Comparative study of the explosion pressure characteristics of micro- and nano-sized coal dust and methane-coal dust mixtures in a pipe

Coal dust explosion accidents often cause substantial property damage and casualties and frequently involve nano-sized coal dust. In order to study the impact of nano-sized coal on coal dust and methane-coal dust explosions, a pipe test apparatus was used to analyze the explosion pressure characteristics of five types of micro-nano particle dusts (800 nm, 1200 nm, 45 mu m, 60 mu m, and 75 mu m) at five concentrations (100 g/m(3), 250 g/m(3), 500 g/m(3), 750 g/m(3), and 1000 g/m(3)). The explosion pressure characteristics were closely related to the coal dust particle size and concentration. The maximum explosion pressure, maximum rate of pressure rise, and deflagration index for nano-sized coal dust were larger than for its micro-sized counterpart, indicating that a nano-sized coal dust explosion is more dangerous. The highest deflagration index K-st for coal dust was 13.97 MPa/(m.s), indicating weak explosibility. When 7% methane was added to the air, the maximum deflagration index K-st for methane-coal dust was 42.62 MPa/(m.s), indicating very strong explosibility. This indicates that adding methane to the coal dust mixture substantially increased the hazard grade.