Flammability limits pressure

Air is compressed to modest pressures, typically 100 to 200 kPa ( 15-30 psig) with either a centrifugal or radial compressor, and mixed with superheated vaporized butane. Static mixers are normally employed to ensure good mixing. Butane concentrations are often limited to less than 1.7 mol 1 to stay below the lower flammable limit of butane (144). Operation of the reactor at butane concentrations below the flammable limit does not eliminate the requirement for combustion venting, and consequendy most processes use mpture disks on both the inlet and exit reactor heads. A dow diagram of the Huntsman fixed-bed maleic anhydride process is shown in Figure 1. 

The lower flammable limit (LEL) or lower explosive limit (LEL) is the minimum concentration of vapor in air below which a flame is not propagated when an ignition source is present (61—64). Below this concentration, the mixture is considered too lean to bum. The lower flammable limit and the flash point of a flammable Hquid are closely related by the Hquid s vapor pressure characteristics. 

Halothane. Halothane or Fluothane, 2-bromo-2-chloro-l,l,l-trifluoroethane [151 -67-7] is a colorless Hquid with a pleasant odor. Its lower flammability limit, 4.8% in 70% N2O/30% O2, renders it essentially nonflammable. It has a vapor pressure of 32.5 kPa (244 mm Hg) at 20 °C and is stable to soda lime. However, it is photochemicaHy reactive. 

Table 6. Flammability Limits of Carbon Monoxide in Dry Air as a Function of Temperature at Atmospheric Pressure ...

An overview of some basic mathematical techniques for data correlation is to be found herein together with background on several types of physical property correlating techniques and a road map for the use of selected methods. Methods are presented for the correlation of observed experimental data to physical properties such as critical properties, normal boiling point, molar volume, vapor pressure, heats of vaporization and fusion, heat capacity, surface tension, viscosity, thermal conductivity, acentric factor, flammability limits, enthalpy of formation, Gibbs energy, entropy, activity coefficients, Henry s constant, octanol—water partition coefficients, diffusion coefficients, virial coefficients, chemical reactivity, and toxicological parameters. 

An alternate method for flash point prediction is the method of Gmehling and Rasmussen and depends on the lower flammabihty limit (discussed later). Vapor pressure as a function of temperature is also required. The method is generally not as accurate as the preceding method as flammability limit errors are propagated. The authors have also extended the method to defined mixtures of organics. 

Flammable Limits Flammable limits, or the flammable range, are the upper and lower concentrations (in volume percent) which can just be ignited by an ignition source. Above the upper limit and below the lower hmit no ignition will occur. Data are normally reported at atmospheric pressure and at a specified temperature. Flammable hm-its may be reported for atmospheres other than air and at pressures other than atmospheric. 

TABLE 26-10 Flammability Limits, Autoignition Temperature, and Flash Points of Selected Substances in Air at Atmospheric Pressure... 

Volatile Solids, NFPA 325, Quincy, Mass.). Pressure particularly affects flash point and the uppei flammable limit (UFL) see later section entitled Effect of Temperature, Pressure, and Owgen. Mists of high-flash-point liquids may be flammable the lowei flammable limit (LFL) of fine mists and accompanying vapor is about 48 g/m of air, basis 0°C and 1 atm (0.048 oz/fP). 

Effect of Temperature Pressure and Oxygen LFLs and LOCs at 1 atm decrease about 8 percent of their values at near normal room temperature for each 100°C increase. Upper flammable limits increase approximately 8 percent for the same conditions. 

For apphcation of Eq. (26-48), x should not exceed 300 m (984 ft). The reason for selec ting 100 percent, instead of the upper flammable limit (UFL), in the equation for Vj is that in an incipient explosion vapor above the UFL may be mixed with additional air and, thereby, contribute to explosion pressure. 

Flammability information Flash point Fire point Flammable limits (LEL, UEL) Ignition temperature Spontaneous heating Toxic thermal degradation products Vapour pressure Dielectric constant Electrical resistivity Electrical group Explosion properties of dust in a fire... 

LEL (lower explosive, OR FLAMMABLE, LIMIT) The minimum eoneentration of a gas, vapour, mist or dust in air at a given pressure and temperature that will propagate a flame when exposed to an effieient ignition souree. Generally expressed as % by volume for gases and vapours, and as mg/m for mists or dusts. 

Ignition temp. (°C) Flammable limits (%) Boiling point (°C) Melting point (°C) Solubility in water (g/100 g) Vapour pressure (mm Hg/°C)... 

Fire Hazards - Flash Point Not flammable Flammable Limits in Air (%) Not flammable Fire Extinguishing Agents Not pertinent Fire Extinguishing Agents Not To Be Used Not pertinent Special Hazards of Combustion Products Not pertinent Behavior in Fire Pressurized containers may explode and release toxic and irritating vapors Ignition Tenperature Not pertinent Electrical Hazard Not pertinent Bunting Rate Not pertinent. 

Pressure Safety Design Practices Estimating Lower Flammable Limits... 

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