Fast pyrolysis is an effective means of converting solid low-energy density biomass to intermediate
energy products, such as bio-oil. In this study, computational fluid dynamics (CFD) simulations of the biomass
fast pyrolysis processes in both the fluidized-bed and the auger reactors were conducted. The
numerical results were validated by experimental data. Materials of all phases were modeled as interpenetrating
continua by use of a multi-fluid model. Chemical reactions were simulated using a multi-step
reaction mechanism that considers multiple compounds in biomass and various gaseous species in the
reactor. In the study of biomass fast pyrolysis in the fluidized-bed reactor, CFD simulation results were
analyzed to obtain the average residence time of materials in the reactor. This residence time was used
as the time for chemical reactions in estimating the final product yields. The estimated product yields
agreed well with the experimental data. To simulate the complex geometry and fluid dynamics in the
auger reactor, a numerical approach based on a rotating reference frame was incorporated into the multi-
fluid model to account for the auger rotation. Good levels of agreement between the predicted and
measured product yields were obtained. A parametric study was conducted to characterize the effects
of operating conditions on product yields. The study shows that the optimal wall temperature for maximum
tar production was approximately 823 K. The tar yield decreased with increased pre-treatment
temperature of the biomass feedstock. It was also found that increased inlet nitrogen flow rate was beneficial
to tar yield, while increased biomass feed rate had a negative effect on tar production.