Ignition of Coal Microparticles in an Air Atmosphere and Their Influence on the Inflammation of Methane

The spontaneous combustion of the coal microparticles of fractions 1–20 μm and 20–32 μm in an air atmosphere and the inflammation of the coal microparticles of fraction 20–32 μm in a methane–air mixture at temperatures of 700–1100 K were investigated with the use of a rapid compression machine. A contactless measurement of the temperature of the coal particles ignited spontaneously in a gas has shown that this temperature can reach 2500 ± 200 K and substantially exceeds the temperature of the gas at the end of its compression stroke. It was established that the coal microparticles burning in a stoichiometric methane–air mixture are local hotbeds of fire in this mixture at a temperature as high as 1400 K and that the gas is ignited in the neighborhood of these hotbeds. The limiting temperatures of ignition of the coal microparticles in an air atmosphere free of methane and in a methane–air mixture were determined. The measured times of delay in the ignition of the methane by the coal microparticles in a hybrid methane–air mixture agree with the delay times of ignition of a pure methane–air mixture under the same conditions to within the experimental error.