Characterization of bio-oil recovered as stage fractions with unique chemical and physical properties

Bio-oil from fast pyrolysis of biomass consists of hundreds of compounds with a wide range of molecular weights. These include both volatile and non-volatile compounds and viscous oligomers, which complicates recovery of the liquid product from vapors and aerosols generated during pyrolysis. We have developed a bio-oil recovery system that overcomes the fouling problems that commonly occur in conventional condensers, allowing recovery of stage fractions (SF) of bio-oil with distinctive chemical and physical properties. The concept has been evaluated in an 8 kg/h process development unit (PDU) consisting of a fluidized bed pyrolyzer, hot cyclones, and a series of condensers and electrostatic precipitators (ESPs) that recover five stage fractions. Red oak was pyrolyzed in the PDU and the resulting stage fractions of bio-oil analyzed for moisture, modified acid number (MAN), water insoluble content, solids content, higher heating value (HHV), kinematic viscosity and chemical composition.

► A bio-oil recovery system was developed that recovers bio-oil as stage fractions.
► The bio-oil stage fractions have distinctive chemical and physical properties.
► The first two stages concentrated water soluble sugars and water insoluble “pyrolytic lignin”.
► Most of the water and acetic acid traditionally found in bio-oil was driven to the last stage fraction.