Effect of hydrothermal carbonization temperature on fuel properties and combustion behavior of high-ash corn and rice straw hydrochar

Abstract

Hydrothermal carbonization (HTC) has been proven to improve the fuel properties of low-ash straw biomass. To explore the effect of HTC on high-ash straw biomass, the fuel properties and combustion behavior of hydrochar prepared by high-ash rice straw and corn straw at different temperature were studied. The results showed that increased reaction temperature could improve the C content, fixed carbon, heating value and fuel ratios (FC/VM) in high-ash straw hydrochars, which is similar to the change trend of low-ash biomass. The hydrochar prepared at 260?C has similar H/C and O/C atomic ratios and FC/VM to lignite. In addition, the highest energetic recovery efficiency is obtained at 200?C. While at 180?C, the comprehensive combustion characteristic index of the hydrochar is the best, which is 5.04?10-11 (min-2?K-3) and 6.42?10-11 (min-2?K-3). In addition, the C content in the hydrochars at 180?C was lower than the raw material, and the ash content increases with the reaction temperature, which is quite different from the low-ash biomass. In conclusion, the HTC could improve the fuel quality of high-ash straw, while its ash content remains at a high level.

Investigation of the Effects of Cohydrothermal Carbonization on the Physicochemical Characteristics and Combustion Behavior of Straw Hydrochars

“…Co-HTC Experiments: The results of a previous single-straw biomass HTC experiment revealed that the hydrochar produced at 180 °C had the highest yield, a higher energy yield, and the best comprehensive combustion characteristic index and flammability index, while the hydrochar prepared at 260 °C had higher carbon content, lower hydrogen and oxygen content, and a higher HHV, fuel ratio, and energy density. [42] In addition, from the perspective of combustion activation energy, the optimal hydrothermal treatment temperature should be 260 °C. [42] Therefore, in this study, the reaction temperatures used in the Co-HTC experiment with multiple-straw crops were 180 °C and 260 °C.…”

“…[ 42 ] In addition, from the perspective of combustion activation energy, the optimal hydrothermal treatment temperature should be 260 °C. [ 42 ] Therefore, in this study, the reaction temperatures used in the Co‐HTC experiment with multiple‐straw crops were 180 °C and 260 °C.…”