Interesting Facts and Information

Oxygen (O2):

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: -297.3F (-183C). 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 O2, oxygen may be referred to as GOX in its gaseous form, and LOX in its 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. It 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 through treatment of municipal and industrial effluents.  It 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, its even more reactive form, to enhance the rate of reaction and ensure full reaction with undesired compounds.


Nitrogen (N2):

Nitrogen (N2) is a colorless, odorless and tasteless gas that makes up 78.09% (by volume) of the air we breathe.  It is nonflammable and it will not support combustion. It is colorless, odorless and tasteless. 

Nitrogen gas is slightly lighter than air and slightly soluble in water.  It is commonly thought of and used as an inert gas; but it is not truly inert.  It forms nitric oxide and nitrogen dioxide with oxygen, ammonia with hydrogen, and nitrogen sulfide with sulfur.  Nitrogen compounds are formed naturally through biological activity.  Compounds are also formed at high temperature or at moderate temperature with the aid of catalysts. At high temperatures, nitrogen will combine with active metals, such as lithium, magnesium and titanium to form nitrides.  Nitrogen is necessary for various biological processes, and is used as a fertilizer, usually in the form of ammonia or ammonia-based compounds.  Compounds formed with halogens and certain organic compounds can be explosive. 

Nitrogen condenses at its boiling point, -195.8o C (-320.4o F), to a colorless liquid that is lighter than water. 

More nitrogen is used by customers than any other industrial gas.  It is used in a broad range of industries, including chemicals, pharmaceuticals, petroleum processing, glass and ceramic manufacture, steelmaking and other metals refining and fabrication processes, pulp and paper manufacture, and healthcare.  Aside from N2, nitrogen may be referred to as GAN or GN in its gaseous form, and LIN or LN in its liquid form.

Nitrogen is produced in large volumes in both gas and liquid form by cryogenic distillation; smaller volumes may be produced as a gas by pressure swing adsorption (PSA) or diffusion separation processes  (permeation through specially designed hollow fibers).  Cryogenic processes can produce very pure nitrogen.  Adsorption and diffusion processes are typically used to make lower purity product in relatively small amounts.  This is attractive to users when purity is not critical and alternatives (purchase of bulk liquid nitrogen, cylinders of high pressure nitrogen, or local cryogenic production) are more expensive or impractical. 

Gaseous nitrogen is valued for inertness.  It is used to shield potentially reactive materials from contact with oxygen.

Liquid nitrogen is valued for coldness as well as inertness.  When liquid nitrogen is vaporized and warmed to ambient temperature, it absorbs a large quantity  of heat.  The combination of inertness and its intensely cold initial state makes liquid nitrogen an ideal coolant for certain applications such as food freezing.  Liquid nitrogen is also used to cool materials which are heat sensitive or normally soft to allow machining or fracturing.  Examples are used tires, plastics, certain metals and even pharmaceuticals.

Carbon Dioxide (CO2):

Carbon dioxide (CO2) is a slightly toxic, odorless, colorless gas with a slightly pungent, acid taste.  Carbon dioxide is a small but important constituent of air.  It is a necessary raw material for most plants, which remove carbon dioxide from air using the process of photosynthesis. 

A typical concentration of CO2 in air is about 0.038% or 380 ppm. The concentration of atmospheric carbon dioxide rises and falls in a seasonal pattern over a range of about 6 ppmv. The concentration of CO2 in air has also been steadily increasing from year to year for over 60 years.  The current rate of increase is about 2 ppm per year.

Carbon dioxide is formed by combustion and by biological processes. These include decomposition of organic material, fermentation and digestion. As an example, exhaled air contains as much as 4% carbon dioxide, or about 100 times the amount of carbon dioxide which was breathed in.

Large quantities of CO2 are produced by lime kilns, which burn limestone (primarily calcium carbonate) to produce calcium oxide ( lime, used to make cement); and in the production of magnesium from dolomite (calcium magnesium carbonate).  Other industrial activities which produce large amounts of carbon dioxide are ammonia production and hydrogen production from natural gas or other hydrocarbon raw materials. 

