This paper presents the results of experimental investigation on characteristics of methane-coal dust mixture explosion and its mitigation by ultra-fine water mist. Four E12-1-K type fast response thermocouples, two PCB piezotronic pressure transducers were used to obtain the temperature and pressure history of methane-coal dust mixture explosion and its mitigation by ultra-fine water mist, while a GigaView High-speed camera was used to visualize the processes. Different methane concentrations, coal dust concentrations, diameters of coal particles and volumes of ultra-fine water mist were considered for their effects on methane-coal dust mixture explosion. The temperature of explosion flame, the maximum explosion overpressure, the maximum rate of overpressure rise, and the critical volume flux of ultra-fine water mist were experimentally determined. The results show that the characteristics of the methane-coal dust mixture explosion and the mitigating efficiency by ultra-fine water mist are influenced by the methane concentration, the coal dust concentration, the coal dust diameter and the applied volume flux of ultra-fine water mist. For example, both the maximum explosion overpressure and rate of overpressure rise increased with increasing of coal dust concentrations and methane concentrations. All of the test cases indicate that ultra-fine water mist can mitigate the mixture explosion and suppress the flame propagation efficiently from the images record by high speed video camera.

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