Methane explosion limits

Many polymer films, eg, polyethylene and polyacrylonitrile, are permeable to carbon tetrachloride vapor (1). Carbon tetrachloride vapor affects the explosion limits of several gaseous mixtures, eg, air-hydrogen and air-methane. The extinctive effect that carbon tetrachloride has on a flame, mainly because of its cooling action, is derived from its high thermal capacity (2). 

The composition of the gas mixture, which is introduced into the tube bundle reactor (tubes of 6-12 m length and 20-50 mm diameter, filled with the Ag catalyst) consists of 15-50 vol % ethylene, 5-9% oxygen, as much as 60% methane as dilution gas, and 10-15% carbon dioxide. The reaction therefore proceeds above the upper explosion limit. The ethylene conversion runs up to 10% per cycle through the reactor. The ethylene oxide selectivity amounts to 75-83 % maximum. The formed ethylene oxide is recovered by scrubbing with water and the newly formed carbon dioxide is separated from the cycle gas, e.g., by hot potash washing process. 

Ethylene oxide is produced by adding ethylene, oxygen, a methane diluent, and recycled carbon dioxide to a continuous reactor. Gaseous compositions are controlled carefully to keep the concentrations outside the explosion limits. 

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. 

In some applications, it is necessary to inject nutrients or other chemicals into the aquifer to effect a more efficient restoration. Most of the time, additives are injected into separate wells. These additives may include surfactants, nutrients, pH adjustment chemicals, or additional carbon sources. Some success has been achieved with injected heated air to improve volatility of the chemicals. Where a small quantity of methane (as a primary substrate) is required, it can be added with the injection air. The lower explosive limit (LEL) of methane in air is 5% thus, extreme care must be used to control the mixture and the methane content of the vapor that reaches the surface. 

ZhFizKhim 5, 1459(1934) (Detonation in gaseous mixtures. Variation of the detonation wave velocity with pressure) 6) M.A. Rivin A.S. Sokolik, ZhFizKhim 7, 571 (1936) (The explosion limits of gaseous mixtures. Expln limits of hydrogen-air mixtures) 7) Ibid, 8, 767(1936) (Expln limits in carbon monoxide-methane mixts)... 

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 would seem worth while, therefore to restudy the explosion limits of methane-oxygen and ethane-oxygen and also to study the effects of these hydrocarbons on the carbon monoxide-oxygen limits, with a view toward establishing whether these systems are connected in any way. In any case, valuable clues to the mechanisms of combustion of hydrocarbons can probably be obtained. 

Contact of acetylene with the cone, acid in presence of mercury salts forms trinitro-methane, explosive above its m.p., 15°C. Subsequent addition of sulfuric acid produces tetranitromethane, a powerful oxidant of limited stability, in high yield. 

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. 

The theoretical air required for the oxidation of toluene to benzoic add, 1.5 mols of oxygen per mol of tolnene, amounts to about 30 cn. ft. of air measured at 20° C. (6S° F.) and one atmosphere, per pound of toluene oxidized. Similarly, the theoretical air for oxidation to bcnzalcle-hyde amounts to 20 cu. ft. per pound of tolnene oxidized. The explosive limits of toluene at ordinary pressures and temperatures as measured in narrow tubes or small vessels are lower limit, 0.003375 lbs. toluene per cu. ft. air (296.5 cu. ft. air per lb. toluene) and upper limit, 0.01927 lbs. toluene per cu. ft. air (52 cu. ft. air per lb. toluene).1151 In the case of the lower aliphatic hydrocarbons as methane and ethane it is well known that the explosive or inflammability limits widen with rise in temperature so that it could well be expected that mixtures of toluene and air leaner than the one given for the lower limit and richer than the one for the upper limit would become inflammable as the temperature becomes higher. The same is true for increase in size of the explosion chamber. Hence, although theoretical mixtures of toluene and air for formation of benzaldehyde and benzoic acid lie on the rich side of the inflammable range,... 

N,N DIMETHYL BENZENE METHAN-AMINE (103-83-3) CsH.jN Combustible liquid [explosion limits in air (vol %) 0.9 to... 

ETHER, VINYL ETHYL (109-92-2) C4HgO Highly flammable, polymerizable liquid. Forms explosive mixture with air [explosion limits in air (vol %) 1.7 to 28 flash point <-50°F/<-46°C autoignition tenqj 395°F/202°C Fire Rating 4]. Forms unstable peroxides on contact with air. Reacts violently with oxidizers, ammonium persulfate, bromine dioxide, methane sulfonic acid (may cause polymerization), nitric acid, perchlorates, permanganates, peroxides and hydroperoxides, sulfuric acid. Incompatible with acids, ammonia, aliphatic amines, alkanolamines. On small fires, use dry chemical powder (such as Purple-K-Powder), alcohol-resistant foam, or COj extinguishers. 

PHENYL METHANE (108-88-3) CtH, CjHsCHj Forms explosive mixture with air [explosion limits in air (vol %) 1.4 to 6.7 flash point 39°F/4°C cc autoignition temp 896°F/480°C Fire Rating 3]. Violent reaction with strong oxidizers, bromine, bromine trifluoride, chlorine, hydrochloric acid-sulfuric acid mixture, l,3-dichloro-5,5-dimethyl-2,4-imidazolididione, dinitrogen tetraoxide, fluorine, nitric acid (cone.). 

SULFICYLBIS (METHANE) (67-68-5) CjHjOS (CH3)2S0 Combustible liquid [explosion limits in air (vol %) 2.6 to 63.0 flashpoint 203°F/95°C oc autoignition temp 419°F/215°C Fire Rating 2]. Violent or explosive reaction with strong oxidizers, acryl halides, aryl halides and related compounds, alkali metals p-bromobenzoyl acetanilide, boron compounds, especially hydrides iodine pentafluoride, magnesium perchlorate, methyl bromide, perchloric acid, periodic acid, silver fluoride, sodium hydride, potassium permanganate. Forms powerfully explosive mixtures with metal salts of oxoacids [iron(III)nitrate, phosphonic acid, sodium perchlorate]. On small fires, use dry chemicals or COj extinguishers. 

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