What is an Oxygen Generator?
Oxygen generators separate oxygen from air so that the gas can be fed into industrial processes in real-time or stored in pressure tanks. Oxygen generators are used in dozens of industrial applications ranging from gold mining to aquaculture to life support.
Normal ambient air is made up of 78% nitrogen, 21% oxygen and other trace gases like argon and CO2. In order to remove the nitrogen and trace gases, an oxygen generator is used.
The smallest oxygen generators are no larger than a soda can, while industrial oxygen generators can fill a room. However, all oxygen generators have the same purpose: to provide a safe supply of concentrated oxygen gas.
Businesses who need bulk oxygen gas often start by purchasing tanks of the gas from other companies who fill those tanks using an industrial oxygen generator. If their need for pure oxygen is large and ongoing, it may be cost-effective to purchase their own oxygen generator system and produce oxygen on site. While the up-front cost of the machinery is significant, the cost per cubic foot of oxygen generated is 1/3 to 1/2 that of purchasing bulk oxygen, so over time, the oxygen generator can pay for itself.
One example of this is hospitals that pipe oxygen into patient rooms.
Types of Oxygen Generators
Pressure Swing Adsorption Oxygen Generator
Pressure Swing Adsorption (PSA) is the most common method of producing oxygen at an industrial scale. PSA generators separate nitrogen from ambient air inside a pressurized tank filled with Zeolite. Zeolite is a natural or man-made mineral that acts as a “molecular sieve.” It is this ability to “sort” molecules by size that makes zeolite so useful. The larger nitrogen molecules are adsorbed by the sieve material while the smaller oxygen molecules drift past and are collected. Pressure is then released, the nitrogen molecules are vented to the atmosphere, and the tank is pressurized again.
Using PSA will result in 90-95% oxygenated gas. Further refinement can be achieved by repeating the process until over 99% “pure” oxygen is generated.
As a side note, the PSA process can also be used to generate nitrogen by collecting the nitrogen molecules and venting the oxygen. PSA is also used in the large-scale commercial synthesis of hydrogen used in oil refineries and in the production of ammonia for fertilizer.
One special kind of oxygen generator is more commonly known as an oxygen concentrator which is used as an alternative to oxygen bottles for home health care. While the up-front cost of the machine is more expensive than oxygen cylinders, they are safer than bottled oxygen and over time less expensive than having oxygen tanks delivered to the home.
Oxygen concentrators are normally sold through medical supply houses and can be purchased with a prescription from a physician.
Membrane Oxygen Generator
Membrane oxygen generators us a compressed air stream passed through semi-permeable materials that allow for the passage of specific molecules. Under pressure, smaller oxygen molecules pass through the membrane, filtered out and collected leaving a stream of nitrogen flowing out the opposite end of the membrane. While membrane-type generators are not as common, they are considered to be more reliable because there are no moving parts that can fail.
Chemical Oxygen Generator (oxygen in airplane)
A chemical oxygen generator is a device that releases oxygen by a chemical reaction. A container of inorganic salts called “superoxides” or sodium chlorate are ignited. As they heat they give off oxygen until the compound is consumed.
Because of their long shelf-life, stability and small size (about the size of a can of soda) chemical oxygen generators are used in commercial airliners. Mounted over the seats, each generator can produce enough oxygen for 2-3 masks for 10-20 minutes. A similar device is called an oxygen candle. It works using the same principle of releasing oxygen with heat, and is used as a personal safety oxygen supply in mines, submarines and on the space station.
Oxygen Generator Uses
While there are dozens of uses for industrial oxygen generators, some of the most common ones are listed below.
Medical Grade Oxygen
Medical grade oxygen used in hospitals or for home health care is certified to meet the United States Pharmacopeia (USP) XXII Oxygen 93% Monograph. USP requirements are the oxygen level is between 90 and 96% pure with the remainder made up of argon and hydrogen. No more than 300ppm of CO2 or any other gases or molecules are allowed.
The International Space Station, submarines and SCUBA divers all rely on oxygen generators to produce breathable air. Because they are closed systems, each work in conjunction with carbon dioxide “scrubbers” to remove the CO2 while bringing the oxygen level back to 20.9% oxygenated air.
Fish farms & Aquaculture
Like humans, fish and other marine animals required oxygen to survive. With the prevalence of fish farms, the “farmers” must insure their livestock gets proper oxygen to survive. Before fish farming was done on an industrial scale, the farmers would fence off an area of water at the edge of a lake to raise their catch. With industrial oxygen generators, farmers now have the ability to raise fish in man-made pools of oxygenated water. The benefit to the farmer is higher stock densities in a smaller area and faster fish growth.
Sewage and Waste Water treatment
In waste water treatment plants oxygen generators are used to provide additional oxygen to the bacteria that enable biodegradation to occur. The bacteria break down the sludge into CO2 and water faster if supplemental oxygen is added during the process.
Industrial oxygen generators are used in the steel manufacturing process in several ways. Oxygen furnaces are used for decarburization, the process of decreasing the carbon in the metals while in a molten state. Oxygen is also used to increase the melting rates in the furnaces and reduces scaling when reheating furnaces.
Mines that extract gold on an industrial scale use oxygen generators during the cyanide leaching process. A sodium-cyanide solution is mixed into crushed gold-bearing rocks along with oxygen to release the gold from the rock.
Oxy-acetylene cutting and welding of metals use liquid fuel and oxygen to increase the flame temperature so that the metal is melted at the point of the welding tip. This melting can be used to weld or to cut the metal.
Like welding, glass blowing requires high levels of heat to melt the glass. Oxygen is used to increase the temperature of the flames both in ovens and for torches used to shape the glass pieces.
Pulp and Paper Manufacturing
Delignification is the process of extracting lignin from the plant material in one of the steps required to make paper from trees. Large amounts of oxygen are required in this process, as well as several other later steps in pulp and paper manufacturing.