Physicochemical, Pyrolytic, and Combustion Characteristics of Hydrochar Obtained by Hydrothermal Carbonization of Biomass

Effects of the type of biomass and temperature, with longer residence time, on physicochemical characteristics of hydrochar were investigated. Different carbonization conditions were applied with the goal of producing hydrochars having better physicochemical properties. After the carbonization process, the pyrolysis and combustion behaviors of hydrochar were evaluated. The effect of temperature on the chemical characteristics of hydrochar was obvious. The yield and heating value of hydrochar were high for raw materials. Even though the yield of hydrochar from water hyacinth was low, the morphology of this hydrochar was the best among all biomass samples tested. Hydrochar derived from water hyacinth can be used as a new kind of carbon material, which can improve the utilization of biomass resources. The pyrolysis and combustion behaviors of hydrochar were studied; the corresponding kinetic parameters were determined by thermogravimetric (TG) analysis. With increasing heating rate, the TG and differential thermogravimetric (DTG) curves moved to high temperatures. The combustion of hydrochar had two stages: volatilization and fixed carbon combustion. The activation energy of the wheat straw was 37 kJ/mol, and the activation energy of the water hyacinth was 51 kJ/mol. This data indicated that the combustion of water hyacinth hydrochar was difficult.