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词条 Autoignition temperature
释义

  1. Autoignition equation

  2. Autoignition point of selected substances

  3. See also

  4. References

  5. External links

The autoignition temperature or kindling point of a substance is the lowest temperature at which it spontaneously ignites in normal atmosphere without an external source of ignition, such as a flame or spark. This temperature is required to supply the activation energy needed for combustion. The temperature at which a chemical ignites decreases as the pressure or oxygen concentration increases. It is usually applied to a combustible fuel mixture.

Autoignition temperatures of liquid chemicals are typically measured using a {{convert|500|ml|adj=on}} flask placed in a temperature-controlled oven in accordance with the procedure described in ASTM E659.[1]

When measured for plastics, autoignition temperature can be also measured under elevated pressure and at 100% oxygen concentration. The resulting value is used as a predictor of viability for high-oxygen service. The main testing standard for this is ASTM G72.[2]

Autoignition equation

The time it takes for a material to reach its autoignition temperature when exposed to a heat flux is given by the following equation:[3]

where k = thermal conductivity, ρ = density, and c = specific heat capacity of the material of interest, is the initial temperature of the material (or the temperature of the bulk material).

Autoignition point of selected substances

Temperatures vary widely in the literature and should only be used as estimates. Factors that may cause variation include partial pressure of oxygen, altitude, humidity, and amount of time required for ignition. Generally the autoignition temperature for hydrocarbon/air mixtures decreases with increasing molecular mass and increasing chain length. The autoignition temperature is also higher for branched-chain hydrocarbons than for straight-chain hydrocarbons.[4]

Substance Autoignition{{ref label|standCond|D|DNote
Barium 550|C|F|sortable=on|abbr=on}}[5]{{ref label>Pressure|C|C}}
Bismuth 735|C|F|sortable=on|abbr=on}}[5]{{ref label>Pressure|C|C}}
Butane 405|C|F|sortable=on|abbr=on}} [6]
Calcium 790|C|F|sortable=on|abbr=on}}[5]{{ref label>Pressure|C|C}}
Carbon disulfide 90|C|F|sortable=on|abbr=on}} [9]
Diesel or Jet A-1 210|C|F|sortable=on|abbr=on}} [10]
Diethyl ether 160|C|F|sortable=on|abbr=on}} [7]
Ethanol 365|C|F|sortable=on|abbr=on}} [8]
Gasoline (Petrol) 247|-|280|C|F|sortable=on|abbr=on}} [8]
Hydrogen 536|C|F|sortable=on|abbr=on}} [9]
Iron 1315|C|F|sortable=on|abbr=on}}[5]{{ref label>Pressure|C|C}}
Lead 850|C|F|sortable=on|abbr=on}}[5]{{ref label>Pressure|C|C}}
Leather / parchment 200|-|212|C|F|sortable=on|abbr=on}} [10][11]
Magnesium 635|C|F|sortable=on|abbr=on}}[5]{{ref label>Magnesium|B|B}}{{ref label|Pressure|C|C}}
Magnesium 473|C|F|sortable=on|abbr=on}}[8]{{ref label>Magnesium|B|B}}
Molybdenum 780|C|F|sortable=on|abbr=on}}[5]{{ref label>Pressure|C|C}}
Paper 218|-|246|C|F|sortable=on|abbr=on}} [10][12]
Phosphorus,white34|C|F|sortable=on|abbr=on}}[8]{{ref label>Phosphorus|A|A}}{{ref label|Magnesium|B|B}}
Silane 21|C|F|sortable=on|abbr=on}} [8] or below
Strontium 1075|C|F|sortable=on|abbr=on}}[5]{{ref label>Pressure|C|C}}
Tin 940|C|F|sortable=on|abbr=on}}[5]{{ref label>Pressure|C|C}}
Triethylborane -20|C|F|sortable=on|abbr=on}} [8]
Phosphorus|A|A}} On contact with an organic substance, melts otherwise.
Magnesium|B|B}} There are two distinct results in the published literature. Both are separately listed in this table.
Pressure|C|C}} At 1 atm. The ignition temperature depends on the air pressure.
standCond|D|D}}Under standard conditions for pressure.

See also

  • Pyrolysis
  • Fire point
  • Flash point
  • Gas burner (For flame temperatures, combustion heat energy values and ignition temperatures)
  • Spontaneous combustion

References

1. ^E659 – 78 (Reapproved 2000), "Standard Test Method for Autoignition Temperature of Liquid Chemicals", ASTM, 100 Barr Harbor Drive, West Conshohocken, PA 19428-2959.
2. ^S. Grynko, "Material Properties Explained" (2012), {{ISBN|1-4700-7991-7}}, p. 46.
3. ^Principles of Fire Behavior. {{ISBN|0-8273-7732-0}}. 1998.
4. ^Zabetakis, M. G. (1965), Flammability characteristics of combustible gases and vapours, U.S. Department of Mines, Bulletin 627.
5. ^1 2 3 4 5 6 7 8 {{cite journal |last1=Laurendeau |first1=N. M. |last2=Glassman |first2=I. |title=Ignition Temperatures of Metals in Oxygen Atmospheres |journal=Combustion Science and Technology |date=1971-04-01|volume=3 |issue=2 |pages=77–82 |doi=10.1080/00102207108952274 |language=English}}
6. ^{{cite web |url=http://www.wolframalpha.com/input/?i=butane|title=Butane - Safety Properties |publisher=Wolfram|Alpha}}
7. ^{{cite web |url=http://www.wolframalpha.com/input/?i=diethyl+ether|title=Diethyl Ether - Safety Properties |publisher=Wolfram|Alpha}}
8. ^1 2 3 4 5 6 {{citation |url=http://www.engineeringtoolbox.com/fuels-ignition-temperatures-d_171.html |title=Fuels and Chemicals - Autoignition Temperatures |publisher=engineeringtoolbox.com}}
9. ^{{cite web |url=http://www.wolframalpha.com/input/?i=hydrogen&a=*C.hydrogen-_*Chemical-|title=Hydrogen - Safety Properties |publisher=Wolfram|Alpha}}
10. ^1 2 {{cite web|last1=Cafe|first1=Tony|title=PHYSICAL CONSTANTS FOR INVESTIGATORS|url=http://www.tcforensic.com.au/docs/article10.html|website=tcforensic.com.au|publisher=TC Forensic P/L.|accessdate=11 February 2015}}
11. ^{{cite web|title=Flammability and flame retardancy of leather|url=http://www.leathermag.com/features/featureflammability-and-flame-retardancy-of-leather/|website=leathermag.com|publisher=Leather International / Global Trade Media|accessdate=11 February 2015}}
12. ^{{cite journal |url=http://www.tcforensic.com.au/docs/article10.html |title=Physical Constants for Investigators|author=Tony Cafe |journal=Journal of Australian Fire Investigators}} (Reproduced from "Firepoint" magazine)
{{refbegin}}{{refend}}

External links

  • Analysis of Effective Thermal Properties of Thermally Thick Materials.
{{Firelighting}}{{DEFAULTSORT:Autoignition Temperature}}Självantändning#Självantändningspunkt

3 : Chemical properties|Fire|Threshold temperatures
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