A study on the ignition of different metamorphic grade coal particles by microsecond laser pulses in the free-running mode

The ignition of different metamorphic grade coal particles by microsecond laser pulses (laser wavelength 1064 nm, pulse duration 120 mu s, maximum energy per pulse 1.3 J) was studied. Three stages with characteristic ignition thresholds and durations of combustion were revealed. The fraction of the laser pulse energy absorbed by flame and thermal decomposition products of coal particles was determined; reflection and absorption coefficients of coal particles were measured at each ignition stage. Ignition thresholds of coal particles were established taking into account the fraction of laser pulse energy absorbed by flame and thermal decomposition products, and the reflection coefficient. At the first stage, reactive microprotrusions ignite on the surface of coal particles. A model was proposed to describe the processes occurring at the second and third stages of ignition.

Automated summary

This study investigated the ignition characteristics of coal particles with different metamorphic grades under microsecond laser pulses and revealed three stages with distinct ignition thresholds and combustion durations. The energy fraction absorbed by flame and thermal decomposition products of coal particles was determined, and the reflection and absorption coefficients of coal particles were measured at each ignition stage.