Combustible volatiles, evaporation

If combustible volatiles are evaporating from the load, NFPA standards require that the atmosphere in the oven never exceed one-fourth or one-half (depending on the control system) of the lower explosive limit of the volatile gas. For noncombustable volatiles, the required volume for circulation is less severe, but based upon the ability of the circulating stream to absorb the vapor. If the vapor is water, humidity sensors should be used to automatically adjust burner input, circulated volume, and/or exhaust damper. If humidity is not a sensitive factor, simple temperature controls will suffice. 

Liquid fuels. Industrial burners for liquid fuels usually atomize the fuels in hot air so that droplets will evaporate during combustion. For more volatile fuels such as kerosine, vaporizing burners of various types are employed, usually for domestic purposes. 

Thermal insulation (or lagging) on plant equipment may become soaked or impregnated witli oils and otlier flanuiuible liquids. When the lagging gets hot, spontaneous combustion can occur. Lagging fires are affected by oil laiks, insulation material, and temperature. Spontaneous combustion occurs only when tlie oil is nonvolatile, since volatile oil evaporates more easily, tlius delaying tlie... 

Gas may be formed by microbiological degradation of organics, evaporation and volatilization of volatile materials, or chemical reactions. The high combustibility of methane—a major component of landfill-generated gas—is a potential hazard. The emission of gas can be accelerated by elevated temperatures and venting conditions. Air pollution, which may result from gaseous... 

As for all of the fractions of organic material in seawater, the volatile organic carbon fraction is defined by the method by which it is collected. In one of the earliest estimates, Skopintsev [93] defined the volatile fraction as the difference between total organic carbon values, as measured by evaporation and dry combustion, when the evaporations were carried out at room temperature and at 60 °C. Thus Skopintsev s volatile fraction consists of those compounds that are volatile from acidified solution taken to dryness at 60 °C but not at 20 °C. This fraction was found to be between 10 and 15% of the total organic carbon. He also noted a 15% difference in measured organic carbon with his dry combustion method when samples were dried at different temperatures and concluded that this difference was due to the loss of volatiles. 

Gershey et al. [58] have pointed out that persulfate and photo-oxidation procedures will determine only that portion of the volatile organics not lost during the removal of inorganic carbonate [30,79,92,181]. Loss of the volatile fraction may be reduced by use of a modified decarbonation procedure such as one based on diffusion [98]. Dry combustion techniques that use freeze-drying or evaporation will result in the complete loss of the volatile fraction [72,79, 92,93],... 

Fuel asphaltenes, resins, and other heavy compounds can build up as residues on engine components after evaporation and burning away of the more volatile fuel components. These residues can accumulate as deposits which may interfere with heat transfer, lubrication, and efficient fuel combustion. 

Fuel volatility is an extremely important factor related to fuel combustion and burning efficiency. Evaporation, vaporization, and vapor pressure of fuel can all be reduced in cold environments. Poor startability and warmup of gasoline and diesel engines can be directly related to fuel volatility. Also, cold kerosene will not vaporize and bum as efficiently in wick-fed systems. 

Knock can occur over the entire range of engine speed. During acceleration, a large volume of fuel enters the intake manifold and mixes with air. Vaporization and evaporation of the more volatile, low-octane compounds occurs readily. These compounds enter the combustion chamber and detonate quickly to initiate knock. The higher-octane, less-volatile compounds do not vaporize as rapidly from the fuel volume. See FIGURE 5-5 for fuel combustion chamber abnormalities. 

As is known, Belyaev [1] used convincing arguments to prove that in the combustion of volatile secondary explosive materials the explosive material is first heated to the boiling temperature, then evaporates, and the vapors of the explosive material enter into chemical reaction after further heating. 

Mists are dust clouds in which the particles happen to be liquid. Should that liquid be combustible, even though it is nowhere near its flash-point, explosion is possible [1] [2]. Mist explosions attract increasing study [3]. It is possible that many vapour cloud explosions have had a mist component. The editor surmises that, under appropriate circumstances, evaporation of volatile mist by the heat of a vapour (or mist) explosion might generate a larger pressure pulse than simple thermobaric effects on air. Foams are inverse mists and should show similar explosive potential. 

In MEIS there is no need to describe the process of volatiles burning. Their preset composition is limited by the dimension of vector x, and can be increased to several hundreds of components, which virtually does not affect model complexity but somewhat increases the time of calculations. The results obtained allow the estimation and withdrawal from the vector x of the components of low impact on the calculation results. In the calculations we used 68 chemical components. In the kinetic model uncertainty in the composition of volatile substances makes it impossible to describe in detail their combustion based on the elementary kinetics. The description in this case should also include processes of evaporation from the particle surface and diffusion. As a rule the parameters of these processes are unknown as well. 

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