Spectral-kinetic Characteristics Glow of Fat Coal at Different Stages of Laser Ignition

The spectral-kinetic characteristics of hard coal were measured at various ignition stages by a pulsed YAG:Nd3+-laser ( $\lambda=1064\ \text{nm},\ \tau_{\mathrm{i}}=120\ \mu\mathrm{s}$ ). Three stages of ignition were established. At an energy density of $H=0.8\ \mathrm{J}/\text{cm}^{2}$ during the laser pulse, micro-protrusions ignite and the coal particles surface heats up to $T=3500\ \mathrm{K}$ . At an energy density of $\mathrm{H}=1.8\ \mathrm{J}/\text{cm}^{2}$ the evolvement and ignition of volatile matters take place. In the flame spectrum, at the initial instant of time, there is a glow of excited H2 molecules and CO flame. After the evolvement of volatile matters, the glow has a thermal spectrum associated with carbon particles emitted from the sample at a temperature $T=2500\ \mathrm{K}$ . At an energy density of $H=8\ \mathrm{J}/\text{cm}^{2}$ ignition of the non-volatile residue is observed, the flame spectrum is thermal with a temperature $T=1800\ \mathrm{K}$ .