Ignition of brown coal microparticles by the pulses of the second harmonic of nanosecond neodymium laser

Under the action of pulses of neodymium laser second harmonic (532 nm, 10 ns) on microparticles of brown coal in the form of the tablets with 1 g/cm³ density (particle size being less than 63 μm), two stages different in kinetic characteristics and threshold energy densities were distinguished.At the first stage, when the energy density reaches 0.4 J/cm², there occurs an optical breakdown and a plasma torch is formed immediately after the laser pulse with a lifetime of ∼1 μs. When the energy density reaches 4 J/cm², in addition to the processes of the first stage thermochemical reactions are initiated in the volume of coal microparticles, and volatile substances and non-volatile residue are released and ignited in the time interval of 30–500 μs.