Ignition of Low-Metamorphized Coal with Continuous Lasers at Wavelengths 450 nm and 808 nm

The paper presents the results of a comparative investigation into the kinetic and energy characteristics of the ignition of microparticles of low-metamorphized coal ranks (lignite coal and high volatile C bituminous coal) under the impact of laser radiation at the wavelengths λ = 450 nm and λ = 808 nm with an exposure time of 1 sec. Coal ignition is carried out only during irradiation. There is no transition to stationary combustion. The ignition delay time decreases monotonically with increasing radiation power density. It is established that the energy costs of ignition of the studied coal ranks may be made more economical by using laser radiation with a wavelength of λ = 450 nm. It is concluded from the results of measuring the energy characteristics of coal ignition that the absorption of radiation has a quantum nature. Two components contribute to the coal particles emission spectra measured at the initial stage of ignition: CO (CO2*) flame and thermal glow associated with emitted carbon particles heated to T>2000 K for both coal ranks. At subsequent stages, only the glow of heated carbon particles with the thermal spectrum at T~2000 K is observed in the spectra.