FLAMMABILITY LIMITS IN FLOWING ETHENE-AIR-NITROGEN MIXTURES: AN EXPERIMENTAL STUDY

Abstract- A large pilot plant was constructed to study the upper flammability limit of ethene-air-nitrogen mixtures under conditions offlow. The gas mixtures flowed through an explosion tube with a length of 3.0 m and a diameter of21 ram. An electrically heated wire was used as ignition source. Experiments were performed at pressures of 5 and 10 bar, with gas temperatures b tween 25 and 300 °C and with the wire fixed horizontally and vertically. Three different phenomena are observed: negligible r action, local reaction, and explosion. The negligible r action region occurs at power supply rates to the wire below aetitical value. Above this critical value ither alocal reaction or an explosion occurs. The critical oxygen concentration which separates the local reaction and explosion regimes depends on the experimental conditions: gas composition, pressure, t mperature, wire size and orientation, and gas velocity. An increase inpressure increases the upper flammability limit. Also an increase intemperature causes an increase inthe upper flammability limit and the results can be explained by assuming a constant flame temperature. Moreover, the upper flammability limit is influenced bythe gas velocity. Under conditions offlow the explosion region becomes smaller, itshifts to higher oxygen concentrations. I practise this may mean that partial oxidaion reactions can safely be operated at higher oxygen concentrations, provided gas flow rates are kept high