Oxyhydrogen

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"Knallgas" redirects here. For bacteria which oxidize hydrogen, see Knallgas-bacteria.

Contents

Oxyhydrogen is a mixture of hydrogen and oxygen gases, typically in a 2:1 atomic ratio, the same proportion as water.[1] This gaseous mixture is widely used for torches for the processing of refractory materials.[citation needed]

[edit] Properties

Oxyhydrogen will combust when brought to its autoignition temperature. For a stoichiometric mixture at normal atmospheric pressure, autoignition occurs at about 570 °C (1065 °F).[2] The minimum energy required to ignite such a mixture with a spark is about 20 microjoules.[2] At normal temperature and pressure, oxyhydrogen can burn when it is between about 4% and 94% 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 H2 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 is 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]

[edit] Applications - Historical

Limelights used an oxyhydrogen flame as a high-temperature heat source
Limelights used an oxyhydrogen flame as a high-temperature heat source

[edit] 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to heat a piece of lime to white hot incandescence.[6] Because of the explosiveness of the oxyhydrogen, limelights have been replaced by electric lighting.

It was much used in platinum works,[citation needed] as platinum could be melted (at a temperature of 1768.3 °C) only in an oxyhydrogen flame, or an electric furnace (which is now used instead).

[edit] Oxyhydrogen torch

A flame created by the combustion of the constituent gases in an oxyhydrogen mixture. The only product is water
A flame created by the combustion of the constituent gases in an oxyhydrogen mixture. The only product is water

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 flame begins a short distance from the torch tip; if the distance is great enough the torch tip can remain relatively cool.[7]

[edit] Applications - Claimed

[edit] Automotive

Oxyhydrogen is often mentioned in conjunction with devices that claim to increase automotive engine efficiency. See water-fuelled car

Many of these claims,prima facie, violate the Law of conservation of energy. See Conservation of energy and Electrolysis of water:Efficiency. To date, all of these claims have been fraudulent.

[edit] 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

The energy required to generate the oxyhydrogen always exceeds the energy released by combusting it. (See Electrolysis of water:Efficiency).

[edit] Water torch

A bubbler apparatus used to mitigate potential flashback.
A bubbler apparatus used to mitigate potential flashback.[8]

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, and requires electricity. Some models of water torches mix the two gases immediately after production (vs. the torch tip) making the gas mixture more accurate.[8] This electrolyzer design is referred to as "common-ducted",[7] and the first was invented by William A. Rhodes in 1966.[9] 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, with a dry flashback arrestor being ineffective due to flame velocity. 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] For images of water torch equipment see these links: [1] [2] [3][4][5][6][7][8].

The series cell design by Yull Brown.
The series cell design by Yull Brown.[8]

[edit] Brown's design

Oxyhydrogen gas produced in a common-ducted electrolyzer has been referred to as "Brown's gas",[citation needed] after Yull Brown who received a utility patent for a series cell common-ducted electrolyzer in 1977 and 1978 (the term "Brown's gas" is not used in his patents, but "a mixture of oxygen and hydrogen" is referenced).[8][10] Brown's torches also used an electric arc to increase the temperature of the flame (called atomic welding):[8]



[edit] Aquygen

The firm Hydrogen Technology Applications (HTA) has trademarked oxyhydrogen as Aquygen. HTA's founder Dennis Klein holds a patent for an electrolyzer design which states that it differs from Yull Brown's torch patents in that it lacks an electric arc feature.[11]

The claimed applications of HHO and Aquygen are practically indistinguishable from the original claims of Yull Brown. The HHO trademark is associated with an unproven state of matter called magnegases, and a discredited theory about magnecules,[12] which is the basis for a number of fraudulent claims, and third party water-fuelled car scam attempts.

[edit] References

  1. ^ a b c 1911 Encyclopedia. "Oxyhydrogen Flame". (Available here Accessed 2008-01-19.)
  2. ^ a b c O'Connor, Ken. "Hydrogen", NASA Glenn Research Center Glenn Safety Manual. 
  3. ^ Calvert, Dr. James B. (2006-09-09). Hydrogen. University of Denver faculty page. Retrieved on 2008-04-05. "An air-hydrogen torch flame reaches 2045 °C, while an oxyhydrogen flame reaches 2660 °C."
  4. ^ Adiabatic Flame Temperature. The Engineering Toolbox. Retrieved on 2008-04-05. "Oxygen as Oxidizer: 3079 K, Air as Oxidizer: 2384 K"
  5. ^ Temperature of a Blue Flame. Retrieved on 2008-04-05. "Hydrogen in air: 2,400 K, Hydrogen in Oxygen: 3,080 K"
  6. ^ a b William Augustus Tilden. Chemical Discovery and Invention in the Twentieth Century. Adamant Media Corporation, 80. ISBN 0543916464. 
  7. ^ a b c d George Wiseman. Brown's Gas Book 2. Eagle Research, 59. ISBN 1895882192. 
  8. ^ a b c d e US4,014,777 (PDF version) (1977-03-29) Yull Brown Welding 
  9. ^ US3,262,872 (PDF version) (1966-7-26) William Rhodes Generator Patent 
  10. ^ US4,081,656 (PDF version) (1978-3-28) Yull Brown Arc-assisted oxy/hydrogen welding 
  11. ^ US6,689,259 (PDF version) (2004-2-10) Dennis Klein Mixed gas generator 
  12. ^ J. M. Calo (November 3, 2006). "Comments on “A new gaseous and combustible form of water,” by R.M. Santilli (Int. J. Hydrogen Energy 2006: 31(9), 1113–1128)". International Journal of Hydrogen Energy (32): p. 1309–1312. doi:10.1016/j.ijhydene.2006.11.004

This article incorporates text from the Encyclopædia Britannica Eleventh Edition, a publication now in the public domain.

[edit] External links