Oxyhydrogen
Oxyhydrogen is a mixture of hydrogen (H2) and oxygen (O2) gases, typically in a 2:1 molar ratio, the same proportion as water.[1] This gaseous mixture is used for torches for the processing of refractory materials.[citation needed]
Properties
At normal temperature and pressure, oxyhydrogen can burn when it is between about 4% and 95% hydrogen by volume.[2] When ignited, the gas mixture converts to water vapor and releases energy, which sustains the reaction: 241.8 kJ of energy (LHV) for every mole of Template:Hydrogen burned. The amount of heat energy released is independent of the mode of combustion, but the temperature of the flame varies.[1] The maximum temperature of about 2800 °C is achieved with a pure stoichiometric mixture, about 700 degrees hotter than a hydrogen flame in air.[3][4][5] When either of the gases are mixed in excess of this ratio, or when mixed with an inert gas like nitrogen, the heat must spread throughout a greater quantity of matter and the temperature will be lower.[1]
Applications
Lighting
Many forms of oxyhydrogen lamps have been described, such as the limelight, which used an oxyhydrogen flame to heat a piece of lime to white hot incandescence.[6] Because of the explosiveness of the oxyhydrogen, limelights have been replaced by electric lighting.
Oxyhydrogen was once used in working platinum because at the time such a torch was the only device that could attain the temperature required to melt the metal (1768.3 °C).[1] These techniques have been superseded by the electric arc furnace.
Oxyhydrogen torch
An oxyhydrogen torch is an oxy-gas torch, which burns hydrogen (the fuel) with oxygen (the oxidizer). It is used for cutting and welding metals, glass, and thermoplastics.[6] An oxyhydrogen torch is used in the glass industry for "fire polishing"; slightly melting the surface of glass to remove scratches and dullness.[citation needed]
The oxyhydrogen torch is seldom used in metal work because of its lack of high specific heat.
The oxyhydrogen flame begins a short distance from the torch tip; if the distance is great enough the torch tip can remain relatively cool.[7]
Automotive
Oxyhydrogen is often mentioned in conjunction with devices that claim to operate a car using water as a fuel. Because the energy required to split water exceeds the energy recouped by burning it, these devices reduce, rather than improve fuel efficiency.[9][10]
Production
A pure stoichiometric mixture is most easily obtained by water electrolysis, which uses an electric current to dissociate the water molecules:
- electrolysis: 2 H2O → 2 H2 + O2
- combustion: 2 H2 + O2 → 2 H2O
William Nicholson was the first to decompose water in this manner in 1800. The energy required to generate the oxyhydrogen always exceeds the energy released by combusting it. (See Electrolysis of water#Efficiency).
Water torch
A water torch is a kind of oxyhydrogen torch, that is fed by oxygen and hydrogen generated on demand by water electrolysis. The device avoids the need for bottled oxygen and hydrogen, but requires electricity and distilled water. Some models of water torches mix the two gases immediately after production rather than at the torch tip, allegedly making the gas mixture more accurate.[11] This electrolyzer design is referred to as "common-ducted,"[7] and the first was invented by William A. Rhodes in 1966.[12] Water torches must be designed to mitigate flashback by strengthening the electrolytic chamber. Use of an intermediary water bubbler eliminates potential electrolyzer damage from flashback, but the flame speed is too high for the dry flashback arrestor to be effective. The bubbler is connected directly in series with the output gas. A water bubbler is sometimes referred to as a wet flashback arrestor, and effectively captures any remaining electrolyte in the output gas. Suitable electrolytes include sodium or potassium hydroxide, and other salts that ionize well.[7] Also, "the electrolyzer system must be of high enough pressure to keep the gas velocity at the nozzle above the combustion velocity of the flame, or the system will backfire."[7]
Yull Brown's design
Oxyhydrogen gas produced in a common-ducted electrolyzer has been referred to as "Brown's gas"[13] after Yull Brown, a Bulgarian inventor naturalised in Australia.[14] Brown received two patents for a series cell common-ducted electrolyzer in 1977 and 1978.[11][15] Brown's torches also used an electric arc to increase the temperature of the flame.[11]
Dennis Klein and Aquygen
The firm Hydrogen Technology Applications (HTA) has trademarked the term "Aquygen" to refer to oxyhydrogen.[16][17][18] HTA's founder Dennis Klein holds a patent for an electrolyzer design which states that it differs from Yull Brown's patents.[19] The claimed applications of "Aquygen" are practically indistinguishable from the original claims of Yull Brown, in that both can be used for welding and allegedly improving fuel efficiency in cars.
