Abstract: Hydrothermal carbonization experiments were carried out at 180-290℃ for 30-480 min using corn stalk as raw material. The carbon content and pyrolysis characteristics of corn stalk at different reaction conditions were studied. The pyrolysis process and the kinetic parameters of corn stalk and its hydrochar (250℃, 480 min) were investigated using the Friedman method, Flynn-Wall-Ozawa (FWO) method and Kissenger-Akahira-Sunose (KAS) method. The results indicated that the carbon content of corn stalk hydrochar increased with increasing reaction severity. The pyrolysis yield and the maximum reaction rate of the hydrochar decreased gradually, and the pyrolysis temperature range corresponding to the maximum reaction rate varied from 280-380℃ to 400-450℃ with the increase of reaction severity. When the reaction severity was larger than 7.11 (250℃, 480 min), the maximum reaction rate was relatively stable. The thermal decomposition processes of both the corn stalk and its hydrochar could be divided into three stages:dehydration, main pyrolysis and carbonization. The activation energies calculated by both FWO and KAS method were similar. At high conversion stage (greater than 20%), the activation energies of the hydrochars were much higher than that of corn stalk. When the conversion rate was 75%, the activation energies of the hydrochar calculated by FWO and KAS method were 260.87 and 261.84 kJ/mol, respectively, while the activation energies of corn stalk were only 145.55 and 142.74 kJ/mol, respectively.

Key words: corn stalk, hydrochar, thermogravimetric, kinetic, activation energy