Pyrolysis of Coal by Nanosecond Laser Pulses

The action of nanosecond laser pulses (wavelength 532 nm, pulse length 14 ns, pulse repetition rate 6 Hz, energy density of laser radiation 0.2–0.6 J/cm²) in G and Zh coal pellets is investigated, in an argon atmosphere. The gaseous products of sample pyrolysis include H₂, CH₄, C₂H₂, CO, and CO₂. The content of the gaseous components is determined as a function of the laser energy density. In the range 0.2–0.4 J/cm², the volume of flammable gases formed (referred to the mass loss of the sample) increases; at higher energy densities, practically no change in volume is observed. The gross calorific value of the flammable gases increases linearly from ~8–10 to 19 MJ/m³ with increase in energy density of the laser radiation from 0.2 to 0.6 J/cm². A nanosecond pulse of energy density more than 0.4 J/cm² results in intense ablation of the pellets containing 0.005 wt % polyvinyl alcohol. The coal pellets that contain no binder break down under the action of a nanosecond laser pulse of energy density exceeding 0.2 J/cm².