References
- ^ a b c d 1911 Encyclopedia. "Oxyhydrogen Flame." (Available here Accessed 2008-01-19.)
- ^ O'Connor, Ken. "Hydrogen". NASA Glenn Research Center Glenn Safety Manual.
{{cite book}}: External link in|chapterurl=|chapterurl=ignored (|chapter-url=suggested) (help) - ^ Calvert, Dr. James B. (2006-09-09). "Hydrogen". University of Denver faculty page. Retrieved 2008-04-05. "An air-hydrogen torch flame reaches 2045 °C, while an oxyhydrogen flame reaches 2660 °C."
- ^ "Adiabatic Flame Temperature". The Engineering Toolbox. Retrieved 2008-04-05. "Oxygen as Oxidizer: 3079 K, Air as Oxidizer: 2384 K"
- ^ "Temperature of a Blue Flame". Retrieved 2008-04-05. "Hydrogen in air: 2,400 K, Hydrogen in Oxygen: 3,080 K"
- ^ a b William Augustus Tilden. Chemical Discovery and Invention in the Twentieth Century. Adamant Media Corporation. p. 80. ISBN 0543916464.
- ^ a b c d George Wiseman. Brown's Gas Book 2. Eagle Research. p. 59. ISBN 1895882192.
- ^ US 4936961 Method for the production of a fuel gas - Stanley A. Meyer
- ^ Schadewald, Robert J. (2008), Worlds of Their Own - A Brief History of Misguided Ideas: Creationism, Flat-Earthism, Energy Scams, and the Velikovsky Affair, Xlibris, ISBN 978-1-4636-0435-1
{{citation}}: Check|isbn=value: checksum (help) - ^ Barton, Peter (2004), ERMD Report # 2004-032 Study of Heavy Duty Vehicle Exhaust Emissions and Fuel Consumption with the use of a JetStar™ Hydrogen Gas Generator (PDF), Environmental Technology Centre, Environment Canada
- ^ a b c d e US patent 4014777, Yull Brown, "Welding", issued 1977-03-29
- ^ US patent 3262872, William Rhodes, "Generator Patent", issued 1966-07-26
- ^ newsreview: Hydrogen generators get a test drive in the search for fuel economy and lower emissions By Scott D.F. Reeves
- ^ Spolet online: Tanto per citarne una sull'alternativo
- ^ US patent 4081656, Yull Brown, "Arc-assisted oxy/hydrogen welding", issued 1978-03-28
- ^ Business Wire Hydrogen Technology Applications and UTEK Corporation Announce Strategic Alliance Agreement (April, 2002)
- ^ EVWORLD FEATURE: Electric Cars and the Goldilocks Planet: Global Warming | Carbon Dioxide | Cold Fusion
- ^ Knight-Ridder/Tribune Business News: Clearwater man puts technology to work Tampa Tribune (Tampa, Florida) (November, 2005)]
- ^ US patent 6,689,259, Dennis Klein, "Mixed gas generator", issued 2004-2-10
This article incorporates text from a publication now in the public domain: Chisholm, Hugh, ed. (1911). Encyclopædia Britannica (11th ed.). Cambridge University Press. {{cite encyclopedia}}: Missing or empty |title= (help)
