Oxygen storage

Methods of oxygen storage for subsequent use span many approaches, including high pressures in oxygen tanks, cryogenics, oxygen-rich compounds and reaction mixtures, and chemical compounds that reversibly release oxygen upon heating or pressure change. O2 is the second most important industrial gas.

Air

Air is the most common source and reservoir of oxygen, containing 20.8%[1] This concentration is sufficient for many purposes, such as combustion of many fuels, corrosion of many metals, and breathing of animals. Most humans can function at rest with an oxygen level of 15% at one atmosphere pressure;[2] a fuel such as methane is combustable down to 12% oxygen in nitrogen.[3]

A small room of 10 meter3 has 2.08 meter3 (2080 liters) or 2.99 kg of oxygen which would occupy 2.62 liters if it was liquid.[4]

High pressure

Oxygen tanks containing pressures up to 200 bar (3000 psi) are used for industrial processes including the manufacture of steel and monel, welding and cutting, medical breathing gas, diving and as emergency backup in aircraft.

A small steel tank of 16 liters water capacity with a working pressure of 139 bar (2015 psi) holds about 2150 liters of gas and weighs 28 kilograms (62 lb) empty.[5] 2150 liters of oxygen weighs about 3 kilograms (6.6 lb)

Cryogenic

Liquid oxygen in a cryogenic storage dewar (vacuum-insulated flask) is used in aerospace, submarine and gas industries.

Chemical oxygen generators

Chemical oxygen generators store oxygen in their chemical composition, and can be used only one time.

Oxygen Candles contain a mix of sodium chlorate and iron powder, which when ignited smolders at about 600 °C (1,112 °F) and results in sodium chloride, iron oxide, and oxygen, about 270 liters per kg of mixture.

Some commercial airliners use emergency oxygen generators containing a mixture of sodium chlorate (NaClO3), 5 percent barium peroxide (BaO2) and 1 percent potassium perchlorate (KClO4), which after ignition, reacts releasing oxygen for 12 to 22 minutes while the unit reaches 500 °F (260 °C).

The Vika oxygen generating system, used on Mir and later the International Space Station under the NASA designation Solid Fuel Oxygen Generator (SFOG) is based on lithium perchlorate, which releases about 60% of its weight in oxygen. Of all the perchlorates, lithium perchlorate has both the highest oxygen to weight and oxygen to volume ratio, except beryllium diperchlorate which is expensive and toxic. The Vika system uses a canister containing about 1 liter (2.4 kg) of perchlorate to generate 600 liters (0.86 kg) of oxygen, enough for one person for one day.[6]

Chemical oxygen generators containing potassium superoxide were used on the Soyuz spacecraft and in some mine safety Self-Contained Self-Rescue (SCSR) devices; KO2 reacts with both H2O and CO2 to produce oxygen, and 0.38 kg of oxygen is generated per kg of superoxide.

Tetramethylammonium ozonide ((CH3)4NO3) is proposed as a source of oxygen for generators because of its low molecular weight, being 39% oxygen.[7]

Reversible chemical absorbers

Scientists at the University of Southern Denmark published a paper on oxygen storage by chemisorption. Two molecules of dioxygen are stored into a crystalline salt {(bpbp)CoII2NO3}2(2-amino-1,4-benzenedicarboxylato)(NO3)2·2H2O. at 35 Celsius, and released by heating to 100 Celsius.[8] "Bpbp" is 2,6-bis(N,N-bis(2-pyridylmethyl)aminomethyl)-4-tert-butylphenolato.

An analogy of the function of cobalt bound to their organic molecule was made to the function of iron and copper in metalloproteins used for respiration by animals. The nitrate anions in the crystal are exchanged with neutral dioxygen but remain in the crystal; other anions besides nitrate work similarly and exchange oxygen faster. 10 liters of crystals are "enough to suck up all the oxygen in a room", three times more oxygen than an equivalent sized steel tank.[9]

See also

References

  1. ↑ oxygen
  2. ↑ http://www.newton.dep.anl.gov/askasci/zoo00/zoo00755.htm Oxygen and Human Requirements
  3. ↑ Limiting oxygen concentration
  4. ↑ 2 meter x 2 meter x 2.5 meter = 10 meter3 times concentration and density of Oxygen at STP
  5. ↑ http://www.alspecialtygases.com/Prd_high-pressure_steel.aspx High-Pressure Steel Compressed Gas Cylinder Sizes
  6. ↑ Vika oxygen generator
  7. ↑ http://www.google.com/patents/US3139327 U.S.Patent 3,139,327
  8. ↑ Sundberg, Jonas; Cameron, Lisa J.; Southon, Peter D.; Kepert, Cameron J.; McKenzie, Christine J. (2014). "Oxygen chemisorption/desorption in a reversible single-crystal-to-single-crystal transformation" (PDF). Chemical Science. 5 (10): 4017. doi:10.1039/C4SC01636J. ISSN 2041-6520.
  9. ↑ New material steals oxygen from air
This article is issued from Wikipedia - version of the 7/18/2016. The text is available under the Creative Commons Attribution/Share Alike but additional terms may apply for the media files.