Oxyhydrogen

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Nineteenth-century electrolytic cell for producing oxyhydrogen Electrolyser 1884.png
Nineteenth-century electrolytic cell for producing oxyhydrogen

Oxyhydrogen is a mixture of hydrogen (H2) and oxygen (O2) gases. This gaseous mixture is used for torches to process refractory materials and was the first [1] gaseous mixture used for welding. Theoretically, a ratio of 2:1 hydrogen:oxygen is enough to achieve maximum efficiency; in practice a ratio 4:1 or 5:1 is needed to avoid an oxidizing flame. [2]

Contents

This mixture may also be referred to as Knallgas (Scandinavian and German Knallgas ; lit. 'bang-gas'), although some authors define knallgas to be a generic term for the mixture of fuel with the precise amount of oxygen required for complete combustion, thus 2:1 oxyhydrogen would be called "hydrogen-knallgas". [3]

"Brown's gas" and HHO are terms for oxyhydrogen originating in pseudoscience, although x H2 + y O2 is preferred due to HHO meaning H2O.

Properties

Oxyhydrogen will combust when brought to its autoignition temperature. For the stoichiometric mixture in air, at normal atmospheric pressure, autoignition occurs at about 570 °C (1065 °F). [4] The minimum energy required to ignite such a mixture, at lower temperatures, with a spark is about 20 microjoules. [4] At standard temperature and pressure, oxyhydrogen can burn when it is between about 4% and 95% hydrogen by volume. [5] [4]

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. [6] The maximum temperature of about 2,800 °C (5,100 °F) is achieved with an exact stoichiometric mixture, about 700 °C (1,300 °F) hotter than a hydrogen flame in air. [7] [8] [9] 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 flame temperature will be lower. [6]

Production by electrolysis

A pure stoichiometric mixture may be 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. In theory, the input energy of a closed system always equals the output energy, as the first law of thermodynamics states. However, in practice no systems are perfectly closed, and the energy required to generate the oxyhydrogen always exceeds the energy released by combusting it, even at maximum practical efficiency, as the second law of thermodynamics implies (see Electrolysis of water#Efficiency).

Applications

Limelights used an oxyhydrogen flame as a high-temperature heat source Limelight diagram.svg
Limelights used an oxyhydrogen flame as a high-temperature heat source

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. [10] Because of the explosiveness of the oxyhydrogen, limelights have been replaced by electric lighting.

Oxyhydrogen blowpipe

Nineteenth-century bellows-operated oxy-hydrogen blowpipe, including two different types of flashback arrestor Blowpipe - circa 1827.jpg
Nineteenth-century bellows-operated oxy-hydrogen blowpipe, including two different types of flashback arrestor

The foundations of the oxy-hydrogen blowpipe were laid down by Carl Wilhelm Scheele and Joseph Priestley around the last quarter of the eighteenth century. The oxy-hydrogen blowpipe itself was developed by the Frenchman Bochard-de-Saron, the English mineralogist Edward Daniel Clarke and the American chemist Robert Hare in the late 18th and early 19th centuries. [11] It produced a flame hot enough to melt such refractory materials as platinum, porcelain, fire brick, and corundum, and was a valuable tool in several fields of science. [12] It is used in the Verneuil process to produce synthetic corundum. [13]

Oxyhydrogen torch

An oxyhydrogen torch (also known as hydrogen torch) is an oxy-gas torch that burns hydrogen (the fuel) with oxygen (the oxidizer). It is used for cutting and welding [14] metals, glasses, and thermoplastics. [10]

Due to competition from arc welding and other oxy-fuel torches such as the acetylene-fueled cutting torch, the oxyhydrogen torch is seldom used today, but it remains the preferred cutting tool in some niche applications.

Oxyhydrogen was once used in working platinum, because at the time, only it could burn hot enough to melt the metal 1,768.3 °C (3,214.9 °F). [6] These techniques have been superseded by the electric arc furnace.

Pseudoscientific claims

Oxyhydrogen is associated with various exaggerated claims. [15] [16] [17] It is often called "Brown's gas" or "HHO gas", a term popularized by fringe physicist [18] Ruggero Santilli, who claimed that his HHO gas, produced by a special apparatus, is "a new form of water", with new properties, based on his fringe theory of "magnecules". [17]

Many other pseudoscientific claims have been made about oxyhydrogen, like an ability to neutralize radioactive waste, help plants to germinate, and more. [17]

Oxyhydrogen is often mentioned in conjunction with vehicles that claim to use water as a fuel. The most common and decisive counter-argument against producing this gas on board to use as a fuel or fuel additive is that more energy is always needed to split water molecules than is recouped by burning the resulting gas. [16] [19] Additionally, the volume of gas that can be produced for on-demand consumption through electrolysis is very small in comparison to the volume consumed by an internal combustion engine. [20]

An article in Popular Mechanics in 2008 reported that oxyhydrogen does not increase the fuel economy in automobiles. [21]

"Water-fueled" cars should not be confused with hydrogen-fueled cars, where the hydrogen is produced elsewhere and used as fuel or where it is used as fuel enhancement.

