Chemical oxygen generator
A chemical oxygen generator is a device that releases
In commercial airliners
Commercial aircraft provide
The oxidizer core is sodium chlorate (NaClO3), which is mixed with less than 5 percent barium peroxide (BaO2) and less than 1 percent potassium perchlorate (KClO4). The explosives in the percussion cap are a lead styphnate and tetrazene explosive mixture. The chemical reaction is exothermic and the exterior temperature of the canister will reach 260 °C (500 °F). It will produce oxygen for 12 to 22 minutes.[2][3] The two-mask generator is approximately 63 mm (2.5 in) in diameter and 223 mm (8.8 in) long. The three-mask generator is approximately 70 mm (2.8 in) in diameter and 250 mm (9.8 in) long.
Accidental activation of improperly shipped expired generators, mistakenly labeled as empty, caused the
Oxygen candle
A chlorate candle, or an oxygen candle, is a cylindrical chemical oxygen generator that contains a mix of
- 2 NaClO3 → 2 NaCl + 3 O2
Potassium and lithium chlorate, and sodium, potassium and lithium perchlorates can also be used in oxygen candles.
An explosion caused by one of these candles killed two Royal Navy sailors on HMS Tireless (S88), a nuclear-powered submarine, under the Arctic on 21 March 2007.[7] The candle had become contaminated with hydraulic oil, which caused the mixture to explode rather than burn.[8][failed verification]
In the Vika oxygen generator used on some spacecraft, lithium perchlorate is the source of oxygen. At 400 °C, it releases 60% of its weight as oxygen:[9]
- LiClO4 → LiCl + 2 O2
Pressure swing adsorption (PSA) oxygen generators
Advances in technology have provided industrial oxygen generator systems for use where air is available and a higher concentration of oxygen is desired.
Uses
Chemical oxygen generators are used in aircraft, breathing apparatus for firefighters and mine rescue crews, submarines, and everywhere a compact emergency oxygen generator with long shelf life is needed. They usually contain a device for absorption of carbon dioxide, sometimes a filter filled with lithium hydroxide; a kilogram of LiOH absorbs about half a kilogram of CO2.
- Self-contained oxygen generators (SCOGs) are used in submarines.
- Self-contained self-rescue devices (SCSRs) are used to facilitate escape from mines.
- On the International Space Station, chemical oxygen generators are used as a backup supply. Each canister can produce enough oxygen for one crewmember for one day.[10]
See also
- Oxygen storage
- SolidOx (welding)
References
- ^ Hayyan M., Hashim M.A., AlNashef I.M., Superoxide Ion: Generation and Chemical Implications, Chem. Rev., 2016, 116 (5), pp 3029–3085. DOI: 10.1021/acs.chemrev.5b00407
- ^ Yunchang Zhang; Girish Kshirsagar; James C. Cannon (1993). "Functions of Barium Peroxide in Sodium Chlorate Chemical Oxygen". Ind. Eng. Chem. Res. 32 (5): 966–969. .
- .
- ^ "Fire in the Hold". Mayday. Season 12. Episode 2. 10 August 2012.
- ^ Airliners.net, Photograph, Dave Campbell
- ISBN 978-0-08-037941-8.
- ^ Johnson, C. W. "Degraded Modes and the 'Culture of Coping' in Military Operations: An Analysis of a Fatal Incident on-board HMS Tireless on 20/21 March 2007" (PDF).
- ^ Page, Lewis (22 March 2007). "'Oxygen candle' caused explosion". The Register. Retrieved 2013-09-04.
- .
- National Aeronautics and Space Administration. Archived from the originalon 11 March 2019. Retrieved 9 September 2012.