Effects of Hydrothermal Carbonization Conditions on the Combustion and Kinetics of Wheat Straw Hydrochar Pellets and Efficiency Improvement Analyses

Hydrothermal carbonization conditions can affect the combustion and kinetics of wheat straw hydrochar pellets. Temperature and time are the key influencing factors of the hydrothermal carbonization reaction. Hence, exploring the effects of hydrothermal carbonization temperature and time on the combustion and kinetics is of great significance, which can also summarize the conditions for efficiency improvement. Herein, the chemical characteristics and surface microstructures of hydrochar and the combustion characteristics, ash fusibility, slagging characteristics, and kinetics of hydrochar pellets were analyzed. The results indicated that the carbon microspheres appeared on the surface of hydrochar from 220 degrees C for 10 min. The combustion characteristics under 180 and 220 degrees C were better than those under 260 degrees C. The slagging tendency of hydrochar pellets was lower than that of wheat straw pellets. It belonged to moderate melting ash and a low slagging rate when HTC conditions equaled or exceeded 220 degrees C for 10 min. Activation energies were moderate under 220 degrees C for 10, 20, and 30 min. Hydrochar pellets had high fuel efficiency under 220 degrees C for 10, 20, and 30 min. The comprehensive combustibility index was positively correlated with hemicellulose and negatively correlated with lignin. The positive correlation was between the cellulose content and the activation energy of the first zone.