Minimum ignition temperature

The most important polyhydric alcohols are shown in Figure 1. Each is a white soHd, ranging from the crystalline pentaerythritols to the waxy trimethylol alkyls. The trihydric alcohols are very soluble in water, as is ditrimethylol-propane. Pentaerythritol is moderately soluble and dipentaerythritol and tripen taerythritol are less soluble. Table 1 Hsts the physical properties of these alcohols. Pentaerythritol and trimethyl olpropane have no known toxic or irritating effects (1,2). Finely powdered pentaerythritol, however, may form explosive dust clouds at concentrations above 30 g/m in air. The minimum ignition temperature is 450°C (3). 

Viayl fluoride is flammable ia air between the limits of 2.6 and 22% by volume. Minimum ignition temperature for VF and air mixtures is 400°C. A small amount, <0.2%, of terpenes is added to VF to prevent spontaneous polymerization. The U.S. Department of Transportation has classified the inhibited VF as a flammable gas. 

Volume of vessel (free volume V) Shape of vessel (area and aspect ratio) Type of dust cloud distribution (ISO method/pneumatic-loading method) Dust explosihility characteristics Maximum explosion overpressure P ax Maximum explosion constant K ax Minimum ignition temperature MIT Type of explosion suppressant and its suppression efficiency Type of HRD suppressors number and free volume of HRD suppressors and the outlet diameter and valve opening time Suppressant charge and propelling agent pressure Fittings elbow and/or stub pipe and type of nozzle Type of explosion detector(s) dynamic or threshold pressure, UV or IR radiation, effective system activation overpressure Hardware deployment location of HRD suppressor(s) on vessel... 

Maintain inlet temperature of heating medium sufficiently below the minimum ignition temperature... 

Dust Minimum ignition temperature (°C) Minimum explosible concentration (g/l)... 

Dost Minimum ignition temperature (°C) Minimum explosible concentration (g/l) Minimum ignition energy (m)) Maximum explosion pressure Maximum rate of pressure rise (psi/s) Maximum Notes oxygen cor>centration to prevent ignition (% by volume)... 

For processes under development, the most cost-effective means of avoiding potential risk is to eliminate those materials that are inherently unsafe that is, those materials whose physical or physico-chemical properties lead to them being highly reactive or unstable. This is somewhat difficult to achieve for several reasons. First, without a full battery of tests to determine, for example, flammability, upper/lower explosivity limits and their variation with scale, minimum ignition temperatures, and so on, it is almost impossible to tell how a particular chemical will behave in a given process. Second, chemical instability may make a compound attractive to use because its inherent reactivity ensures a reaction proceeds to completion at a rapid enough rate to be useful that is, the reaction is kinetically and thermodynamically favoured. 

Minimum ignition temperature of a dust. The minimum ignition temperature of a dust is the lowest temperature at... 

The tangent indicated at point B also represents a critical reaction condition, but of a somewhat different type. In this case the reactor temperature corresponding to point B represents the minimum temperature at which autoignition will occur. In this sense it can be regarded as a minimum ignition temperature. Like the critical extinction point, this temperature should not be regarded as an absolute value but as a function of various operating parameters. 

Table V. Effect of Metal Ions on the Minimum Ignition Temperature (in Oxygen) of Cottonwood Chars...

Samole Minimum Ignition Temperature rc) Ignition Temperature of Chemisorbed Charsb( C)... 

Minimum ignition temperature of a dust cloud (MITc) The lowest temperature of a hot surface on which the most ignitable mixture of the dust with air is ignited under specified test conditions. 

Flammable gas or vapor-air mixtures Due to their low minimum ignition energies (<1 mj), avoidance of effective ignition sources in flammable gas or vapor-air mixtures is in principle possible only in exceptional cases. For hot surfaces a maximum permissible surface temperature Tmax must be specified, with the help of the minimum ignition temperature (MIT) of flammable gases, vapors, or liquids, so that the temperature of all surfaces is not exceeded (Table 23-8). 

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