Characteristics of Bio-Oils Produced by an Intermediate Semipilot Scale Pyrolysis Auger Reactor Equipped with Multistage Condensers

The pyrolysis vapor produced from pine wood using an intermediate pyrolysis auger reactor (72 s of solid residence time at 500, 525, and 550 °C) was condensed by three different temperature-profiled condensers. The first condenser had a surface temperature of 60–85 °C and a vapor temperature of 126–193 °C, whereas the second condenser had a surface temperature of 40–60 °C and a vapor temperature of 107–126 °C. The surface temperature of the third water-cooled condenser was ≤25 °C, and the vapor temperature was ∼33–99 °C. The water content was very low (11.1–13.9 wt %) in the bio-oil generated by the first condenser; however, it significantly increased in the bio-oil from the second (28.3–39.2 wt %) and third condensers (52.0–64.0 wt %), which led to the bio-oils with lower viscosities and densities. As the pyrolysis temperature increased, the water-insoluble fraction of the bio-oil was the highest (44–47 wt %) in the first condenser and was significantly lower in the second and third condensers (17–27 wt %). The weight-average molecular weight (<i>M</i>_w) was higher (369–423 g/mol) in the first condenser than in the second and third condensers (275–296 g/mol). Most of the levoglucosan condensed in the first condenser. As the pyrolysis temperature increased from 500 to 550 °C, the water content and total acid number (TAN) decreased in each condenser, whereas the insoluble fraction and weight-average molecular weight (<i>M</i>_w) increased in each condenser. Acidic compounds mainly condensed in the second condenser by their dew point and density, whereas a large amount of furans, aldehydes, ketones, alcohols, and phenolic compounds condensed in the first condenser