โ Scribed by J.W. Bolk; N.B. Siccama; K.R. Westerterp
No coin nor oath required. For personal study only.
A large pilot plant was constructed to study the upper flammability limit of ethene-air-nitrogen mixtures under conditions of flow. The gas mixtures flowed through an explosion tube with a length of 3.0 m and a diameter of 21 ram. An electrically heated wire was used as ignition source. Experiments were performed at pressures of 5 and 10 bar, with gas temperatures between 25 and 300 ยฐC and with the wire fixed horizontally and vertically. Three different phenomena are observed: negligible reaction, local reaction, and explosion. The negligible reaction region occurs at power supply rates to the wire below a etitical value. Above this critical value either a local 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, temperature, wire size and orientation, and gas velocity. An increase in pressure increases the upper flammability limit. Also an increase in temperature causes an increase in the upper flammability limit and the results can be explained by assuming a constant flame temperature. Moreover, the upper flammability limit is influenced by the gas velocity. Under conditions of flow the explosion region becomes smaller, it shifts to higher oxygen concentrations. In practise this may mean that partial oxidaion reactions can safely be operated at higher oxygen concentrations, provided gas flow rates are kept high.
๐ SIMILAR VOLUMES
The limits o/]lammability o/ ethylene in oxygen, air and air-nitrogen mixtures were me~sured at elevated temperatures and pressures in a three litre spherical bomb. The limits in oxygen were determined at 80ยฐC, 120"C and 150ยฐC and over the range 135 to 515 lb /in"-abs. pressure. The limits in air a