Flammability of gas mixtures Part 2: Influence of inert gases
ABSTRACT Ternary systems, which contain flammable gas, inert gas and air, were studied in order to give the user an evaluation of the ISO 10156 calculation method for the flammability of gas mixtures. While in Part 1 of this article the fire potential of flammable gases was the focal point, the influence of inert gases on the flammability of gas mixtures was studied in Part 2. The inerting capacity of an inert gas is expressed by the dimensionless K value, the so-called "coefficient of nitrogen equivalency". The experimental determination of K values is demonstrated by using explosion diagrams. The objective of this study was to compare the estimated results, given by ISO 10156, with measurements of explosion ranges based on the German standard DIN 51649-1, given by CERN and CHEMSAFE. The comparison shows that ISO 10156, Table 1, supplies conservative K values, which can be regarded as safe in all cases. Nevertheless, in a number of cases ISO underestimates the inerting capacity, so that non-flammable gas mixtures are considered flammable.
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- "Hauptsächlich handelt es sich hierbei um die Freisetzung von nicht brennbaren Gasen wie CO 2 (z.B. aus Calciumcarbonat) oder NH 3 (z.B. aus Melaminpolyphosphat ).  "
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ABSTRACT: Knowledge of material safety properties is critical for safe handing in the chemical process industries, especially for flammable chemicals that might result in serious fires and explosions. This study investigated the flammability characteristics of methanol under working conditions during the process. The targeted fire and explosion properties, like explosion limits (UEL and LEL), vapor deflagration index (K g), maximum explosion pressure (P max), and maximum explosion pressure rise [(dP dt −1)max], were deliberately obtained via a 20-L-Apparatus in 101kPa (i.e., 760mmHg/1atm), 150 and 200°C, along with various experimental arrangements containing nitrogen (N2) or carbon dioxide (CO2) as inert component. Particularly, this study discussed and elucidated the inert influence on the above safety-related parameters by two different inerting gases of N2 and CO2. The results indicated that adding an inert component to fuel–inert gas mixtures determined the decrease of explosion range and flammability hazard degree. The results also demonstrated that CO2 possessed higher inerting capability than N2 in this study.Journal of Thermal Analysis and Calorimetry 06/2009; 96(3):759-763. DOI:10.1007/s10973-009-0028-1 · 2.21 Impact Factor
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ABSTRACT: The inhibiting effect of Al(OH)3 and Mg(OH)2 dust on explosion of methane-air mixtures was investigated by means of explosion parameter tests in a 20-liter closed vessel. The influences of varying methane concentration and dust concentration on explosion parameters were characterized based on the experimental data to determine the maximum explosion pressure, maximum rate of pressure rise, lower explosion limits and upper explosion limits. The inhibiting mechanisms of these kinds of dust were analyzed as well. The investigations indicate that Al(OH)3 and Mg(OH)2 dust can be used as inhibitors to prevent methane explosion, however, their inhibiting effects are less than those of inert gas such as N2 and CO2 in that their dust can weaken the methane explosion but cannot totally eliminate it. The tests show that all of the explosion parameters with dust additives are strongly dependent on methane/air ratio and dust concentration, and Al(OH)3 dust has better performance than Mg(OH)2 dust in inhibiting methane explosion. The average percentage decreases of maximum explosion pressure and maximum rate of pressure rise with Al(OH)3 dust are 11.08% and 66.15%, respectively. Experiments also showed that there is a special phenomenon when methane explosion is inhibited by Al(OH)3 and Mg(OH)2 dust, in which is that during the process of explosion the maximum explosion pressure value first decreases then increases as dust concentration increases. The best dust concentrations to inhibit the explosion are 250 g/m3 with methane/air ratio at 9.5%, and 200 g/m3 with methane/air ratio at 7%. It is suggested that water vapor produced by the thermal decomposition of metal hydroxides makes the particles of descending dust combine, resulting in a decrease of the real dust concentration in the vessel. Water vapor also is the major cause of another phenomenon that the LEL curve and the UEL curve never meet with the increase of gas concentration.Science China Technological Sciences 05/2012; 55(5). DOI:10.1007/s11431-012-4771-3 · 1.11 Impact Factor