Energy Sources, vol.23, no.4, pp.337-344, 2001 (SCI-Expanded)
Mengen lignite was pyrolyzed in a thermobalance apparatus at atmospheric pressure. The effects of heating rate and particle size on the pyrolysis kinetics were investigated. Experiments were conducted at nonisothermal conditions with a heating rate range of 10-90 K/min in the pyrolysis temperature interval of 298-1173 K under an argon atmosphere. Two particle size ranges were examined: 125 > Dp > 63 and 63 > Dp > 44 μm. Although some differences were obtained in TG/DTG curves of the lignite samples at different heating rates, almost constant relative yields of 45 and 40% of the total volatile matter were calculated from 673 to 873 K for the linear segments of the TG curves of the larger and smaller size particles, respectively. Thermogravimetric data were analyzed by a reaction rate model assuming first-order kinetics, and kinetic parameters were determined. Lower activation energies were calculated at higher heating rates. Minimum activation energy was obtained as 22.4 kJ/mol at the heating rate value of 90 K/min with 63 > Dp > 44 μm size lignite particles. It appears to be the lowest one when compared to those obtained from the literature. Copyright © 2001 Taylor & Francis.