Evaluating combustion characteristics and combustion kinetics of corn stover-derived hydrochars by cone calorimeter

Abstract

This study investigated the combustion properties of corn stover-derived hydrochars using cone calorimeter. Hydrochars were prepared by hydrothermal carbonization (HTC) at 200, 230, and 260 °C for 30 min. Six different heat fluxes (5–50 kW/m2) were applied to hydrochars to determine critical heat flux (CHF), ignition temperature, thermal response, peak heat release rate (pHRR), thermal hazard risk, and combustion efficiency. Results show that increasing the HTC temperature decreased the CHF and ignition temperature but increased the thermal resistivity. Increasing the heat flux decreased the thermal resistivity and ignition time of all the hydrochars. Thermal hazard analysis indicated that the hydrochars posed lower thermal risk than raw corn stover. Finally, combustion kinetics were proposed using two parallel first order reactions for volatile matters and fixed carbon. The reaction rate of volatile matter was significantly higher than the reaction rate of fixed carbon. HTC increased the fixed carbon activation energies to as high as 24.0 MJ/mol. Overall, HTC forms hydrochars which are less flammable, more stable, and a lower thermally risk material for piloted ignition than raw corn stover.