Estudo da decomposição térmica do biocarvão de macaúba

Abstract

The kinetics of the thermal decomposition of solids involves the determination o important calorimetric parameters for the knowledge of promising materials for sustainable energy generation. This study is done traditionaly through Termogravimetric Analysis, with which is possible to obtain detailed informations about the decomposition reaction. With these, we can utilize traditional methodologies, like the Vyazovkin method, or inovative ones, for instance an artificial neural network, in order to gather kinetic descriptive paramethers of the reactions. Taking into account the current global energetic panorama, the development of new energetic sources, that are sustainable and renewable, is essential. Therefore, in this work, different samples of biochar were studied. These were by-products of the thermal liquefation of different parts of the Macaúba fruit, which are: the endocarp, the kernel cake, and the pulp cake, and those were also done in different solvents. Thus, in order to study the kinetic decomposition and thermal behaviour of the biochars, dinamic thermogravimetric analysis were made, employing three different heating rates. It was observed that the biochars made from the kernel cake are thermically more stable, with lower medium velocity of decomposition and values of activation energy varying from 88 to 119 kJ mol-¹. On the other hand, the endocarp biochars showed an activation energy varying from 86 to 108 kJ mol-¹, and, subtracting this value from the total energy released from its combustion, presented a higher final energetic balance. The traditional kinetic models fit of the graphical curves of conversion degree and temperature had a high error value. The main model that fitted best the experimental data of the biochars was the F2 model. Finally, the neural network fit got more assertive outcomes, with lower error, and showed that the Avrami-Erofeyev models have higher contribution for the description of the event. This result confirms that the decomposition event of the biochars does have a complex reactional mechanism.