(753e) Co-Pyrolysis of Plastics and Biomass Waste

Fast pyrolysis has been demonstrated previously for conversion of mixed waste constituents such as pine, sugarcane bagasse, corn stover, various plastics, and mixtures thereof into value-added liquid bio-oil fuel, biochar, and combustible gases. This process reduces the waste stream volume by up to 98% with low emissions and minimal impact on the environment. In an effort to understand the interactions between biomass and fossil-derived plastics, several pine/polystyrene(PS) binary mixtures were pyrolyzed in a bench-scale (1 kg/h), continuous, bubbling fluidized bed reactor at temperatures between 500 °C and 650 °C. Bio-oil properties from pyrolysis of pine/PS mixtures of 70%/30%, 80%/20%, and 90%/10% by mass were measured to determine the effect of plastic concentration on heating value, moisture content, and viscosity. Fractional condensation of heavier and lighter bio-oil fractions was demonstrated with two condensers in series, which allowed for the condensing temperature to be varied for collecting different oil fractions. The fluidizing gas temperature, residence time, reactor bed temperature, and condensing temperatures were varied to determine the effects on collection efficiency and bio-oil product characteristics such as heating value, viscosity, and water content. Samples of the bio-oil product were collected at each condenser and analyzed using gas chromatography coupled with mass spectrometry (GC/MS). Addition of plastics to the feedstock appears to have prompted a shift in bio-oil composition that indicates some interaction between the PS and pine pyrolysis intermediates. Significantly more aromatics were formed with the mixtures than when pine was pyrolyzed alone. The lower temperature fractions contained an abundance of the styrene monomer while the higher temperature fractions contained significantly heavier aromatics, including tolylacetic acid, bibenzyl, α-methylbibenzyl, and 6-phenyl-2-hexenal. Future work is focusing on catalytic upgrading of the heavier and lighter bio-oil fractions.