Experimental investigation of moisture content on suppressing ignition of accumulated dust

The moisture content sprayed into the dust layer in industrial sites was one of the main factors affecting the occurrence of reignition, which could prevent fire and explosion accidents. Although moisture was traditionally considered to inhibit ignition by endothermic and delayed drying, its effect on the thermophysical properties of the dust layer cannot be ignored due to a certain degree of influence on the heat transfer and heat absorption processes of the dust layer. In present study, six wheat straw samples with MCs from <0.2% to 50% MCs were tested with the hot plate methods, and the heat and mass transfer at four stages during the smouldering processes were discussed. The effect of MC on the ignition time, critical ignition temperature, and mass-loss characteristic parameters of the samples was determined. As MCs increased, the thermal conductivity of the sample increased from 0.110 to 0.248 W/(m·K), as well as the heat sink density (ΔHs) increased from 6.66 × 105 to 16.28 × 105 J/kg. It was necessary to make ΔHs higher than the heat increase value (ΔQ) for suppressing ignition.