spontaneous combustion


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spontaneous combustion,

phenomenon in which a substance unexpectedly bursts into flame without apparent cause. In ordinary combustioncombustion,
rapid chemical reaction of two or more substances with a characteristic liberation of heat and light; it is commonly called burning. The burning of a fuel (e.g., wood, coal, oil, or natural gas) in air is a familiar example of combustion.
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, a substance is deliberately heated to its ignition point to make it burn. Many substances undergo a slow oxidation that, like the rapid oxidation of burning, releases heat. If the heat so released cannot escape the substance, the temperature of the substance rises until ignition takes place. Spontaneous combustion often occurs in piles of oily rags, green hay, leaves, or coal; it can constitute a serious fire hazard.
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Spontaneous combustion

The instantaneous bursting into flames of a substance due to a chemical reaction of its own constituents, such as oily rags in an unventilated pile of rubbish.
Illustrated Dictionary of Architecture Copyright © 2012, 2002, 1998 by The McGraw-Hill Companies, Inc. All rights reserved
The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.

Spontaneous Combustion

 

a rapid increase in the rate of chemical reactions leading under certain external conditions to the combustion of fuel-oxidizer mixtures in the absence of a flame or glowing object.

Spontaneous combustion can manifest itself either as a thermal or a chain process. The basic principles of thermal spontaneous combustion were explained in qualitative form by J. Van’t Hoff in 1883, and the theory was worked out more fully by N. N. Semenov in 1928. Heat liberated during slow exothermic reactions is normally dissipated in the surroundings. However, under certain conditions of temperature, pressure, and heat removal, this heat cannot be transferred to the surroundings, and the temperature in the reaction zone steadily rises. The reaction rate and the rate of heat production increase with the temperature; the rate of heat transfer also increases but more slowly than that of the reaction. The temperature at which the heat produced begins to exceed the heat dissipated is called the spontaneous combustion temperature. This temperature clearly depends both on the chemical composition of the fuel-oxidizer mixture and on the provisions for thermal transfer. Beginning at the spontaneous combustion temperature, heat is steadily added to the mixture and the reaction rate is steadily increased; the result is either thermal spontaneous combustion or an explosion. The theory of thermal spontaneous combustion permits a calculation of the temperature of spontaneous combustion if the thermal properties of the gaseous fuel-oxidizer mixture (heat of combustion, thermal conductivity) and kinetics of the combustion reaction (rate constant, activation energy) are known.

The theory of spontaneous combustion through chain processes was also worked out by Semenov (1928). Under certain external conditions, the rates of chain branching exceed the rates of the chain-terminating steps. As a result, a slow reaction may become autocatalytic. In these cases, the temperature of the mixture is almost immaterial; the reaction becomes autocatalytic and proceeds because of chain branching, even when the temperature of the mixture is held constant.

The most common form of spontaneous combustion is one involving a combination of chain and thermal process. Quantitative calculations based on the theories of thermal and chain spontaneous combustion have great practical importance in manufacturing processes involving oxidation, in particular, combustion.

REFERENCES

Semenov, N. N. Tsepnye reaktsii. [Leningrad] 1934.
Semenov, N. N. “Teplovaia teoriia goreniia i vzryvov.” Uspekhi fizicheskikh nauk, 1940, vol. 23, issue 3.
The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.

spontaneous combustion

[spän′tā·nē·əs kəm′bəs·chən]
(chemistry)
Ignition that can occur when certain materials such as tung oil are stored in bulk, resulting from the generation of heat, which cannot be readily dissipated; often heat is generated by microbial action. Also known as spontaneous ignition.
(mechanical engineering)
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.

spontaneous combustion

the ignition of a substance or body as a result of internal oxidation processes, without the application of an external source of heat, occurring in finely powdered ores, coal, straw, etc.
Collins Discovery Encyclopedia, 1st edition © HarperCollins Publishers 2005
References in periodicals archive ?
Spontaneous combustion of coal has been reported in different coalfields of the world (USA: Heffern et al., 1983,1993; foit et al., 1987;Cosca et al., 1989; Heffern & Coates, 1997, Lyman & Volkmer, 2001; India: Prakash et al., 1997; Romania: Radan & Radan, 1998; Australia: Ellyett & Fleming, 1974, New Zealand: Lindqvist et al., 1985, China: Zhang, 1998; de Boer et al., 2001).
"Spontaneous combustion is a fairly rare occurrence," he adds, though materials like metal filings and some lab chemicals, such as sodium or phosphorous, can also self-ignite.
A few days later, spontaneous combustion touched off a fire inside the sarcophagus.
As things are, I sometimes think a third party will be sparked by the spontaneous combustion of sheer desperation.
The manufacturers insisted the inferno could have been started by an iron, light fitting or "spontaneous combustion".
As they rot down, they heat up, and the greater the number of bales, the bigger the chance of spontaneous combustion.
Mr Latack, who travelled from Michigan, USA, to attend the inquest, said he believed the fire had been caused by the spontaneous combustion of towels in the dryer.
JUNCTION CITY - The Oregon Fire Marshal has ruled that the fire that burned a $1.5 million hay harvest early Friday evening was caused by spontaneous combustion, Junction City Fire Capt.
Spontaneous combustion of coal in goaf is one of the main natural disasters in coal mine production [1, 2].
According to Ford, a buildup of acetone in the body (which can result from alcoholism, diabetes or a specific kind of diet) can lead to spontaneous combustion," it added.

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