Kinetic parameters and heat of reaction for forest fuels based on genetic algorithm optimization

Abstract

Environmental issues and climate change are playing a central role in our society. Forest and peatland fires can prejudice the environment and population health. Therefore, it is vital to study this phenomenon. The main goal of this work is to determine the kinetic parameters and heat of reaction for different forest fuels. Pine needles and sphagnum peat are typical fuels from the Northern Hemisphere, while Amazonian leaves and high-density peat are from the Southern Hemisphere. The DTG curves for pine needles and Amazonian leaves clearly show two peaks of mass loss, while for sphagnum peat a third mass-loss peak occurs for higher temperatures. For high-density peat degradation, there is only one significant peak of mass loss, which happens at a higher temperature. Also, the DSC curves for pine needles, Amazonian leaves, and high-density peat show two exothermic peaks along with the mass-loss peaks. However, the overall pattern is not the same. The maximum heat released for pine needles and high-density peat occurs at the second degradation stage. There are two exothermic peaks of almost the same magnitude for Amazonian leaves. Finally, three exothermic peaks match the peaks of mass loss for sphagnum peat. DTG and DSC curves patterns for all forest fuels are independent of the heating rate and atmospheric composition. In this work, the proposed pseudo reaction mechanism for pyrolysis and oxidation of the forest fuels contains five (for Amazonian leaves, high-density peat, and sphagnum peat) and seven (for pine needle) steps. The genetic algorithm optimization process compares the instantaneous recorded data of TGA, DTG, and DSC with the calculated ones. The optimized kinetic reactions parameters for the forest fuels are the activation energy, the pre-exponential factor, the global order of reaction, the stoichiometric coefficients, and the heat of reaction. The overall performance of the proposed mechanism is evaluated taking the error or the experimental data into account. This set of reaction kinetics parameters allows for a suitable numerical model for forest fires. To the authors' knowledge, a comprehensive assessment of the above parameters, including the heat of reaction, for forest fuels is lacking.