The concentration of CO2 in air and in stack gases from simple combustion sources (heaters, boilers, furnaces) is not high enough to make carbon dioxide recovery commercially feasible.  Producing carbon dioxide as a commercial product requires that it be recovered and purified from a relatively high-volume, CO2-rich gas stream, generally a stream which is created as an unavoidable byproduct of a large-scale chemical production process or some form of biological process. 

In almost all cases, carbon dioxide which is captured and purified for commercial applications would be vented to the atmosphere at the production point if it was not recoved for transport and beneficial use at other locations. 

The most common operations from which commercially-produced carbon dioxide is recovered are industrial plants which produce hydrogen or ammonia from natural gas, coal, or other hydrocarbon feedstock, and large-volume fermentation operations in which plant products are made into ethanol for human consumption, automotive fuel or industrial use.  Breweries producing beer from various grain products are a traditional source.  Corn-to-ethanol plants have been the most rapidly growing source of feed gas for CO2 recovery. 

CO2-rich natural gas reservoirs found in underground formations found primarily in the western United States and in Canada are another source of recoverable carbon dioxide.  CO2 from both natural and industrial sources is used to enhance production of oil from older wells by injecting the carbon dioxide into appropriate underground formations.  Carbon dioxide is used in selectively, primarily in wells which will benefit not only from re-pressurization, but also from a reduction in viscosity of the oil in the reservoir caused by a portion of the CO2 dissolving in the oil.  (The extent to which carbon dioxide will dissolve in the oil varies with the type of petroleum present in the reservoir.  If the viscosity reduction effect will be minimal, nitrogen, which is usually less expensive, may be used as the pressurant instead.)

Carbon dioxide will not burn or support combustion.  Air with a carbon dioxide content of more than 10% will extinguish an open flame, and, if breathed, can be life-threatening.  Such concentrations may build up in silos, digestion chambers, wells, sewers and the like. Caution must be exercised when entering these types of confined spaces.

CO2 gas is 1.5 times as heavy as air, thus if released to the air it will concentrate at low elevations. Carbon dioxide will form "dry ice" at -78.5C (-109.3 F).  One kg of dry ice has the cooling capacity of 2 kg of ordinary ice.  Gaseous or liquid carbon dioxide, stored under pressure, will form dry ice through an auto-refrigeration process if rapidly depressured.

Carbon dioxide is commercially available as high pressure cylinder gas, relatively low pressure (about 300 psig or 20 barg) refrigerated liquid, or as dry ice. Large quantities are produced and consumed at industrial sites making fertilizers, plastics and rubber.

Carbon dioxide is a versatile material, being used in many processes and applications - each of which takes advantage of one or more these characteristics:  reactivity, inertness and/ or coldness

Carbon dioxide is commonly used as a raw material for production of various chemicals; as a working material in fire extinguishing systems; for carbonation of soft drinks; for freezing of food products such as poultry, meats, vegetables and fruit; for chilling of meats prior to grinding; for refrigeration and maintenance of ideal atmospheric conditions during transportation of food products to market; for enhancement of oil recovery from oil wells; and for treatment of alkaline water.

Carbon dioxide in air is considered to be a greenhouse gas because of its ability to absorb infrared light.

The concentration of CO2 in the Earth's atmosphere has been increasing at a noticeable rate for much of the past century, There is much interest and concern over the inter-relationship between the levels of carbon dioxide in air and the subject of global warming,

Carbon dioxide plays a major role as a component of the carbon cycle in which carbon is exchanged between the atmosphere, the terrestrial biosphere (which includes freshwater systems and soil), the oceans, and sediments (including fossil fuels). These interactions are complex and widespread.  They undoubtedly can be, and are, influenced by many types of human activities, but the extent to which humans have impacted these processes, and will impact them in the future, remains the subject of much research and debate.

