Explosion characteristics of H2/CH4/air and CH4/coal dust/air mixtures

Using a standard 20 L explosion spherical vessel, the explosion characteristics of H2/CH4/air and CH4/coal dust/air mixtures as well as the solid explosion products were investigated. Results show that the presence of molecular hydrogen yield from coal spontaneous heated process would significantly increase the maximum explosion pressure and pressure rise rate of H2/CH4/air mixtures. With the increasing of hydrogen contents in the mixtures, the lower explosion limits decrease correspondingly. In the cases with appropriate hydrogen and methane ratio, the lower explosion limits of the mixture are even smaller than that of each gas componentsʹ. The rules of CH4/air/coal dust hybrid mixtures explosion parameters present a increasing and then decreasing trend with the methane contents in the hybrid mixtures, and the peak values appear at the point that the methane volume fractions is 0.1. Furthermore, dust explosion processes and some influencing factors, such as dust concentration and initial pressure and so on, are also analyzed and discussed systematically. Supported with the scanning electron microscope (SEM) and image processing technology, the surface fractal characteristics of solid explosion products are analyzed and compared for each coal dusts. Research results may have great significance for the hybrid mixtures explosion kinetic reveal, risk assessment and preventions in the coal mine.