tankers use N2 to purge equipment, tanks and pipelines of dangerous vapours, gases and flammable
Regeneration of purification beds (Molecular sieve and Alumina).
Preparation of catalysts and transportation of polymer powders.
Medium for the exit of emitted heat in fluid bed reactors.
To cool reactors filled with catalyst during maintenance work and temperature control in reactors.
Recovery of high value volatile material by condensation.
Low temperatures in cooling reactors allow better control of side-reactions.
N2 is used for inerting, cryogenic grinding, Lyophilization (method of drying food or blood plasma or pharmaceuticals or tissue without destroying their physical structure),
N2 is used for drying, liquid phase transfer of products or synthesis intermediates.
N2 is used for Cryo-condensation of waste gases and low temperature storage and transportation of vaccines.
Rubber and plastic materials become hard and brittle when cooled. This property permits the removal of “flash” or “fins” on cast plastics and rubber, also used for “blow moulding” (process by which hollow plastic parts are formed).
LN is the most used cryogenic fluid, to chill, freeze or store food products.
Sparging with N2 reduces dissolved oxygen (DO) level in liquids like fruit juices, beer, edible oil etc.
O2 elimination reduces rancidity, vitamin loss, loss of flavor/color, oxidation of protein pigment, microbial growth, insect infestation (presence of large no. of pest organisms) and moisture migration and used in modified atmosphere packaging (MAP).
Storage/ preservation of blood, tissues, vaccines, viruses, livestock semen at controlled low temperature and also for transportation.
Nitrogen is used in MRI (Magnetic Resonance Imaging) devices.
Liquid Nitrogen is used to attain low temperature for cryo-surgery.
N2 is used as carrier gas in gas chromatography.
Balance gas of the calibration gas mixtures for industrial hygiene gas mixtures and environmental monitoring systems.
N2 flushing in underground colliery to control spontaneous heating and fire by inertisation process (Fire control).
Pneumatic transportation of powdered flammable materials like charcoal can be done by using N2.
N2 is used for secondary steel making (inert gas with O2 to control carbon), continuous casting and degassing operations of molten metal.
Atomizing metal stream by N2 to produce powder metal for forging (shaping), sintering and hot isostatic pressing.
N2 is used as carrier gas in semiconductors manufacturing and soldering processes.
LN is used as cooling medium in the environmental testing of electronic devices.
99.9999% N2 is required in the process of micro-electronic component manufacture and carrier gas for dopants.
N2 based controlled furnace atmosphere for annealing, malleabilising, carburizing, normalizing and hardening of metal.
N2 is used for purging (purifying), blanketing, fire prevention and oil well stimulation/ enhanced oil recovery. Unlike CO2, N2 has little affinity for liquid hydrocarbons, so it is used for pressurization.
N2 is used for flushing shells before specific gas/gas mixture filling.
LN is used for hot/cold cyclic testing of components, equipment and complete vehicle.
Tires filled with N2 increases their lifetime, thus decreases the recycling or treatment of this waste.
N2 is used to cool furnace electrodes in the production process of glass.
Nitrogen is used in “technical scuba diving (SCUBA-Self Contained Underwater Breathing Apparatus)”
N2/H2 protective atmosphere is used for tin bath in glass sheet production by float method (float glass).