Fractional condensation of bio-oil vapors from pyrolysis of various sawdust wastes in a bench-scale bubbling fluidized bed reactor

Abstract

The use of lignocellulosic waste as an energy source for substituting fossil fuels has attracted lots of attention, and pyrolysis has been established as an effective technology for this purpose. However, the utilization of bio-oil derived from non-catalytic pyrolysis faces certain constraints, making it impractical for direct application in advanced sectors. This study has focused on overcoming these challenges by employing fractional condensation of pyrolytic vapors at distinct temperatures. The potential of five types of sawdust for producing high-quality bio-oil through pyrolysis conducted with a bench-scale bubbling fluidized bed reactor was investigated for the first time. The highest yield of bio-oil (61.94 wt%) was produced using sample 3 (damaged timber). Remarkably, phenolic compounds were majorly gathered in the 1st and 2nd condensers at temperatures of 200 °C and 150 °C, respectively, attributing to their higher boiling points. Whereas, carboxylic acid, ketones, and furans were mainly collected in the 3rd (−5 °C) and 4th (−20 °C) condensers, having high water content in the range of 35.33%–65.09%. The separation of acidic nature compounds such as acetic acid in the 3rd and 4th was evidenced by its low pH in the range of 4–5, while the pH of liquid collected in the 1st and 2nd condensers exhibited higher pH (6–7). The well-separated bio-oil derived from biomass pyrolysis facilitates its wide usage in various applications, proposing a unique approach toward carbon neutrality. In particular, achieving efficient separation of phenolic compounds in bio-oil is important, as these compounds can undergo further upgrading to generate hydrocarbons and diesel fuel.