Abstract
A pilot-scale continuous flow reactor (CFR) was modified for hydrothermal liquefaction (HTL) of algae slurry under subcritical conditions to investigate the feasibility of scaling up from batch to continuous processing. Modifications included a novel dual filter system that can remove solids at system pressure and temperature, and undergo in-situ cleaning. Commissioning was carried out to address potential particle settling and clogging problems, and to estimate reactor transport characteristics. CFR performance was evaluated by running 31.4 L algae slurry with solids loadings of 3-5 wt.% under 325-350 °C and 18 MPa for 7 h. C and N elemental yields in HTL aqueous phase reached 39.0 wt.% and 61.8 wt.%, respectively. Future improvements to the CFR system will focus on higher solids loading and addition of in-line HTL liquid upgrading capabilities following the filtration system. •A high-temperature, high-pressure filtration system was designed to remove solids from HTL liquid/gaseous products at near reaction conditions to keep heavy oils in the liquid phase.•Uninterrupted reactor operation was achieved by cycling between the dual filter systems and performing in-situ filter cleaning.•Measured reactor residence time distributions were narrow and close to the calculated theoretical mean time.