Pyrolysis and combustion characteristics and kinetics of wood sawdust and wood sawdust hydrochar

This study compares the pyrolysis and combustion characteristics with the kinetics of wood sawdust and its hydrochar. Wood sawdust hydrochar was obtained by the hydrothermal treatment of wood sawdust (biomass/water: 1 g/4 mL) at 220°C, where the residence time was set as 90 min. After hydrothermal carbonization, carbon content and heating value were both increased by 14%. Pyrolysis and combustion of wood sawdust and its hydrochar were performed by thermogravimetric analysis at 10, 20, 30, and 40°C/min. Kissinger–Akahira–Sunose (KAS) method, Friedman method, Flynn–Wall–Ozawa (FWO) method, and Kissinger method were used for analyzing the pyrolysis data. For combustion, only KAS and FWO methods were used to determine the kinetic parameters. As compared to wood sawdust pyrolysis, average activation energy of hydrochar pyrolysis was lower (150.36 kJ/mol by using KAS method, 153.05 kJ/mol by using FWO method). Based on mean activation energies, pyrolysis reaction of hydrochar was more favorable than its combustion. In combustion, average activation energy of hydrochar combustion reaction was higher; indicating that combustion of wood sawdust was more favorable.