Combustion reactivity of sewage sludge hydrochar derived from hydrothermal carbonization via thermogravimetric analysis

Wastewater treatment plant sludge contains a high concentration of organic compounds that can be used to produce fuel viahydrothermal carbonization (HTC). This study investigated the combustion reactivity and kinetic parameters of hydrochars produced to understand the combustion behavior of the solid fuel derived from HTC. The hydrochar was produced at various temperatures ranging from 150 to 300 degrees C, reaction times ranging from 30 to 150 min, and solid loadings ranging from 10% to 30%. The combustion behavior of sewage sludge (SS) and hydrochar was evaluated using thermogravimetric analysis with a constant air flow rate (100 mL/min) and heating rate (10 degrees C/min) from ambient temperature to 900 degrees C. It was observed that the HTC temperature, reaction time, and solid loading influenced the combustion characteristics and kinetics of the hydrochar. Additionally, the hydrochar exhibited higher ignition and burnout temperatures and a lower peak temperature than SS, indicating superior performance and reactivity in combustion. The combustion kinetic analysis also revealed that the hydrochar had a range of lower activation energy (29.12-41.60 kJ/mol) than SS (52.95 kJ/mol). Therefore, hydrochar derived from SS has the potential to be used as a substrate for solid fuel production for future renewable energy sources.