Noncombustible gases

Fillers that contain combined water or carbon dioxide, such as alumina trihydrate, Mg(OH)2, or dawsonite [12011 -76-6] increase fire resistance by hberating noncombustible gases when they are heated. These gases withdraw heat from the plastic and can also reduce the oxygen concentration of the air surrounding the composition. 

Inert Gas Dilution. Inert gas dilution involves the use of additives that produce large volumes of noncombustible gases when the polymer is decomposed. These gases dilute the oxygen supply to the flame or dilute the fuel concentration below the flammability limit. Metal hydroxides, metal carbonates, and some nitrogen-producing compounds function in this way as flame retardants (see Flame retardants, antimony and other inorganic compounds). 

Decomposition of the polymer becomes rapid once a certain temperature has been reached and a variety of products such as combustible tmd noncombustible gases and liquids, charred solids and smoke may also be produced. Some of these products may accelerate further decomposition whilst others may retard it and this may depend not only on the nature of the compound but also on the environmental conditions. 

Synthesis gas is a mixture of carbon monoxide, hydrogen, methane, and some noncombustible gases. A certain... 

Water gas or blue gas is essentially a mixture of combustible gases, carbon monoxide and hydrogen, associated with small amounts of the noncombustible gases, carbon dioxide and nitrogen. It is produced by alternatively admitting steam and a little air through a bed of... 

Halon is a halogenated compound that contains elements from the halogen series - fluorine, chlorine, bromine and iodine. Halogen atoms from noncombustible gases when they replace... 

It is worthwhile to emphasize that all of the available data for V-H studies have been for methane-rich gases. For heavier gases, or for noncombustible gases, there are almost no data in the V-H two-phase region the sole exception is the water content study of Song and Kobayashi (1987) for carbon dioxide. 

Dilution by noncombustible gases theories. Nonflammable gases released by the decomposition of the fire-retardant chemicals dilute the combustion gases formed by the pyrolysis of the wood and form a nonflammable gaseous mixture. 

In addition to the chemical mechanisms of fire retardants, thermal or barrier-type mechanisms may be operative. Coatings may prevent oxygen from reaching the wood surface. Dilution of combustible gases by noncombustible gases and inhibition of flaming by free radicals can also be in effect. Therefore, fire retardancy of wood involves many complex reactions. The effectiveness of a particular fire retardant depends on the overall summation of these competitive and sequential reactions and the thermal and physical environment of the material. 

Functional groups, such as cai bonyl, alcohol, halogen, and amine, yield fewer ions or none at all in a flame. In addition, the detector is insensitive toward noncombustible gases such as H2O, CO2, SO2, and NOf These properties make the flame ionization detector a most useful general detector for the analysis of most organic samples, including those that are contaminated with water and the oxides of nitrogen and sulfur. 

The diluents are noncombustible gases that reduce the heating value of the gas and are on occasion used as fillers when it is necessary to reduce the heat content of the gas. On the other hand, the contaminants are detrimental to production and transportation equipment in addition to being obnoxious pollutants. Thus the primary reason for gas refining is to remove the unwanted constituents of natural gas and to separate the gas into its various constituents. The processes are analogous to the distillation unit in a refinery where the feedstock is separated into its various constituent fractions before further processing to products. 

Class III consists of halogen-containing polymeric materials. Some of them form a small char residue, others form none at all. These polymers are inherently flame retardant because halogen radicals act as radical scavengers in the vapor phase and, therefore, inhibit combustion, as described earlier. Also the splitting-off of noncombustible gases such as HCl, Hf, and CnF, seals the polymer surface from the combustion air and is thereby partly responsible for the flame retardancy. All these factors thus influence the interaction between pyrolysis and ignition. 

Flares are often tested with noncombustible gases such as air to study flow patterns. One example is the use of smoke generators in an air-assisted flare. Another uses handheld Pitot probes (see Chapter 4) to measure velocities. For the enclosed ground flare, a video camera is used to visually observe the combustion process. A gas analysis system can be used to measure the exhaust emissions. 

Figitre 4 shows heat of combustion (in kilocalories per mole) versus m/n value for several seleeted saturated hydrocarborts. Similar resrtlts for mixtures containing selected saturated hydrocarbons and noncombustible gases are illustrated in figtrre 5. It is apparent that the heats of combustion of various gases are directly related to their corresponding m/n values. An experimental determination of m/n for the test gas is, therefore, expected to provide an on-line determination of its heat of combustion. 

Figure 3. A as a function of m/n for complex mixtures of saturated hydrocarbons and noncombustible gases. X(02> =0.

Global climate change has been identified as perhaps the most important environmental issue of this century." Greenhouse gas emissions are not exactly the same as combusted fossil fuel emissions, because several noncombustion gases can contribute to global climate change as well. For example,... 

All organic matter decomposes when burned in a hydrogen flame, and ions are generated for many organic molecules. The FID sums all chemicals contained in the sample that generated the ions in the hydrogen flame. Hame ionization detectors are insensitive toward noncombustible gases such as H2O, CO2, SO2, and NO. Therefore, these substances do not interfere with detection. Consequently, FID is quite often is coupled with a photoionization device to identify VOCs. 

Formation of the residue is considered to be a condensed-phase contribution of melamine, whereas ammonia evolution dilutes the flame with noncombustible gases. 

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