Explosive limits lower limit

Explosive limits Lower limit Upper limit 0.9% 6% McDermott 1975... 

Lower explosive limit Lower limit of flammability or explosibihty of a gas or vapor at ordinary ambient temperatures expressed in percent of the gas vapor in air by volume. Tests for comparative flammability of liquids, UI 340. Laboratories Incorporated Underwriters, New York, 1997. 

LEL/LFL Lower Explosive Limit/Lower Flammable Limit... 

Tlie remainder of tliis cliapter provides information on relative physical properties of materials (flash points, upper and lower explosive limits, tlireshold limit values, etc.) and metliods to calculate tlie conditions tliat approach or are conducive to liazardous levels. Fire liazards in industrial plants are covered in Sections 7.2 and 7.3, and Sections 7.4 and 7.5 focus on accidental explosions. Sections 7.6 and 7.7 address toxic emissions and liazardous spills respectively. tliese latter types of accident frequently result in fires and explosions tliey can cause deatlis, serious injuries and financial losses. 

Explosive limits upper limits, 95% lower, 2% by volume in air (American Conference of Governmental Industrial Hygienists, 1991)... 

Explosive limits Lower explosive limit 0.5% at 236 °C NIOSH 1997... 

Explosion hazards develop as flammable vapors accumulate to a concentration that is within their flammable limits = explosion limits = lower explosive limit (LEL) and upper explosive limit (UEL). (See chap. 7 of reference 47, and reference 48.) Most codes and standards require built-in air dilution to keep the furnace atmosphere below one-fourth of the LEL, or one-half LEL with specific automatic control or alarm arrangements. The dilution changestemperature and mass transfer potentials (discussed later), and increases the convection velocity. 

In systems that contain some oxygen, operators may limit the acceptable concentration of petroleum hydrocarbons in the feed (to approximately 1 to 3%) in order to keep the contaminant concentrations in the vapors below the lower explosive limit. This limit can be met by blending soils. 

Reagent Dilution/Cairier Gas Requirements Diluted with water to 5-25% concentration. Air is the carrier gas. (Steam is no longer used.) Typically, 4 scfm of plant air per injector is currently used for atomization and for injector cooling. Not diluted with water. Air or steam at 1-2% of the flue gas flow rate is the carrier gas. This gas requirement is reduced by the amount of water vaporized if aqueous ammonia is vaporized. Not diluted with water. Carrier gas is air, flue gas, or possibly steam at about 2 psig. Ammonia/carrier gas volumetric ratio is a minimum of about 1 to 20 for anhydrous ammonia to keep the ammonia concentration in the air below the lower explosive limit. Lower concenuations may be used based on injection diffusion patterns, the ammonia vaporization heat requirement, minimum flow control ranges, and other factors. 

Explosive limit - lower (%) Explosive limit - upper (%) Vapor pressure Vapor density Relative density Solubility(ies)... 

Odor Characteristic Characteristic Characteristic and detectable at cone. > 20% lower explosive limit (NF EN 589, Appendix A)... 

The autoignition temperature is the minimum temperature required for self-sustained combustion in the absence of an external ignition source. The value depends on specified test conditions. Tht flammable (explosive) limits specify the range of concentration of the vapor in air (in percent by volume) for which a flame can propagate. Below the lower flammable limit, the gas mixture is too lean to burn above the flammable limit, the mixture is too rich. Additional compounds can be found in National Fire Protection Association, National Fire Protection Handbook, 14th ed., 1991. 

Flash points and autoignition temperatures are given in Table 11. The vapor can travel along the ground to an ignition source. In the event of fire, foam, carbon dioxide, and dry chemical are preferred extinguishers. The lower and upper explosion limits are 1% and 7%. 

Flammability Acrolein is very flammable its flash point is <0° C, but a toxic vapor cloud will develop before a flammable one. The flammable limits in air are 2.8% and 31.0% lower and upper explosive limits, respectively by volume. Acrolein is only partly soluble in water and will cause a floating fire, so alcohol type foam should be used in firefighting. The vapors are heavier than air and can travel along the ground and flash back from an ignition source. 

The relatively low flash points of some acrylates create a fire hazard. Also, the ease of polymerization must be home in mind in ah. operations. The lower and upper explosive limits for methyl acrylate are 2.8 and 25 vol %, respectively. Corresponding limits for ethyl acrylate are 1.8 vol % and saturation, respectively. All possible sources of ignition of monomers must be eliininated. 

The explosive limits of hydrazine in air are 4.7—100 vol %, the upper limit (100 vol %) indicating that hydrazine vapor is self-explosive. Decomposition can be touched off by catalytic surfaces. The presence of inert gases significantly raises the lower explosive limit (10) (Table 2). 

Table 2. Lower Explosive Limits of Hydrazine in Other Gases...

Undesirable combustible gases and vapors can be destroyed by heating to the autoignition temperature in the presence of sufficient oxygen to ensure complete oxidation to CO2 and H2O. Gas incinerators are appHed to streams that are high energy, eg, pentane, or are too dilute to support combustion by themselves. The gas composition is limited typicaUy to 25% or less of the lower explosive limit. Gases that are sufficiendy concentrated to support... 

Isoprene is classified by the ICC as a flammable Hquid requiring a red label (124). Its flash point is —54°C with a lower explosive limit (LEL) of 1.5%... 

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