(507e) Hydrophobic Behavior of Hydrothermally Carbonized Biomass

Hydrothermal Carbonization (HTC) is an emerging thermochemical processing technology, where biomass is converted to low-ash, carbon-rich, energy-dense hydrochar. Pelletization of hydrochars could have a significant advantage for biorefinery industries. The objective of this study was to synthesize raw and hydrochar pellets using benchtop pellet press to increase its mass and energy density, analyze its various fuel properties, e.g. proximate analysis, chemical composition of the sample, e.g. ultimate analysis, and develop a model correlating Equilibrium Moisture Content (EMC) and hydrophobicity. Corn stover high ash fraction (CS HAF), resulting from air-classification technology, was used as feedstock for HTC in this study. The raw HAF contains around 10.5 % ash. HTC of CS HAF was performed at three different temperatures (200, 230 and 260 °C) for 30 min. Ash content of the raw sample and hydrochars were measured by following ASTM D1102 method. Thermogravimetric Analyzer (TGA) was used to determine the fixed carbon and volatile content. CHNS/O analyzer was used to determine the Carbon (C), Hydrogen (H), Nitrogen (N), Sulfur (S), and Oxygen (O) content in the hydrochars. van-Soest fiber analysis was performed to determine effect of HTC on extractives, hemicellulose, cellulose, and lignin. Multiple pellets of each type of sample (raw, HTC 200, HTC 230 and HTC 260) were prepared in a single-press pellet press with 13 mm die at 20 ton pelletization pressure and room temperature. Mass and energy densities were measured of the pellets. Moreover, five different combinations of raw CS LAF (Corn Stover Light Ash Fraction) and CS HAF HTC 260, for instance, 90%-10%,80%-20%, 70%-30%, 60%-40%, 50%-50% (weight ratios) samples were prepared. Scanning Electron Microscope (SEM) was used at higher magnification to visualize the arrangement of hydrochar particles over the raw fibers in the heterogeneous pellets. Contact angle and water droplet diameter on the surface of the pellets were measured using goniometer. The EMC for raw and heterogeneous hydrochar pellets were determined in six different humid conditions created by six different supersaturated salt solutions in the water bath. Overall, the results showed that with the increase of HTC temperatures, the mass yield and ash yield decreased. Although the hydrophobicity increased with the decrease of the raw CS LAF and CS HAF HTC 260 ratio, there is an optimum ratio after which the pellet shows hydrophilicity. Finally, a model correlating EMC and hydrophobicity was established.