Related Research Articles

<span class="mw-page-title-main">Combustion</span> Chemical reaction between a fuel and oxygen

Combustion, or burning, is a high-temperature exothermic redox chemical reaction between a fuel and an oxidant, usually atmospheric oxygen, that produces oxidized, often gaseous products, in a mixture termed as smoke. Combustion does not always result in fire, because a flame is only visible when substances undergoing combustion vaporize, but when it does, a flame is a characteristic indicator of the reaction. While activation energy must be supplied to initiate combustion, the heat from a flame may provide enough energy to make the reaction self-sustaining.

<span class="mw-page-title-main">Electrochemistry</span> Branch of chemistry

Electrochemistry is the branch of physical chemistry concerned with the relationship between electrical potential difference and identifiable chemical change. These reactions involve electrons moving via an electronically-conducting phase between electrodes separated by an ionically conducting and electronically insulating electrolyte.

<span class="mw-page-title-main">Hydrogen</span> Chemical element, symbol H and atomic number 1

Hydrogen is a chemical element; it has symbol H and atomic number 1. It is the lightest element and, at standard conditions, is a gas of diatomic molecules with the formula H2, sometimes called dihydrogen, but more commonly called hydrogen gas, molecular hydrogen or simply hydrogen. It is colorless, odorless, tasteless, non-toxic, and highly combustible. Constituting approximately 75% of all normal matter, hydrogen is the most abundant chemical substance in the universe. Stars, including the Sun, primarily consist of hydrogen in a plasma state, while on Earth, hydrogen is found in water, organic compounds, and other molecular forms. The most common isotope of hydrogen consists of one proton, one electron, and no neutrons.

<span class="mw-page-title-main">Flame</span> Visible, gaseous part of a fire

A flame is the visible, gaseous part of a fire. It is caused by a highly exothermic chemical reaction taking place in a thin zone. When flames are hot enough to have ionized gaseous components of sufficient density, they are then considered plasma.

<span class="mw-page-title-main">Industrial processes</span> Process of producing goods

Industrial processes are procedures involving chemical, physical, electrical, or mechanical steps to aid in the manufacturing of an item or items, usually carried out on a very large scale. Industrial processes are the key components of heavy industry.

<span class="mw-page-title-main">MAPP gas</span> Fuel gas based on a stabilized mixture of methylacetylene and propadiene

MAPP gas was a trademarked name, belonging to The Linde Group, a division of the former global chemical giant Union Carbide, for a fuel gas based on a stabilized mixture of methylacetylene (propyne), propadiene and propane. The name comes from the original chemical composition, methylacetylene-propadiene propane. "MAPP gas" is also widely used as a generic name for UN 1060 stabilised methylacetylene-propadiene.

<span class="mw-page-title-main">Sabatier reaction</span> Methanation process of carbon dioxide with hydrogen

The Sabatier reaction or Sabatier process produces methane and water from a reaction of hydrogen with carbon dioxide at elevated temperatures and pressures in the presence of a nickel catalyst. It was discovered by the French chemists Paul Sabatier and Jean-Baptiste Senderens in 1897. Optionally, ruthenium on alumina makes a more efficient catalyst. It is described by the following exothermic reaction:

<span class="mw-page-title-main">Water splitting</span> Chemical reaction

Water splitting is the chemical reaction in which water is broken down into oxygen and hydrogen:

Air–fuel ratio (AFR) is the mass ratio of air to a solid, liquid, or gaseous fuel present in a combustion process. The combustion may take place in a controlled manner such as in an internal combustion engine or industrial furnace, or may result in an explosion.

<span class="mw-page-title-main">Blowpipe (tool)</span> Tool used to direct a stream of gas

The term blowpipe refers to one of several tools used to direct streams of gases into any of several working media.

