Evaluation of fuel and combustion properties of hydrochar derived from Co-hydrothermal carbonization of biomass and plastic

Abstract

Co-hydrothermal carbonization (Co-HTC) thermochemically transforms multiple solid feedstocks into energy-dense hydrochar. Herein, this study investigated the corn stover-polyurethane mixture at various feedstock ratios (5–15% polyurethane and balance corn stover) on fuel and combustion properties of the hydrochar prepared at various Co-HTC conditions. Results indicate that Co-HTC shows lower mass yield than control HTC with corn stover only, however, it shows significant improvement in energy densification (7.8–34.5%) and fuel ratio (0.22–0.64). The thermogravimetric analysis shows that Co-HTC-derived hydrochars are more thermally stable compared to raw corn stover. The combustion properties evaluated by cone calorimeter indicate that the Co-HTC-derived hydrochars have maximum 1.3 times the peak heat release rate of raw corn stover. The Co-HTC-derived hydrochars along with raw corn stover and control hydrochar persist in smoldering phase (slow combustion) of combustion while raw polyurethane persists in flaming phase (fast combustion). Moreover, Co-HTC-derived hydrochars show relatively lower combustion efficiencies (49.2–75.2%) than raw corn stover (77.2–89.9%) or control hydrochar (75.2–77.9%). In addition, increasing polyurethane percentage in the corn stover-polyurethane mixture could reduce the combustion efficiency of hydrochar.