Fractional Condensation of Sawdust Pyrolysis Vapors: Separation of Complex Components, Enhancement of Bio-Oil Properties, and Life Cycle Assessment

Abstract

This study investigates the fractional condensation of multicomponent vapors obtained from the pyrolysis of sawdust. Employing a fluidized bed reactor, the sawdust underwent fast pyrolysis at 500 °C, and the resulting pyrolytic vapors were subjected to fractional condensation using a temperature-controlled system of four condensers. The objective was to assess the effectiveness of this fractional condensation system in separating complex components and enhancing bio-oil properties. Characterization of the bio-oil included evaluating pH value, total acid number (TAN), heating value, and chemical compositions. The findings revealed that the last two condensers effectively collected most of small molecular chemicals such as acetic acid, ketones, esters, alcohols, aldehydes, and water. Notably, Benzenes (benzene, toluene, and ethylbenzene) and certain types of phenols (creosol and Phenol, 2,3-dimethyl-) tended to condense in SBO 1, as their temperatures were higher than their dew points. SBO 1 exhibited the highest calorific value of 29.42 MJ/kg, whereas SBO 2 displayed the lowest acidity (1.19 mol/L) and a higher calorific value (11.38 MJ/kg) compared to SBO 3 and SBO 4. Additionally, a life cycle assessment (LCA) demonstrated that the fractional condensation method possesses economic and environmental advantages. This approach offers a promising technique for effectively separating complex components in bio-oil derived from sawdust pyrolysis, leading to improved product properties and reduced environmental impact. Consequently, these findings contribute to the advancement of sustainable biomass conversion processes and underscore the potential for optimizing the production of valuable bio-based products.

Keywords: Bio-oil, pyrolysis, Fractional condensation, LCA