Laser Pyrolysis of Lignite with Different Mineral Compositions

The pyrolysis of lignite microparticles (0.5–63.0 μm) in tablet form (ρ = 1 g/cm3) under the action of pulsed periodic laser radiation (1064 nm, 14 ns, 6 Hz, 0.2–0.5 J/cm2) is studied, for samples with different ash content (A = 10.1 and 0.5%). The laser pulses produce ablation of the samples: coal particles (10–50 μm) are emitted, and carbon atoms evaporate from the surface. Laser radiation absorbed in the surface layer triggers thermochemical reactions that develop by a chain mechanism. The gaseous products H2, CH4, C2H2, CO, and CO2 are produced in both types of samples. The yield and generation rate of the synthesis gas (H2 and CO) increase with ash content of the samples. This indicates that mineral impurities have a catalytic effect on the gasification of lignite in laser pyrolysis.