Experimental study of tobacco dust smoldering on superheated surface
ZHANG Xiangliang;HE Rui;CAO Xinguang;SONG Huijuan;College of Urban Construction and Safety Engineering,Shanghai Institute of Technology;
To study the influencing factors on the occurrence of burning, the cone calorimeter was used to test the determination of dust's heat release rate and improve the existing test device for ignition temperature of dust layer, 3 groups of the tobacco dusts in different particle sizes smoldering on the surface of the heat were studied through experiments. The result shows that the heat release rate peaks of sliced tobacco dust, picadura dust and rolled tobacco powder are 90, 91 and 75 k W/m~2 respectively and the flame propagation speed of the picadura dust is the fastest. The rolled tobacco powder whose peak is the lowest begins to smoke around50 s, taking the lead among these three tobacco dusts in heat release, then the picadura dust and sliced tobacco dust release the heat at 75 s and 80 s respectively. The smoldering process can be analyzed in stages,in the stage of water evaporation and fuel oxidation, the dusts' temperature rise stably, and the temperature jumps in the stage of exothermic oxidation. Thus, to control the smoldering, we must take measures and make the corresponding effective early warning scheme to control the trend of its development before the stage of water evaporation and fuel oxidation; The first occurrence of dust smoldering is on the top layer, then the smoldering spread down until the dust completely burnt out, when the dust layer reached the smoldering temperature, the top layer's heating rate is the highest, when the middle and bottom layers are not smoldering, the top layer preheats them. The smoldering time and duration of experiment are increased with the increase of particle size, each stage's smoldering duration decreases with the decreasing of particle size which make the dust smolder faster and harder to control.