Abstract:

To support fire risk assessment and fire prevention management in ancient cypress forests, the bark, leaves, and branches of ancient cypress were selected as the research objects. Proximate analysis and thermal analysis tests in air were conducted to investigate the compositional characteristics, mass-loss processes, heat-release behaviors, and effects of heating rate on the pyrolysis of different combustible materials. Iso-conversional methods were employed to analyze the kinetic characteristics in the main pyrolysis reaction region. The average apparent activation energy, total heat release, and peak heat flux were selected as evaluation indicators, and the entropy weight method was used to determine the fire hazard of different combustible materials. The results show that the bark, leaves, and branches all exhibit three characteristic stages of dehydration, rapid mass loss, and burnout. The main mass-loss region is 200-500 ℃, and the major exothermic peaks are concentrated at 300-460 ℃. Heat release is mainly attributed to the oxidation of volatile products and residual char in air. The bark has an ash content of 21.78% and a pyrolysis residue yield of 18%-24%, indicating that its pyrolysis progression is hindered. The leaves have the lowest average apparent activation energy (164.03 kJ/mol), indicating that pyrolysis occurs more readily. The branches exhibit a total heat release of 5 796.33 J/g and show a stronger capacity for sustained heat supply. The fire hazard is ranked as branches > leaves > bark.

Key words: ancient cypress, combustibles, pyrolysis characteristics, fire hazard, apparent activation energy, composite index