Oxygen (O2) is an active, life-sustaining component of the atmosphere; making up 20.94% by volume or 23% by weight of the air we breathe. It is colorless, odorless and tasteless.
Oxygen is the most widely occurring element on Earth. Because it forms compounds with virtually all chemical elements except the noble gases, most terrestrial oxygen is bound with other elements in compounds such as silicates, oxides, and water. Oxygen is also dissolved in rivers, lakes, and oceans. Molecular oxygen occurs almost entirely in the atmosphere.
Oxygen is highly oxidizing (a general chemical term applying to any substance, like oxygen, that accepts electrons from another substance during reaction). Oxygen reacts vigorously with combustible materials, especially in its pure state, releasing heat in the reaction process. Many reactions require the presence of water or are accelerated by a catalyst.
Ozone (O3) is an allotropic form of oxygen that is more reactive than ordinary oxygen. Ozone is formed in nature by electrical discharges or by irradiation with ultraviolet light. Commercial ozone generators mimic these natural process to make large amounts for industrial and environmental treatment processes or add a small amount of ozone to breathing air for its invigorating effect and "fresh air" scent.
Oxygen has a low boiling/ condensing point: -297.3°F (-183°C). The gas is approximately 1.1 times heavier than air and is slightly soluble in water and alcohol. Below its boiling point, oxygen is a pale blue liquid slightly heavier than water.
Oxygen is the second-largest volume industrial gas. Aside from its chemical name O2, oxygen may be referred to as GOX or GO when produced and delivered in gaseous form, or as LOX or LO when in its cryogenic liquid form.
Oxygen is produced in large quantities and at high purity as a gas or liquid by cryogenic distillation and as a lower purity gas (typically about 93%) by adsorption technologies (pressure swing adsorption, abbreviated as PSA, or vacuum-pressure swing adsorption, abbreviated as VPSA or more simply, VSA).
Oxygen is valued for its reactivity. Oxygen is commonly used, with or instead of air, to increase the amount of oxygen available for combustion or biological activity. This increases reaction rates and leads to greater throughput in existing equipment and smaller sizes for new equipment.
Oxygen has numerous uses in steelmaking and other metals refining and fabrication processes, in chemicals, pharmaceuticals, petroleum processing, glass and ceramic manufacture, and pulp and paper manufacture. It is used for environmental protection in municipal and industrial effluent treatment plants and facilities. Oxygen has numerous uses in healthcare, both in hospitals, outpatient treatment centers and home use. For some uses, such as effluent treatment and pulp and paper bleaching, oxygen is converted to ozone (O3), an even more reactive form, to enhance the rate of reaction and to ensure the fullest possible oxidation of undesired compounds.
English Units |
Normal Boiling Point (1 atm) | Gas Phase Properties @ 32°F & @1 atm | Liquid Phase Properties @ B P& @ 1 atm | Triple Point | Critical Point | |||||||||
| Temp. | Latent Heat of Vaporization | Specific Gravity | Specific Heat (Cp) | Density | Specific Gravity | Specific Heat (Cp) | Temp. | Pressure | Temp. | Pressure | Density | |||
| Substance | Chemical Symbol | Mol. Weight | ° F | BTU/lb | Air = 1 | BTU/lb °F | lb/cu. ft | Water = 1 | BTU/lb °F | °F | psia | °F | psia | lb/cu ft |
| Oxygen | O2 | 32.00 | -297.3 | 91.7 | 1.113 | 0.2197 | 0.089212 | 1.14 | 0.4058 | -361.8 | 0.02147 | -181.43 | 731.4 | 27.22 |
Metric Units |
Boiling Point @ 101.325 kPa | Gas Phase Properties @ 0° C & @ 101.325 kPa | Liquid Phase Properties @ B.P., & @ 101.325 kPa | Triple Point | Critical Point | |||||||||
| Temp. | Latent Heat of Vaporization | Specific Gravity | Specific Heat (Cp) | Density | Specific Gravity | Specific Heat (Cp) | Temp. | Pressure | Temp. | Pressure | Density | |||
| Substance | Chemical Symbol | Mol. Weight | °C | kJ/kg | Air = 1 | kJ/kg ° C | kg/m3 | Water = 1 | kJ/kg ° C | °C | kPa abs | ° C | kPa abs | kg/m3 |
| Oxygen | O2 | 32.00 | -182.96 | 213.0 | 1.113 | 0.9191 | 1.429 | 1.14 | 1.669 | -218.8 | 0.148 | -188.57 | 5043 | 436.1 |
Oxygen is used with fuel gases in gas welding, gas cutting, oxygen scarfing, flame cleaning, flame hardening, and flame straightening.
