Home – Home – Jornals – Chemistry for Sustainable Development 2019 number 6

Laser ignition (λ = 1064 nm, τ_i = 120 ms) of the coal samples of different marks from the Kuznetsk coal basin was studied. Three consecutive stages of ignition were detected for all marks of coal. These stages are characterized by the threshold radiation energy densities H_cr⁽¹⁾, H_cr⁽²⁾, H_cr⁽³⁾ which are characteristic for each coal marks. It was established that the first stage involves surface heating and ignition of micro protrusions on coal particles. The duration of this stage does not exceed the time of the laser pulse. At the second stage, volatile matter are observed to evolve and ignite. The duration of combustion depends on the density of radiation energy. Ignition of the nonvolatile residue occurs at the third stage, upon reaching H_cr⁽³⁾; burning time is 40-150 ms. It was demonstrated that the threshold value at the first stage varies only slightly for all coal marks. For bituminous coal, the second threshold decreases with an increase in coalification degree, while the third threshold increases. The second and the third thresholds for lignite are comparable with the values of H_cr⁽²⁾ and H_cr⁽³⁾ for low metamorphic bituminous coals. Experimental results allow us to conclude that ignition occurs at the first and the third stages according to the heterogeneous mechanism, while at the second stage it occurs according to a homogeneous mechanism.