Characteristics of Hydrothermal Carbonization Hydrochar Derived from Cattle Manure

The characteristics of hydrothermal carbonization hydrochar derived from cattle manure including excrements and lignocellulosic biomass were analyzed. The effects of hydrothermal carbonization were evaluated by varying the reaction temperatures in the range of 180~240 °C. The hydrochars were evaluated with respect to their usefulness as renewable fuels via physicochemical analysis and pyrolysis processes. As reaction temperatures increased, the fractions of fixed carbon in proximate analyses, carbon elements in ultimate analyses, and higher heating values of hydrothermally carbonized biochars increased in correlation with the primary reactions of coalification. Various correlations were derived with the characteristics of hydrochars in order to be utilized for operating and designing HTC reactors for cattle manure. The correlation between the O/C and H/C ratios was deduced on the basis of a van Krevelen diagram. The interaction equation was represented with the increased fraction of HHV compared to the reaction temperature of hydrothermal carbonization. The ultimate correlation for the estimation of higher heating values was suggested for HTC hydrochars. Moreover, the pyrolysis characteristics and kinetic parameters of the cattle manure and hydrochar were deduced by utilizing a multi-step kinetic model scheme. As the HTC reaction temperature increased, the global activation energy and the pre-exponential factors of hydrochars decreased in the low-temperature section and increased in the high-temperature section.