variavel0=<b>R. Pilão</b> - rosap@inegi.up.pt CIEA-ISEP
<b>E. Ramalho</b> - elisa@dec.isep.ipp.pt CIEA-ISEP
<b>C. Pinho</b> - ctp@fe.up.pt UNIV. PORTO
<b>Abstract.</b> Flammability studies of air cork dust mixtures were conducted in the 20 L US Bureau of Mines explosibility test chamber, using 2500 J pyrotechnic ignitors. The dust burned as air-dispersed dust clouds and the uniformity of the particles dispersion in the chamber was detected through optical probes. The range of tested particle sizes went from 45 to 350 mm, whereas the dust cloud concentration was up to 600-700 g/m3. Measured explosions parameters included minimum explosible concentration, maximum explosion pressures and maximum rate of pressure rise. The effect of dust particle size on flammability was evaluated and was found that minimum explosible concentrations were relatively independent of particle size below 180 mm. Highest explosion pressure and rate of pressure rise, were detected at the finest tested sizes. The measured flammability limits for this heterogeneous system are shown to be consistent with the established mechanisms and processes for homogeneous flame propagation, provided that the heating and devolatilization of the solid fuel is also considered. The limitations on the rates of devolatilization of the solid particles became rate controlling at high burning velocities, at high dust loadings and for large particle sizes.
<b>Keywords.</b> dust explosions, air and cork dust, explosibility.