The study presents a comparative investigation of the yield of gaseous products released during the pyrolysis of a tableted sample of lignite microparticles under the influence of pulsed-periodic laser radiation (6 Hz, 1064 nm, 0.2-2 J/cm2) with nanosecond (12 ns) and microsecond (120 ms) pulse durations. The laser pyrolysis of the coal samples was conducted in an argon atmosphere, with the gaseous products analysed using mass spectrometry. The gaseous pyrolysis products under microsecond pulses contained H2, CH4, H2O, CO, and CO2, while under nanosecond pulses, H2, CH4, C2H2, CO, and CO2 were detected. The yield of gaseous products and the proportion of combustible gases per unit laser pulse energy density were higher for nanosecond laser irradiation. The mass of ablation products from the tableted coal microparticle sample under nanosecond pulses of the same energy density was greater than under microsecond pulses. The observed results are attributed to optical breakdown induced by high-intensity nanosecond pulses, leading to the increased formation of gaseous products and the generation of a stronger shock wave, causing ejection of particles from the tableted sample volume and rapid sample destruction.
Aduev et al. (Tue,) studied this question.