<span class="mw-page-title-main">Atomic hydrogen welding</span> Arc welding process under an H2 atmosphere

Atomic hydrogen welding is an arc welding process that uses an arc between two tungsten electrodes in a shielding atmosphere of hydrogen. The process was invented by Irving Langmuir in the course of his studies of atomic hydrogen. The electric arc efficiently breaks up the hydrogen molecules, which later recombine with tremendous release of heat, reaching temperatures from 3400 to 4000 °C. Without the arc, an oxyhydrogen torch can only reach 2800 °C. This is the third-hottest flame after dicyanoacetylene at 4987 °C and cyanogen at 4525 °C. An acetylene torch merely reaches 3300 °C. This device may be called an atomic hydrogen torch, nascent hydrogen torch or Langmuir torch. The process was also known as arc-atom welding.

A methane reformer is a device based on steam reforming, autothermal reforming or partial oxidation and is a type of chemical synthesis which can produce pure hydrogen gas from methane using a catalyst. There are multiple types of reformers in development but the most common in industry are autothermal reforming (ATR) and steam methane reforming (SMR). Most methods work by exposing methane to a catalyst at high temperature and pressure.

Oxygenevolution is the process of generating molecular oxygen (O2) by a chemical reaction, usually from water. Oxygen evolution from water is effected by oxygenic photosynthesis, electrolysis of water, and thermal decomposition of various oxides. The biological process supports aerobic life. When relatively pure oxygen is required industrially, it is isolated by distilling liquefied air.

<span class="mw-page-title-main">Oxy-fuel welding and cutting</span> Metalworking technique using a fuel and oxygen

Oxy-fuel welding and oxy-fuel cutting are processes that use fuel gases and oxygen to weld or cut metals. French engineers Edmond Fouché and Charles Picard became the first to develop oxygen-acetylene welding in 1903. Pure oxygen, instead of air, is used to increase the flame temperature to allow localized melting of the workpiece material in a room environment. A common propane/air flame burns at about 2,250 K, a propane/oxygen flame burns at about 2,526 K, an oxyhydrogen flame burns at 3,073 K and an acetylene/oxygen flame burns at about 3,773 K.

<span class="mw-page-title-main">Solid oxide electrolyzer cell</span> Type of fuel cell

A solid oxide electrolyzer cell (SOEC) is a solid oxide fuel cell that runs in regenerative mode to achieve the electrolysis of water by using a solid oxide, or ceramic, electrolyte to produce hydrogen gas and oxygen. The production of pure hydrogen is compelling because it is a clean fuel that can be stored, making it a potential alternative to batteries, methane, and other energy sources. Electrolysis is currently the most promising method of hydrogen production from water due to high efficiency of conversion and relatively low required energy input when compared to thermochemical and photocatalytic methods.

<span class="mw-page-title-main">Hydrogen internal combustion engine vehicle</span> Vehicle with hydrogen internal combustion engine

A hydrogen internal combustion engine vehicle (HICEV) is a type of hydrogen vehicle using an internal combustion engine. Hydrogen internal combustion engine vehicles are different from hydrogen fuel cell vehicles. Instead, the hydrogen internal combustion engine is simply a modified version of the traditional gasoline-powered internal combustion engine. The absence of carbon means that no CO2 is produced, which eliminates the main greenhouse gas emission of a conventional petroleum engine.

<span class="mw-page-title-main">Oxidizing and reducing flames</span>

A flame is affected by the fuel introduced and the oxygen available. A flame with a balanced oxygen-fuel ratio is called a neutral flame. The color of a neutral flame is semi-transparent purple or blue. This flame is optimal for many uses because it does not oxidize or deposit soot onto surfaces.

Thermochemical cycles combine solely heat sources (thermo) with chemical reactions to split water into its hydrogen and oxygen components. The term cycle is used because aside of water, hydrogen and oxygen, the chemical compounds used in these processes are continuously recycled.

<span class="mw-page-title-main">Rocket propellant</span> Chemical or mixture used as fuel for a rocket engine

Rocket propellant is the reaction mass of a rocket. This reaction mass is ejected at the highest achievable velocity from a rocket engine to produce thrust. The energy required can either come from the propellants themselves, as with a chemical rocket, or from an external source, as with ion engines.

Chemical looping reforming (CLR) and gasification (CLG) are the operations that involve the use of gaseous carbonaceous feedstock and solid carbonaceous feedstock, respectively, in their conversion to syngas in the chemical looping scheme. The typical gaseous carbonaceous feedstocks used are natural gas and reducing tail gas, while the typical solid carbonaceous feedstocks used are coal and biomass. The feedstocks are partially oxidized to generate syngas using metal oxide oxygen carriers as the oxidant. The reduced metal oxide is then oxidized in the regeneration step using air. The syngas is an important intermediate for generation of such diverse products as electricity, chemicals, hydrogen, and liquid fuels.

