Methane ignition temperature

Figure 7.1-1. Compressed methane/air mixtures. Left, pressure dependence of the upper flammability limit v, 20°C X, 100°C o, 200°C right, ignition temperatures, methane/oxygen (mol/mol) X, stoichiometric methane/air (mol/mol) 0,1/1 v, 1/2 , 1/3.

Gaseous fuels containing fractions whose ignition temperature is lower than that of methane may require the use of low-compression heads and a resulting derating of the gas engine. 

GP 8] [R 7] Ignition occurs at a rhodium catalyst at catalyst temperatures between 550 and 700 °C, depending on the process parameters [3]. Total oxidation to water and carbon dioxide is favored at low conversion (< 10%) prior to ignition. Once ignited, the methane conversion increases and hence the catalyst temperature increases abruptly. 

The results of the catalytic activity for methane combustion are summarised in Table 1 and fig. 1. The methane conversions of the Pd2HZSHe catalyst are higher than those of the Pd2HZIHe sample. In fact, the ignition temperatures T10% (temperature necessary to have 10% of methane conversion) are respectively 355 and 371°C. This result suggests that the catalyst prepared by solid-exchange method is more active than that prepared by impregnation. 

Furthermore, no significant differences are observed on the methane conversion or on the ignition temperatures of the Pd2HZSHe and the Pd2HZS02 catalysts. This result presumes that the catalyst pre-treatment with oxidant or with inert gas has the same effect on the activity of the Pd-HZSM-5 catalysts prepared by the solid-exchange method. Moreover, a noticeable methane conversion increase is observed when the NaZSM-5 support is used instead of the HZSM-5 zeolite. The ignition temperatures... 

T10%) are respectively 355 and 285°C. Finally, the increase of the designed palladium loading from 0.5 to 2 % is observed to increase the methane conversion. The ignition temperatures are 350, 320 and 285°C respectively for the Pdo.sNaZS02, the PdiNaZS02 and the Pd2NaZS02 catalysts. 

The simplest of the ethers would be ether that has the simplest hydrocarbon backbones attached those backbones are the radicals of the simplest hydrocarbon, methane. Therefore, the simplest of the ethers is dimethyl ether, whose formula is CH3OCH3. Dimethyl is used because there are two methyl radicals, and "di-" is the prefix for two. This compound could also be called methyl methyl ether, or just plain methyl ether, but it is better known as dimethyl ether. It is an easily liquified gas that is extremely flammable, has a relatively low ignition temperature of 66°F, and is used as a solvent, a refrigerant, a propellant for sprays, and a polymerization stabilizer. 

Sulphur dust is more dangerous than coal-dust, because of the low ignition temperature of sulphur suspensions in air. According to Dubnov [53] 100 g charges of the U.S.S.R. explosives Ammonit No. 1 and 8 ignited sulphur dust. The same explosives did not ignite a methane-air mixture when the quantities were 400 and 500-650 g respectively. In sulphur mines explosives of very low detonation temperature should be used. 

Dubnov examined the effect of various salts on the ignition temperature and on the explosion lag of methane-air mixtures (Table 103). 

The ignition temperatures of the most important gaseous components of the explosion products (H2, CO and CH4) in methane-air mixtures lie within the following limits ... 

For CO, reforming of methane. KIT-1 performed better than Al20, or La,0 as support. Ni/KIT-1 co-impregnated with 3 wt% Ca lasted 20 h without deactivation, and CO, and methane conversions close to the thermodynamic equilibrium were obtained. According to TG/DTA. coke formed during a given reaction increased in the order of Ni/Ca/KIT-1 < Ni/K1T-1 < Ni/Al,0, < ICI 46-1. Methane combustion study showed the activity pattern of Pd/KIT-1 > Pd/MCM-41. Pd/HMS > Pd/Al,0, > Pd/SiO,. MIBK combustion experiment demonstrated that catalyst ignition temperature can be lowered by ca. 30-35 °C when Pt was supported on KIT-1. MCM-41. MCM-48 and HMS produced similar results. 

When gases from the reactor or the high-pressure separator are discharged through the chimney into the air, explosive mixtures can be formed. The explosion limits of mixtures of ethylene with air, as well as methane, hydrogen, and vinyl acetate with air are listed in Table 7.2-1 together with the ignition temperature. 

It has been reported 52) that addition of 10% methane to a carbon monoxide-oxygen mixture raises the ignition temperature by 100° C. However, the limits for carbon monoxide-oxygen and methane-oxygen lie in about the same temperature range. A similar inhibition of the second limit of hydrogen-oxygen by ethane has been observed (6, 7). 

Raimondeau et al. [74] modeled the homogeneous high-temperature combustion of a preheated stoichiometric mixture of methane and air at a flow rate of 2 m s 1 and a reference temperature of1 000 °C, which corresponds to the methane ignition temperature under these conditions. Fora channel of 100 pm diameter, no gradients of species concentration and temperature were determined by the calculations. It was demonstrated that temperature losses through the wall lead to flame extinction, which was more pronounced with decreasing channel diameter. 

Despite the high ignition temperature of methane-air mixtures of 595°C/650°C (see Table 1.3), the maximum surface temperature is subjected to a very strong limitation with respect to the unavoidable presence of coal dust with relatively low glow temperatures (see Table 1.4)... 

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