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The knowledge of the explosion limits of biogases in air is necessary to define explosion protection measures. Biogases from agricultural plants vary however in their composition, so that for each gas composition the explosion limits would have to be measured. Frequently the explosion limits of biogas are therefore referred in the safety-relevant literature only to the methane fraction of the gas mixture, without indicating this additionally. This leads to the fact that the explosion ranges for the total mixture consists of methane, carbon dioxide and further residual gases are falsely specified.
For this reason a simple method is presented in the following, which show, how the explosion limits of a biogas can be determined from its methane content using an explosion diagram of methane/carbon dioxide/air system. The explosion diagram was measured according to the German Standard DIN 51649-1.
The presented calculation method supplies however correct results only if the nitrogen fraction in the biogas does not exceed approx. 5 % by volume.
An important method to prevent fires and explosions is to avoid explosive fuel-air mixtures. For this purpose the exact knowledge of the explosion range is required as a function of the combustible, oxidizer and inert gas concentrations. Frequently triangular diagrams are used in order to display the explosion range of such three component gas mixtures. Beside the explosion limits and the explosion range other characteristics can be deduced from explosion diagrams. More than 200 of such explosion diagrams are available in the database CHEMSAFE®, included among others. The in-house version of the database is able to provide all characteristics of a chosen system by means of a TRIANGLE-software. Furthermore a recently published German data book contains 158 explosion diagrams. Many diagrams were measured according to the German DIN 51649 standard. Other systems are available for elevated initial pressures and temperatures. This paper describes how to use the TRIANGLE software for flammability diagrams and the meaning and use of derived characteristics (MOC, MXC, MAI) for explosion prevention. Furthermore a calculation method for the flammability of gas mixtures is shown using the MXC values.
An important method to prevent fires and explosions is to avoid explosive fuel-air mixtures. For this purpose the exact knowledge of the explosion range is required as a function of the combustible, oxidizer and inert gas concentrations. Frequently triangular diagrams are used in order to display the explosion range. This paper describes how to use the TRIANGLE software for flammability diagrams. Furthermore a calculation method for the flammability of gas mixtures is shown.