Measurement of flammability in a closed cylindrical vessel with thermal criteria

Abstract

Accurate flammability limit information is necessary for safe handling of gas and\nliquid mixtures, and safe operation of processes using such mixtures. The flammability\nlimit is the maximum or minimum fuel concentration at which a gas mixture is\nflammable in a given atmosphere. Because combustion occurs in the vapor phase, even\nin the case of liquids the flammability limits are applicable after calculating the vapor\ncompositions. The body of flammability data available in the literature is often\ninadequate for use with the variety of conditions encountered in industrial applications.\nThis is due to the scarcity of flammability data for fuel mixtures in non-standard\natmospheric conditions, and inconsistencies in flammability values provided by different\nexperimental methods.\nThis work reports on the design, construction and utilization of an apparatus\ncapable of measuring flammability limits for a range of conditions including fuel\nmixtures, varying oxygen concentrations, and extended pressure and temperature ranges.\nThe flammability apparatus is a closed cylindrical reaction vessel with visual, pressure\nand thermal sensors. A thermal criterion was developed for use with the apparatus based\non observations of combustion behavior within the reaction vessel. This criterion provides more detailed information about the combustion than is provided by the\npressure criterion methods.\nMeasured flammability limits of several hydrocarbon mixtures in air compare\nwell with limits obtained by open glass cylinder experiments, but not with the results of\ncounterflow apparatus experiments. The current results show that Le Chatelier’s rule\ndescribes the mixture results adequately. Minimum oxygen concentrations also were\ndetermined for methane, butane, and methane-butane mixtures and compared with\nvalues reported in the literature. Lower flammability limits were determined for an\nequimolar methane-butane mixture at varying oxygen concentrations.\nResults show that the flammability data determined with thermal criteria has an\nacceptable level of accuracy. Recommendations for improving apparatus are made,\nbased upon observations made while operating the flammability apparatus.