Methane lower flammability limit

For example, the lower flammability limit of methane in air at sea level is a concentration (by volume or partial pressure) of about 5%. The upper flammability limit is about 15% by volume or partial pressure. Heavier hydrocarbons tend to have lower LFLs. The LFL and UFL of some common hydrocarbons are given in Table B-2. 

A mixture of methane and air is capable of being ignited only if the mole percent of methane is between 5% and 15%. A mixture containing 9.0 mo e% methane in air flowing at a rate of 700. kg/h is to be diluted with pure air to reduce the methane concentration to the lower flammability limit. Calculate the required flow rate of air in mol/h and the percent by mass of oxygen in the product gas. Note Air may be taken to consist of 21 mole% O2 and 79% N2 and to have an average molecular weight of 29.0.)... 

For example, the stoichiometric percentage of methane in a methane-air mixture is 9.5 mole%. (Prove it.) Experimentally, it is found that the lower flammability limit of CH4-air mixtures at 1 aim is approximately 5% CH4 and the upper flammability limit is approximately 15% CH4. Thus, a CH4-air mixture containing between 5% CH4 and 15% CH4 must be considered a fire or explosion hazard, while a mixture containing 3% CH4 may be considered safe, and a mixture containing 18% CH4 may also be considered safe as long as it is not brought into contact with additional oxygen. 

A gas mixture of methane, ethane, and pentane entering an adsorber has an upper flammability limit of 12.5% and a lower flammability limit of 2.85%. Given a methane concentration of 30%, calculate the concentrations of the other two components of the gas mixture. Flammability limits for methane, ethane, and propane at various concentrations are given in the following table. 

The lower flammability limits for benzene, methanol and methane are 1.4, 6.0 and... 

Hydrocarbons, such as LNG or LPG, are generally flammable in air over limited composition ranges. For example, methane is only flammable with compositions from 5 and 15 % by volume of methane in air. The density of methane gas is about one half that of air, so the vapour from LNG rises rapidly, mixes by convection with the air and quickly dilutes to below the lower flammability limit of 5 % while dispersing upwards and away from ignition sources. 

A methane leak in a closed room is assumed to mix uniformly with air in the room. The room is (4 x 4 x 2.5)m high. Take the air density as 1.1 kg/m3 with an average molecular weight of 29 g/g mole. How many grams of methane must be added to make the room gases flammable The lower and upper flammability limits of methane are 5 and 15 % by volume respectively. 

They are sensitive to all flammable gases, and they give approximately the same response to the presence of the lower explosive limit (LEL) concentrations of all the common hydrocarbon gases and vapors. However it should be remembered that gas detectors do not respond equally to different combustible gases. The milli-volt signal output of a typical catalytic detector for hexane or xylene is roughly one half the signal output for methane. 

Almost any flammable mixture will, under favorable conditions of confinement, support an explosive flame propagation or even a detonation. When a fuel-oxidant mixture of a composition favorable for high-speed combustion is weakened by dilution with an oxidant, fuel, or an inert substance, it will first lose its capacity to detonate. Further dilution will then cause it to lose its capacity to burn explosively. Eventually, the lower or upper flammability limits will be reached and the mixture will not maintain its combustion temperature and will automatically extinguish itself. These principles apply to the combustible cryogens hydrogen and methane. The flammability and detonability... 

Methane is highly flammable and is therefore an explosion and fire hazard the lower explosive limit is 5-15% by volume. Extreme care must be taken to keep areas of high concentration free from ignition sources, such as sparks from static electricity. Explosion-proof equipment should be used in these areas. Many people believe that methane is an important greenhouse gas, and that the apparent threefold increase in atmospheric concentrations over the last 200 years affects the stratospheric ozone layer and the oxidizing capacity of the atmosphere. 

There are two composition limits of flammability for air and a gaseous fuel under specified conditions [76]. The lower limit is the minimum concentration of combustible gas that will support combustion, while the higher limit is the maximum concentration. Table 5.1 shows the lower and higher limits for pure hydrocarbons in air at room temperature and atmospheric pressure (RTP) [76]. For methane in air, the flammability limit is 5—15 mol%. For ethane in air, the limits are 2.9—13.0 mol%. The limits become lower with increasing molecular weight. It also is interesting to note that the limits are the same for n-pentane and isopentane, and also for -butane and isobutane. 

In considering issues related to combustion, malodor, or toxicity or chemical reactions, one generally requires (at least) the one-point probability density function. For example, the probability of ignition (PI) of, say, a methane gas cloud is given by the probability that, at a position located by vector x at time t, concentrations between the lower 0 and upper 0 flammability limits are encountered. That is. 

Declassification to potentially gassy operations. Underground construction gassy operations may be declassified to Potentially Gassy when air monitoring results remain under 10 percent of the lower explosive limit for methane or other flammable gases for three consecutive days. 

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