Effect of the reactor heating rate on bio-crude yield and quality from hydrothermal liquefaction of different sludge

Abstract

This study scrutinizes the effect of the heating rate obtained in two reactors of different volume (10 mL and 500 mL) on the production of bio-crude during the hydrothermal liquefaction (HTL) process applied to sludges of different nature: a municipal, a paper mill and an agricultural sludge. The effect of the reactor scale on the chemical composition of the bio-crude and the solid residue (co-product of HTL process) is also evaluated by elemental, GC–MS and FT-IR analysis. Results suggest that different heating rates along HTL exert an almost negligible influence on the bio-crude yield and limited effect on the chemical composition when the reaction time under the isothermal conditions is kept at 10 min. In fact, regardless of the heating rate, the bio-crude yields on dry basis from municipal, paper mill and agricultural sludges are equal to 21 %, 21 % and 12 %, respectively. These results could be explained with the different reactive pathway and kinetics of the sludges macro-components.

Keywords

• Sewage sludge
• Industrial sludge
• Bio-crude
• Heating rate
• Hydrothermal liquefaction
• Energetic valorization