1 Fluid Mechanics and Combustion, The Faculty of Engineering and Science, Aalborg University, VBN2 Department of Energy Technology, The Faculty of Engineering and Science, Aalborg University, VBN3 The Faculty of Engineering and Science (ENG), Aalborg University, VBN4 Section of Chemistry, The Faculty of Engineering and Science, Aalborg University, VBN5 Supramolekular Chemistry, The Faculty of Engineering and Science, Aalborg University, VBN6 Department of Chemistry and Bioscience, The Faculty of Engineering and Science, Aalborg University, VBN7 Tianjin University8 Tianjin University
Effects of reaction temperature and aqueous phase recirculation
Hydrothermal liquefaction (HTL) of barley straw with K2CO3 at different temperatures (280–400 C) was conducted and compared to optimize its process conditions; the aqueous phase as a co-product from this process was recycled to explore the feasibility of implementing wastewater reuse for bio-crude oil production. Results showed that low temperature favored the formation of bio-crude oil, with a maximum yield of 34.9 wt% at 300 C. Contrarily, at high temperature, the bio-crude oil had better qualities in terms of less oxygen content and higher heating values (HHVs). The compounds identified in bio-crude oil were mainly phenolics, carboxylic acids, aldehydes and alcohols, among which the relative contents of phenolics and carboxylic acids decreased with increasing temperature. In the recirculation studies, bio-crude yield was enhanced gradually with aqueous phase addition at 300 C, and reached 38.4 wt% after three cycles. The HHVs of bio-crude oil from HTL with aqueous phase were 28.4–29.4 MJ/kg, slightly higher than those from HTL with fresh water. While no obvious differences in elemental distribution can be found after aqueous phase recirculation. In conclusion, this study gives a detailed insight into the HTL behavior of barley straw, and offers potential opportunities and benefits for bio-crude oil production through the reuse of aqueous phase.