Insights into Preventing Fluidized Bed Material Agglomeration in Fast Pyrolysis of Acid-Leached Pine Wood

Acid leaching of lignocellulosic biomass prior to fast pyrolysis can increase the bio-oil yield and improve bio-oil quality. However, fast pyrolysis of acid-leached biomass in fluidized bed reactors can lead to bed material agglomeration. A series of experiments were conducted to investigate how pyrolysis conditions and torrefaction pretreatment affected fast pyrolysis of acid-leached pine wood to gain insights into understanding and preventing this issue. Melting of the acid-leached wood during fast pyrolysis resulted in the formation of bed material agglomerates, which eventually caused defluidization of the reactor. Three approaches to preventing this issue were investigated in this study. Lowering the pyrolysis temperature to 360 °C limited the conversion of the lignin and prevented bed agglomeration. Using a high sand feeding rate to continually refresh the bed material prevented melted biomass material from accumulating and causing agglomeration. Torrefaction pretreatment of the acid-leached wood resulted in structural changes that altered the pyrolysis behavior of the lignin and also prevented bed agglomeration. Each of these approaches had a different effect on the yield of the bio-oil product but had a minimal impact on its quality.