Understanding the effect of heating rate on hydrothermal liquefaction: A comprehensive investigation from model compounds to a real food waste

Abstract

Hydrothermal liquefaction (HTL) emerges as an efficient technology for converting food waste into biocrude. Among HTL parameters, the impact of heating rate is understudied. This study systematically explores its variation (5-115 K/min) on HTL performance using actual food waste and model compounds representing its constituents. Results revealed that an increase in heating rates significantly impacts HTL performances (+63 % biocrude and -34 % solid with food waste) with short residence times, as slower heating rates imply a longer overall time and a higher kinetic advancement of the reaction. Conversely, with longer residence times, the influence of heating rates becomes negligible, as kinetics during heating times are overshadowed by those at operating temperatures. A subtle effect of heating variation at extended residence time was observed only with carbohydrates. This research emphasizes the utility of a kinetic severity factor (KSF) as a valuable tool for simultaneously considering heating rates, operating times, and temperatures.

Keywords: Biocrude; Fast hydrothermal liquefaction; Food waste; Heating rate; Kinetic severity factor.