Accurate flammability limit information is necessary for safe handling of gas and liquid mixtures, and safe operation of processes using such mixtures. The flammability limit is the maximum or minimum fuel concentration at which a gas mixture is flammable in a given atmosphere. Because combustion occurs in the vapor phase, even in the case of liquids the flammability limits are applicable after calculating the vapor compositions. The body of flammability data available in the literature is often inadequate for use with the variety of conditions encountered in industrial applications. This is due to the scarcity of flammability data for fuel mixtures in non-standard atmospheric conditions, and inconsistencies in flammability values provided by different experimental methods. This work reports on the design, construction and utilization of an apparatus capable of measuring flammability limits for a range of conditions including fuel mixtures, varying oxygen concentrations, and extended pressure and temperature ranges. The flammability apparatus is a closed cylindrical reaction vessel with visual, pressure and thermal sensors. A thermal criterion was developed for use with the apparatus based on observations of combustion behavior within the reaction vessel. This criterion provides more detailed information about the combustion than is provided by the pressure criterion methods. Measured flammability limits of several hydrocarbon mixtures in air compare well with limits obtained by open glass cylinder experiments, but not with the results of counterflow apparatus experiments. The current results show that Le ChatelierAcA?A?s rule describes the mixture results adequately. Minimum oxygen concentrations also were determined for methane, butane, and methane-butane mixtures and compared with values reported in the literature. Lower flammability limits were determined for an equimolar methane-butane mixture at varying oxygen concentrations. Results show that the flammability data determined with thermal criteria has an acceptable level of accuracy. Recommendations for improving apparatus are made, based upon observations made while operating the flammability apparatus.