References

  1. ↑ Howard Monroe Raymond (1916), "Oxy-Hydrogen Welding", Modern Shop Practice volume 1, American Technical Society, archived from the original on March 6, 2011
  2. ↑ Viall, Ethan (1921). Gas Torch and Thermite Welding. McGraw-Hill. p.  10. Archived from the original on August 3, 2016.
  3. ↑ W. Dittmar, "Exercises in quantitative chemical analysis", 1887, p. 189 Archived June 27, 2014, at the Wayback Machine
  4. 1 2 3 O'Connor, Ken. "Hydrogen" (PDF). NASA Glenn Research Center Glenn Safety Manual. Archived from the original (PDF) on February 2, 2013.
  5. ↑ Moyle, Morton; Morrison, Richard; Churchill, Stuart (March 1960). "Detonation Characteristics of Hydrogen Oxygen Mixtures" (PDF). AIChE Journal. 6 (1): 92–96. Bibcode:1960AIChE...6...92M. doi:10.1002/aic.690060118. hdl: 2027.42/37308 .
  6. 1 2 3 Chisholm, Hugh, ed. (1911). "Oxyhydrogen Flame"  . Encyclopædia Britannica . Vol. 20 (11th ed.). Cambridge University Press. p. 424.
  7. ↑ Calvert, James B. (April 21, 2008). "Hydrogen". University of Denver. Archived from the original on April 18, 2009. Retrieved April 23, 2009. An air-hydrogen torch flame reaches 2045 °C, while an oxyhydrogen flame reaches 2660 °C.
  8. ↑ "Adiabatic Flame Temperature". The Engineering Toolbox. Archived from the original on January 28, 2008. Retrieved April 23, 2009. "Oxygen as Oxidizer: 3473 K, Air as Oxidizer: 2483 K"
  9. ↑ "Temperature of a Blue Flame". Archived from the original on March 16, 2008. Retrieved April 5, 2008. "Hydrogen in air: 2,400 K, Hydrogen in Oxygen: 3,080 K"
  10. 1 2 Tilden, William Augustus (1926). Chemical Discovery and Invention in the Twentieth Century. Adamant Media Corporation. p. 80. ISBN   978-0-543-91646-4.
  11. ↑ Hofmann, A. W. (1875). "Report on the Development of the Chemical Arts During the Last Ten Years". Chemical News. Manufacturing chemists.
  12. ↑ Griffin, John Joseph (1827). A Practical Treatise on the Use of the Blowpipe in Chemical and Mineral Analysis. Glasgow: R. Griffin & co.
  13. ↑ "Verneuil process". Encyclopaedia Britannica. October 22, 2013. Retrieved July 11, 2018.
  14. ↑ P. N. Rao (2001), "24.4 Oxyhydrogen welding", Manufacturing technology: foundry, forming and welding (2 ed.), Tata McGraw-Hill Education, pp. 373–374, ISBN   978-0-07-463180-5, archived from the original on June 27, 2014
  15. ↑ "Eagle Research Institute - Brown's Gas - Myth-conceptions". Archived from the original on April 18, 2019. Retrieved July 11, 2018.
  16. 1 2 Ball, Philip (September 10, 2007). "Burning water and other myths". News@nature. Springer Nature. doi: 10.1038/news070910-13 . ISSN   1744-7933. S2CID   129704116.
  17. 1 2 3 Ball, Philip (2006). "Nuclear waste gets star attention". News@nature. doi:10.1038/news060731-13. ISSN   1744-7933. S2CID   121246705.
  18. ↑ Weimar, Carrie (May 7, 2007). "Snubbed By Mainstream, Scientist Sues". St. Petersburg Times. Retrieved February 3, 2011.
  19. ↑ Schadewald, R.J. (2008). Worlds of Their Own: A Brief History of Misguided Ideas: Creationism, Flat-Earthism, Energy Scams, and the Velikovsky Affair. Xlibris US. ISBN   978-1-4628-1003-1 . Retrieved July 11, 2018.
  20. ↑ Simpson, Bruce (May 2008). "The proof that HHO is a scam". Aardvark Daily. Archived from the original on February 11, 2012. Retrieved February 12, 2012.
  21. ↑ Water-Powered Cars: Hydrogen Electrolyzer Mod Can't Up MPGs Archived March 20, 2015, at the Wayback Machine , Mike Allen, August 7, 2008, Popularmechanics.com
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