Jet Fuel

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How much jet fuel was in the Twin Towers?

Other Hydrocarbons

Structural Steel

World Trade Center Fire Smoke Color


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(image from manchester.edu)


Considering, in a simplistic form, different fuel types and ventilation conditions, BSEN1991-1-2 : 2002 and PD7974-1 : 2003 provides the following nominal temperature-time curves:


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(manchester.edu)


PD7974-1 standard: A large pool hydrocarbon fire can reach the limit of:

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which is 1120C = 2048F


Jet Fuel open air burning temperature 260-315°C (500-599°F)

Jet Fuel maximum burning temperature 980°C (1796 °F)

Source: http://mepetroleum.com/jet_fuel.htm


It is believed that almost all of the jet fuel that remained on the impact floors was consumed in the first few minutes of the fire. fema.gov_p22

Commercial jet fuel is refined kerosene. Airliners use "Jet A" kerosene , also know as fuel oil #1, range oil, coal oil and aviation fuel. Jet fuel is a colorless, combustible petroleum distillate liquid. It weighs about 3.1 kg/gal (0.81kg/L). It is comprised of hydrocarbons with a carbon range of C9 - C17. The hydrocarbons are mainly alkanes <html>C<sub>n</sub>H<sub>2n+2</sub></html>, with n ranging from 9 to 17. It has a flash point within the range 42&deg; C - 72&deg; C (110&deg; F - 162&deg; F). And an autoignition temperature of 210&deg; C (410&deg; F). Kerosene has an [Jet Fuel Energy vs Density energy density] of 43.28MJ/kg, 18,810Btu/lb, 35.08MJ/L, or 125,800But/gal.

Depending on the supply of oxygen, jet fuel burns by one of three chemical reactions:

<html> <html><br>

(1) <font color=red>C<sub>n</sub>H<sub>2n+2</sub> + (3n+1)/2 O<sub>2</sub> => n CO<sub>2</sub> + (n + 1) H<sub>2</sub>O</font> </html>( jet burner ) or ( pre-mixed flame )<html>

<br><br>

(2) <font color=red>C<sub>n</sub>H<sub>2n+2</sub> + (2n+1)/2 O<sub>2</sub> => n CO + (n + 1) H<sub>2</sub>O</font> </html>( diffuse flame )<html>

<br><br>

(3) <font color=red>C<sub>n</sub>H<sub>2n+2</sub> + (n+1)/2 O<sub>2</sub> => n C + (n + 1) H<sub>2</sub>O</font> </html>( diffuse flame ) </html>

Reaction (1) occurs when jet fuel is well mixed with air before being burnt, as for example, in jet engines.

Reactions (2) and (3) occur when a pool of jet fuel burns. When reaction (3) occurs the carbon formed shows up as soot in the flame. This makes the smoke very dark.


If the fuel and the oxidant start at ambient temperature, a maximum flame temperature can be defined. For carbon burning in pure oxygen, the maximum is 3,200°C; for hydrogen it is 2,750°C. Thus, for virtually any hydrocarbons, the maximum flame temperature, starting at ambient temperature and using pure oxygen, is approximately 3,000°C.


This maximum flame temperature is reduced by two-thirds if air is used rather than pure oxygen. The reason is that every molecule of oxygen releases the heat of formation of a molecule of carbon monoxide and a molecule of water. If pure oxygen is used, this heat only needs to heat two molecules (carbon monoxide and water), while with air, these two molecules must be heated plus four molecules of nitrogen. Thus, burning hydrocarbons in air produces only one-third the temperature increase as burning in pure oxygen because three times as many molecules must be heated when air is used. The maximum flame temperature increase for burning hydrocarbons (jet fuel) in air is, thus, about 1,000°C - hardly sufficient to melt steel at 1,500°C.


But it is very difficult to reach this maximum temperature with a diffuse flame. There is nothing to ensure that the fuel and air in a diffuse flame are mixed in the best ratio. Typically, diffuse flames are fuel rich, meaning that the excess fuel molecules, which are unburned, must also be heated. It is known that most diffuse fires are fuel rich because blowing on a campfire or using a blacksmith’s bellows increases the rate of combustion by adding more oxygen. This fuel-rich diffuse flame can drop the temperature by up to a factor of two again. This is why the temperatures in a residential fire are usually in the 500°C to 650°C range. It is known that the WTC fire was a fuel-rich, diffuse flame as evidenced by the copious black smoke. Soot is generated by incompletely burned fuel; hence, the WTC fire was fuel rich. tms.org


chp6_engine6_1.jpg


The highest temperature inside a jet engine is located in the inner core of the stoichiometric flame in the combustion section which can reach 2050ºC (3725ºF). chevron.com

The maximum burning temperature of JETA outside a jet engine is 980 °C (1796 °F). (aka a "controlled burn") wikipedia.org


The maximum open air burning temperature is 260-315 °C (500-599 °F). (aka a fuel rich or "dirty burn") wikipedia.org

The situation in the towers was undeniably a "dirty burn". This is confirmed by all government reports on the World Trade Center Demolition (tms.org)

The Jet Fuel burnt off quickly and ignited office fires. journalof911studies.com

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