Bed Agglomeration during Bio-oil Fast Pyrolysis in a Fluidized-Bed Reactor

This study investigates bed agglomeration during fast pyrolysis of bio-oil in a fluidized-bed reactor at temperatures of 500-800 degrees C. The samples used include bio-oil, bio-oil water-soluble fraction (WSF), bio-oil water-insoluble fraction (WIF), and selected model compounds. Increasing pyrolysis temperature from 500 to 800 degrees C decreases the agglomeration yields of bio-oil, WSF, and WIF from 40% to 15%, 26.2% to 11.6%, and 15.0% to 5.2%, respectively. Investigation using model compounds suggests that the interactions between lignin-derived oligomers and sugar are mainly responsible for the high bed agglomeration yields of bio-oil and WSF, and such interactions weaken as pyrolysis temperature increases. Water has an insignificant effect on bed agglomeration during bio-oil or WSF pyrolysis. The results also show that the bed agglomeration yield and the formation of tar (and/or coke) are in broad linear correlations, indicating that the tar (and/or coke) formed during fast pyrolysis contributes to the bed agglomeration of bio-oil. The linear correlation from the data of bio-oil has a steeper gradient compared to that of WSF and WIF, clearly indicating the synergy taking place between the WSF and WIF during fast pyrolysis in enhancing bed agglomeration.