Potencial de aproveitamento da casca de pinhão (Araucaria angustifolia) no processo de pirólise em termos de suas propriedades físico-químicas e parâmetros cinéticos

Abstract

The high energy demand, the reduction of fossil fuels and the acceleration of the greenhouse effect are factors that have been contributing to the search for renewable energy sources. Biomass has stood out for being a source of clean energy and of low emission of polluting gases into the atmosphere. Through the pyrolytic conversion process, biomass is valued and generates products both in liquid, as in gaseous and solid state. In this context, this work aimed to evaluate the energetic potential of pinion shell (CP) through its physicochemical characterization and the kinetic study of pyrolysis by thermogravimetry (TG). The experiments were carried out for a CP mass of 10 mg, in an inert N2 atmosphere, with a controlled flow of 100 mL min-1, at four heating rates (10, 15, 25 and 40°C min-1), from room temperature up to 900°C. From the TG data, the kinetic parameters of activation energy (Ea) were estimated by the Flynn-Wall-Osawa (FWO), Kissiger-Akira-Sunose (KAS) and Starink (STK) isoconversional models, and the pre-exponential factor (A) was found by the Kissinger method. The studied CP residue had a high content of volatile matter (71,98%), a low ash content (1,28%) and low amounts of sulfur (0,12%) and nitrogen (0,69%). Its superior calorific value (PCS) was calculated by different theoretical correlations and resulted in an average value of 20.68±1.08 MJ kg-1, demonstrating its fuel potential. The morphology of the sample exhibited heterogeneity and low porosity. From the TG data and its derivative (DTG), it was possible to determine the mass losses and the degradation temperatures of the different biomass components (hemicellulose, cellulose and lignin) during the pyrolysis process. The value of Ea of the pyrolysis of the pine shell ranged between 170.3 and 260.4 kJ mol−1 for the FWO method, between 160.8 and 255.3 kJ mol−1 for the KAS method, and between 161.5 and 256.0 kJ mol−1 for the STK method, in the conversion range of 0.05 < α < 0.90. The mean pre-exponential factor of pine shell pyrolysis estimated was 3.30×1017 min−1. Overall, the results highlighted the potential use of pinion shell for bioenergy production and provide a basis for the reliable design of pyrolysis reactors using this food residue as a renewable solid fuel.