A study on the ignition characteristics for dust explosion of industrial wastes

Paying attention to accidents related to recycling, the authors investigated factors related to the dust explosions. The minimum explosive concentrations were 30-40 g/m3 (polyurethane and plastic dusts) and 70 g/m3 (toner); the explosibility was reduced by about 40% when combustible gas (cyclopentane) existed together with the dust; ignition temperature of a dust cloud was around 500 °C; and the minimum ignition energy was about 11 mJ (polyurethane). Ignition energy was the minimum when the spark duration was about 0.2 ms or more; the explosion probability was the maximum when the spark gap was 5-10 mm; and the ignition energy was the minimum when the electrode tip angle was around 30 °C (polyurethane). From these findings, the dusts produced in the recycling process can be easily evaluated so as to know whether dust explosion is likely to occur.