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.