Pirólise de bagaço de malte e resíduo de erva-mate: caracterização e estudo cinético por métodos isoconversionais

Abstract

Biomass is considered a viable alternative for diversifying the energy matrix, and its use as fuel is due to numerous advantages as low Sulphur content and the neutrality related to the CO2 emissions. The production of biofuels can be made by the pyrolysis of biomass, being essential the analysis of the reaction kinetics in order to elucidate the involved mechanisms for a large range of operating conditions. In this work, it was carried out the pyrolysis kinetic study of two agroindustrial residues, the malt bagasse (MB) and the yerba mate residue (YMR), by thermogravimetry. Tests were performed with four heating rates (10, 15, 25 and 40°C min-1), up to the final temperature of 900 °C. From the thermogravimetric data, it was possible to calculate the activation energy (Ea) for each conversion using the isoconversional methods of Flynn-Wall-Ozawa (FWO), Kissinger-Akahira-Sunose (KAS) and Friedman. The values found for Ea were between 161.25-276.80 kJ mol-1 for MB and 142.36-275.21 kJ mol-1 for YMR. Regarding the biomass characterization, it was possible to verify, from the proximate analysis, that both residues present similar volatile matter contents, of 80.5%. The theoretical high heating value (HHV) was higher for the MB, being 19.60 MJ kg-1. From the scanning electron microscopy (SEM) analysis, it was observed the particle size (less than 300 μm) and its fibrous morphology; being the MB more homogeneous and porous. Finally, the biomasses ashes were analyzed by X-ray fluorescence spectrometry (XRF), being found as major oxides the silicon for MB and potassium for YMR.