Biomass to oil: Fast pyrolysis and subcritical hydrothermal liquefaction
Résumé
The present paper deals with the comparison of two biomass-to-oil processes: fast pyrolysis and subcritical hydrothermal liquefaction. Using the same biomass (beech sawdust), fast pyrolysis was led thanks to a cyclone reactor (wall temperature between 870 and 1040 K) and subcritical hydrothermal liquefaction thanks to a 150-ml-batch-reactor (temperature between 420 and 600 K). Mass balances and phases analysis (ultimate analysis, higher heating value (HHV), Karl-Fischer, gas chromatographies, H1 NMR) allow the comparison of both processes and the characterization of pyro-oils (heavy oils, light oils and aerosols), liq-oils (heavy oils and water soluble organics), solids and gas. For both processes, there is a temperature for which a high conversion of biomass is reached with a minimum of gas mass yield. Up to 62.6 wt% of pyro-oil and 47.0 wt% of liq-oil, on dry basis, were obtained in this work, with oxygen contents and chemical compositions different from one to the other.