Argon (Ar):

Argon (Ar) is a monatomic, colorless, odorless, tasteless and nontoxic gas, present in the atmosphere at a concentration of just under 1% (0.934%) by volume.  Argon is a member of a special group of gases known as the rare, noble, or inert gases.  Other gases in this group are helium, neon, krypton, xenon and radon.  They are monatomic gases with a totally filled outermost shell of electrons.  The terms "noble" and "inert" have been used to indicate that their ability to chemically interact with other materials is extremely weak.  All members of this group emit light when electrically excited.  Argon produces a pale blue-violet light. 

Argon's normal boiling point is a very cold  302.6F (185.9C). The gas is approximately 1.4 times as heavy as air and is slightly soluble in water. Argon's freezing point is only a few degrees lower than its normal boiling point, 308.8F (199.3C). 

Argon is valued for its total inertness, in particular at high temperatures.  Argon is used in critical industrial processes such as the manufacturing of high quality stainless steels and production of impurity-free silicon crystals for semi-conductor manufacture.  Argon is also used as an inert filler gas for light bulbs and as a dry, heavier-than-air-or-nitrogen filler for the space between glass panels in high-efficiency multi-pane windows.

Argon is the most abundant of the truly inert or "rare" gases.  It is produced, most commonly, in conjunction with the manufacture of high purity oxygen using cryogenic distillation of air.  Since the boiling point of argon is very close to that of oxygen (a difference of only 5.3F or 2.9C) separating pure argon from oxygen (while also achieving high recovery of both products) requires many stages of distillation.

         For many decades, the most common argon recovery and purification process used several steps: 1) taking a "side-draw" stream from the primary air separation distillation system at a point in the low-pressure column where the concentration of argon is highest, 2) processing the feed in a crude argon column which  returns the nitrogen to the low pressure column and produces a crude argon product, 3) warming the crude argon and reacting the (typically about 2%) oxygen impurity in the stream with a controlled amount of hydrogen to form water, 4) removing the water vapor by condensation and adsorption, 5) re-cooling the gas to cryogenic temperature, and 6) removing the remaining non-argon components (small amounts of nitrogen and unconsumed hydrogen) through further distillation in a pure argon distillation column. 

         With the development of packed column technology, which allows cryogenic distillations to be performed with low-pressure-drop, most new plants now utilize an all-cryogenic distillation process for argon recovery and purification.

Argon may be referred to as "PLAR" (pure liquid argon) or "CLAR" (crude liquid argon), or by its chemical designation, "Ar".   Crude argon is usually thought of as an intermediate product in a facility that makes pure argon, but it may be a final product for some lower capacity air separation plants which ship it to larger facilities for final purification.  Some crude argon is also sold as a final product for uses that do not need high purity oxygen (e.g. some steelmaking and welding applications). 

Commercial quantities of argon may also be produced in conjunction with the manufacture of ammonia.  Air is the ultimate source of the argon, but in the traditional ammonia production process the route to argon recovery is quite different. Natural gas is "reformed" with steam to produce a "synthesis gas" containing hydrogen, carbon monoxide and carbon dioxide.  "Secondary reforming" with air and steam converts the CO to CO2 and additional hydrogen, and adds the nitrogen necessary to make ammonia (NH3).  The mix of nitrogen and hydrogen (along with a small amount of argon) is then compressed to high pressure and reacted with the aid of a catalyst.  Argon, being non-reactive, accumulates in the ammonia synthesis loop, and it must be removed in a purge stream to maintain production capacity and process efficiency.  UIG offers equipment to process the purge gas stream.   Ammonia is removed and recovered while the hydrogen is removed and recycled to the synthesis gas feed to the ammonia process to improve overall process efficiency.  Methane, which is formed in the ammonia process, is recycled to fuel for the fired heater providing heat to drive the synthesis gas generation process.  Argon is recovered and purified for sale as a commercial product. 

Some newer ammonia plants do not use air as a direct feed to the ammonia production process, but process it through an air separation unit, with the argon removed upstream of the ammonia synthesis loop.  The high purity oxygen and nitrogen feed streams produced by the air separation unit are individually fed to the hydrogen production and ammonia production portions of the ammonia plant.  This newer ammonia production approach avoids argon buildup in the ammonia synthesis loop, and allows direct recovery of argon as a valuable co-product.



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