Integrated Particle- and Reactor-Scale Simulation of Pine Pyrolysis in a Fluidized Bed

We report results from a multiscale computational modeling study of biomass fast pyrolysis in an experimental laboratory reactor that combined the hydrodynamics predicted by a two-fluid model (TFM) with predictions from a finite element method (FEM) simulation of heat and mass transfer and chemical reactions within biomass particles. The experimental pyrolyzer consisted of a 2 in. (5.1 cm) diameter bubbling fluidized bed reactor (FBR) fed with milled pine pellets. The predicted FBR hydrodynamics included estimates of the residence times that the gas and biomass particles spend in the reactor before they exit. A single-particle FEM simulation was constructed on the basis of the geometry and heat transfer properties determined from optical and X-ray computed tomography measurements of wood and char particles collected from the experimental FBR, along with previously proposed pyrolysis reaction kinetics. Taken together, the combined TFM and FEM simulation results predicted net bio-oil yields at the reactor exit that agree well with experimental observations, without any arbitrary fitting parameters. The combined computational models also provided practical information about the most important reactor and feedstock parameters.