Effects of separation methods on yield and quality of biocrude after thermochemical liquefaction of marine microalgae

Hydrothermal liquefaction (HTL) is a promising process for conversion of microalgae to biocrude that is upgradable to liquid transportation fuel. However, there is yet to be established standard separation method for product recovery. In this paper, the effects of separation methods on yields and quality of biocrude were investigated. HTL studies were conducted at operating conditions of 350oC and 5min with solids loading of 16wt%. The results shows that multistep extraction of product mixture led to ~65wt% biocrude yield compared to ~48wt% for single step. Multistep extraction led to increase in biocrude yield, with lower yields in solid residue and aqueous phases. However with the trade-offs of nitrogenous and oxygenated compounds in biocrude. Quality of biocrude was improved after vacuum evaporation of biocrude phase at 100oC when compared to evaporation at 40oC. The separation methods had little impact on biocrude energy density, which varies between 34MJ/kg and 38MJ/kg, 1.5 and 1.7 for hydrogen-to-carbon atomic ratios.Keywords: Biocrude; Energy; Hydrothermal liquefaction; Microalgae; Separation methods