Spectral-Kinetic Characteristics of Laser Ignition of Pulverized Brown Coal

In this study, we measured the spectral-kinetic characteristics of ignition of dustlike (pulverized) coal particles with a particle size of 100 m using an yttrium-aluminum garnet laser with an admixture of neodymium operating in the free-running mode (120 s). We discovered three stages of the process, each of which has a threshold character. During the laser pulse in the energy density range of 0.3-1.5 J/cm(2), a rapid heating of the sample surface to 3000 K occurs due to the absorption of laser energy and initiation of a chemical reaction in the coal particles. In the energy density range of 1.6-2.1 J/cm(2), the yield and ignition of volatile matter above the sample surface are observed in the time interval of 0.5-2 ms. In the emission spectra of the flame, we are able to distinguish bands associated with the combustion of volatile matter including the CO flame and the emission of excited H2O and H-2 molecules. At H > 2 J/cm(2), ignition and burning of the coke residue takes place in a time interval of 10-100 ms. Its emission spectrum corresponds to the emission spectrum of a black body at 1800 K.