Pyrolysis of the hybrid energy cane: thermal decomposition and kinetic modeling using non-isothermal thermogravimetric analysis

This work aims to investigate the thermal decomposition and reaction kinetics of the hybrid energy cane, as well as its thermochemical properties. Lower and higher heating values (15.42 and 17.01 MJ kg−1, respectively) as well as the cellulose content (45.61%, extractive-free basis) were similar to native energy canes and sugarcane residues. The thermogravimetric analysis was conducted using four heating rates (5–20 K min−1) in a nitrogen atmosphere. Three thermal decomposition stages were distinguished: dehydration, pyrolysis, and carbonization. Two mathematical approaches (single-step and multistep reaction models) were evaluated for pyrolysis. Considering the first case, activation energies (92.5–234.4 kJ mol−1) were calculated applying isoconversional methods (Friedman, Flynn–Wall–Ozawa, modified Coats–Redfern, and Vyazovkin), conversion function which represents the reaction model (sixth-order reaction) by the master plots method, and pre-exponential factor logarithm (11.40 s−1) by the linearization method considering the global activation energy (135.8 kJ mol−1). For the second case, average activation energies (63.0–174.0 kJ mol−1), pre-exponential factors logarithm (1.82–12.24 s−1), reaction orders (1–1.5), and compositions (0.20–0.32) were obtained in all heating rates for extractives, hemicellulose, cellulose, and lignin, applying independent parallel reactions scheme (IPRS). Simulating conversions and conversion rates for both approaches, the IPRS showed better agreement with experimental data (average deviation < 5%).