THERMOGRAVIMETRIC ANALYSIS OF THE PYROLYSIS OF Acacia mearnsii de Wild. HARVESTED IN RIO GRANDE DO SUL, BRAZIL

The present work aimed at investigating the effects of temperature, heating rate and time on the efficiency and kinetics parameters of the pyrolysis process of Acacia mearnsii De Wild. wood. The pyrolysis behavior was experimentally investigated through thermogravimetry (TGA). The kinetics parameters were obtained from dynamic and isothermal runs. Dynamic runs were performed from room temperature to 900 degrees C under heating rates ranging from 2 to 50 degrees C. min(-1). Isothermal experiments were carried out from 250 to 750 degrees C, by heating the sample to the desired temperature and keeping at that temperature for 2 hours. The dynamically obtained data were evaluated according to the Ozawa and Kissinger methods. On the other hand, the isothermally obtained ones were treated considering that the pyrolysis reaction follows a first order reaction over the entire range of time and temperature. The results evidenced the applicability of the methods since the activation energy for the pyrolysis process calculated from both methods resulted very similar, i.e., 170-180 kJ.mol(-1) from dynamic models and 140 kJ.mol(-1) from the isothermal method, as well as resulted very close to previously reported values for the activation energy of cellulose pyrolysis (150-200 kJ.mol(-1)). The results contribute to better understand biomass pyrolysis processes, in particular the A. mearnsii pyrolysis, leading to an improvement of the presently applied methods for charcoal biomass conversion.