In gas cutting, the oxygen must be of high quality to ensure a high cutting speed and a clean cut.
The largest user of oxygen is the steel industry. Modern steelmaking relies heavily on the use of oxygen to enrich air and increase combustion temperatures in blast furnaces and open hearth furnaces as well as to replace coke with other combustible materials. During the steel making process, unwanted carbon combines with oxygen to form carbon oxides, which leave as gases. Oxygen is fed into the steel bath through a special lance. Oxygen is used to allow greater use of scrap metal in electric arc furnaces. Large quantities of oxygen are also used to make other metals, such as copper, lead, and zinc.
Oxygen enrichment of combustion air, or oxygen injection through lances, is used to an increasing extent in cupola furnaces, open-hearth furnaces, smelters for glass and mineral wool, and lime and cement kilns, to enhance their capacity and reduce energy requirements. Smelting times and energy consumption can also be reduced by special oxy-oil or oxy-gas burners in electro-steel furnaces and induction smelters for aluminum. A high thermal efficiency is achieved by these “oxy-fuel” burners, which mix fuel and oxygen at the tip of the burner. As a result, rapid combustion occurs at approximately 2800o C (5072oF).
Oxygen is used as a raw material in many oxidation processes, including the manufacture of ethylene oxide, propylene oxide, synthesis gas using partial oxidation of a wide range of hydrocarbons, ethylene dichloride, hydrogen peroxide, nitric acid, vinyl chloride and phthalic acid.
Very large quantities of oxygen are used in coal gasification — to generate a synthesis gas that can be used as a chemical feedstock or precursor for more easily- transported and easily-used fuels.
Oxygen is used to enrich the air feed to catalytic cracking regenerators, which increases capacity of the units. It is used in sulfur recovery units to achieve similar benefits. Oxygen is also used to regenerate catalysts in refineries.
Oxygen is used to achieve more complete combustion and destruction of hazardous and waste materials in incinerators.
Conversion of combustion systems from air-fuel to oxy-fuel (and construction of new furnaces and tanks around this technology) results in better control of heating patterns, higher furnace efficiencies (lower fuel consumption) and reduction in particulate and NOx emissions.
Oxygen is increasingly important as a bleaching chemical. In the manufacture of high-quality bleached pulp, the lignin in the pulp must be removed in a bleaching process. Chlorine has been used for this purpose but new processes using oxygen reduce water pollution. Oxygen plus caustic soda can replace hypochlorite and chlorine dioxide in the bleaching process, resulting in lower costs.
In a chemical pulp mill, oxygen added to the combustion air increases the production capacity of the soda recovery boiler and the lime-reburning kiln. The use of oxygen in black liquor oxidation reduces the discharge of sulfur pollutants into the atmosphere.
In medicine, oxygen is used during surgery, intensive care treatment, inhalation therapy, etc. High standards of purity and handling must be maintained.
Oxygen is typically supplied to hospitals though bulk liquid deliveries, then distributed to usage points. It assists with respiratory problems, saving lives and increasing patient comfort.
Small portable air separation units are gaining wide use in home care. Larger scale units using which also use non-cryogenic air separation technology, are being utilized in small and/or remote hospitals where demand is high enough to make cylinder deliveries a logistical problem but where liquid deliveries are unavailable or very costly. These units typically producing 90 to 93% purity oxygen, which is adequate for most medical uses.
In the biological treatment of waste-water, the use of oxygen instead of air permits increased capacity in existing treatment plants. Injecting oxygen into sewers reduces hydrogen sulfide formation, which results in reduced corrosion and odor.
Ozone is used for drinking water treatment, in particular when alternatives, such as chlorine, are undesirable.
Oxygen has many uses in breathing apparatus, such as those for underwater work and refinery and chemical plant self contained breathing apparatus.
Aquaculture, the cultivation of fish in ponds uses oxygenated water to allow ensure sufficient oxygen is always present and to allow more fish to be raised or kept in a given size of pond or tank.
Liquid oxygen is used in liquid-fueled rockets as the oxidizer for fuels such as hydrogen and liquid methane