Ignition autoignition temperature

Fuel LHV HHV (MJ/kg) (MJ/kg) Stoichiometric Air/Fuel Ratio (kg) Combustible Range(%) Min. Flame Ignition Autoignition Temperature (°C) Energy (MJ) Temperature (°C) ... 

The autoignition temperature of a substance is the lowest temperature at which a solid, liquid, or gas will spontaneously ignite resulting in self-sustained combustion without the need for an external ignition source. A material released from a process above its autoignition temperature will ignite. Autoignition temperatures of some common materials are shown in Table B-2. 

Flammable liquid flash point (closed cup) 4.4°C (40°F) vapor pressure 28 torr at 25°C (77°F) vapor density 3.17 (air = 1) the vapor is heavier than air and may cause a flashback fire hazard in the presence of a source of ignition autoignition temperature 536°C (997°F) fire-extinguishing agent dry chemical, foam, or CO2 use a water spray to keep fire-exposed confainers cool. 

Ignition (autoignition) temperature - This is the minimum temperature which will initiate a self-sustained combustion independent of the heat source. 

Autoignition temperature. The autoignition temperature of a material is the temperature at which it will ignite spontaneously in air without any external source of ignition. 

Combustion of a flammable gas-air mixture occurs if the composition of the mixture lies in the flammable range and if there is a source of ignition. Alternatively, combustion of the mixture occurs without a source of ignition if the mixture is heated up to its autoignition temperature. 

The autoignition temperature is the minimum temperature required for self-sustained combustion in the absence of an external ignition source. The value depends on specified test conditions. Tht flammable (explosive) limits specify the range of concentration of the vapor in air (in percent by volume) for which a flame can propagate. Below the lower flammable limit, the gas mixture is too lean to burn above the flammable limit, the mixture is too rich. Additional compounds can be found in National Fire Protection Association, National Fire Protection Handbook, 14th ed., 1991. 

Flash points and autoignition temperatures are given in Table 11. The vapor can travel along the ground to an ignition source. In the event of fire, foam, carbon dioxide, and dry chemical are preferred extinguishers. The lower and upper explosion limits are 1% and 7%. 

Some of the tests and criterion used to define fire resistance may be found in the Hterature (9). Additionally, the compression—ignition and hot manifold tests as defined in MIL-H-19457 and MIL-H-5606, respectively the Wick test as defined by Federal Standards 791, Method 352 flash point and fire point as defined in ASTM D92 autoignition temperature as defined in ASTM D2155 and linear flame propagation rate are defined in ASTM D5306 are used. 

Direct-Flame Incinerators. In direct-flame incineration, the waste gases are heated in a fuel-fired refractory-lined chamber to the autoignition temperature where oxidation occurs with or without a visible flame. A fuel flame aids mixing and ignition. Excess oxygen is required, because incomplete oxidation produces aldehydes, organic acids, carbon monoxide, carbon soot, and other undesirable materials. 

The ignition temperature or autoignition temperature is the minimum temperature of a flammable mixture that is required to initiate or cause self-sustained combustion without ignition from an external source of energy such as a spark or flame (ASTM D2155). 

The low autoignition temperature of benzaldehyde (192°C) presents safety problems since benzaldehyde can be ignited by exposure to low pressure steam piping, for example. Benzaldehyde may also spontaneously ignite when soaked into rags or clothing or adsorbed onto activated carbon (13). 

Catalysts such as iron oxides cause isomeriza tion of the ethylene oxide to acetaldehyde with the evolution of heat. The acetaldehyde has a much lower autoignition temperature in air than does ethylene oxide, and the two effects may lead to hot-spot ignition (190,191). 

As a guide, because of convection that occurs from hot surfaces, ignition by a hot surface in open air should not be assumed unless the surface temperature is at least 200°C above the published minimum autoignition temperature (American Petroleum Institute, Ignition Risk of Hot Sui faces, API PSD 2216, Washington, 1980). 

Materials having low minimum spark ignition energies, or autoignition temperatures... 

Autoignition Temperature (AIT) The auto ignition temperature of a substanee, whether solid, liquid, or gaseous, is the minimum temperature required to initiate or eause self-sustained eombustion, in air, with no other souree of ignition. 

A material that is above its autoignition temperature will ignite spontaneously on contact with air in the correct proportions (see Table 6.1 for minimum temperature of ignition source). 

Important flammability characteristics are the lower and upper flammability limits, the flash point, the minimum ignition energy, the minimum oxygen concentration, and the autoignition temperature. Values of some of these properties are published for many compounds (NFPA, 1994). These numbers have typically been developed under standardized test conditions. Process conditions may influence their values. 

Before the size of the flammable portion of a vapor cloud can be calculated, the flammability limits of the fuel must be known. Flanunability limits of flammable gases and vapors in air have been published elsewhere, for example, Nabert and Schon (1963), Coward and Jones (1952), Zabetakis (1965), and Kuchta (1985). A summary of results is presented in Table 3.1, which also presents autoignition temperatures and laminar burning velocities referred to during the discussion of the basic concepts of ignition and deflagration. 

The niaxiinwn spontaneous ignition temperature (SIT) or autoignition temperature (AIT) is defined as die minimum temperature at wliicli combustion occurs in a bulk gas mixture when die temperature of a flaiiunable gas-air mixture is raised in a unifonidy heated apparatus. The autoignidon temperature represents... 

Inspection of the numerical solutions of the equations shows that, with the exception of Es= 0 kcal/mole, the rate of surface temperature increase with time is very large once the surface temperature reaches approximately 420°K—on the order of 108°K/sec. Because typical autoignition temperatures are of the order of 625°K for composite propellants, the particular value of the ignition temperature does not affect the computed numerical value of the ignition-delay time. 

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