Home – Home – Jornals – Chemistry for Sustainable Development 2020 number 6

Laser ignition (1064 nm, 120 μs) of the dispersed particles of different coal marks was studied. For all coal marks, three consecutive ignition stages with characteristic threshold radiation energy densities ( H _cr) for each stage were discovered. With an increase in the rank, the values of the first ignition limit H _cr⁽¹⁾ remain almost constant, the second ignition limit H _cr⁽²⁾ decreases, while the third ignition limit H _cr⁽³⁾ increases. Results of the investigation of kinetic dependencies of flame glow at different ignition stages arising under the action of laser pulses on coal particles are presented. The glow duration at the first ignition stage slightly exceeds the duration of the laser pulse and reaches 150 μs for all marks of coal. The glow duration at the second ignition stage at H = H _cr⁽²⁾ is in the millisecond time interval. With an increase in the energy density of laser radiation, the glow duration at the second ignition stage decreases to the submillisecond range as a result of an increase in the rates of thermochemical reactions. At the third ignition stage at H = H _cr⁽³⁾, the glow duration is 10-100 ms for different marks of coal. It was established that for the studied coals, the glow intensity increases from the moment of exposure to laser pulse. In the submillisecond range, a decrease in glow intensity was observed. The glow amplitude of coals increases linearly with an increase in the energy density of laser radiation.