(35g) Pyrolysis Kinetics of Live and Dead Wildland Vegetation from the Southern United States

Amini, E., Brigham Young University
Safdari, M. S., Chemical Engineering Department, Brigham Young University, Provo, UT 84602, USA
Fletcher, T., Brigham Young University
Weise, D. R., USDA Forest Service

The fundamental combustion behavior of live wildland vegetation is not fully understood. Since the combustion process during prescribed burning starts with pyrolysis, there is a need for better understanding of pyrolysis. The kinetics of pyrolysis of live and dead wildland vegetation has not been explored in detail. In this study, the pyrolysis kinetics were determined for 14 different plant species (live and dead) which are all native to the forests in the southern United States. Pyrolysis experiments were carried out in a Thermogravimetric analyzer (TGA) under inert conditions, and operated at 5 different heating rates ranged from 10 to 30 ℃ min-1. The iso-conversional and model free methods of Starink, KAS, and Kissinger were used to calculate the activation energies and pre-exponential factors. Furthermore, the dependence of activation energy on conversion fraction, type of plant species, and plant condition (live and dead) was investigated. For some plant species such as live little bluestem grass, an increase in activation energy with conversion was observed in the major pyrolysis zone. Live and dead samples from the same plant species were found to have different activation energies. In addition, the simple one step reaction model and distributed activation energy model (DAEM) were used to find kinetic parameters. All models were compared with the data to determine the best model to describe the pyrolysis behavior of these plant species.

Keywords: Pyrolysis, Live plant, Biomass, Kinetics, TGA