CFD modeling of the effects of particle shrinkage and intra-particle heat conduction on biomass fast pyrolysis

This study numerically characterizes the combined effects of particle shrinkage and intra-particle heat conduction on biomass fast pyrolysis using computational fluid dynamics (CFD). The so-called multi-fluid model (MFM) was employed to simulate hydrodynamics and biomass fast pyrolysis was modeled by a lumped kinetics. The particle shrinkage and intra-particle heat conduction were modeled through modification of the diameter of biomass phases and reaction rate constant. Four cases with different combinations of particle shrinkage and intra-particle heat conduction were designed and their performances regarding product yields were compared. The hydrodynamics and reaction behaviors in the reactor were predicted. The distributions of particle diameter and density, product yields, and char properties were analyzed and compared with the experiments. The mechanisms for the effects of these two models were revealed. Both the particle shrinkage and intra-particle heat conduction effects lead to lower tar yield and higher char yield. The predicted product yields considering both models are in the best agreement with the experiment results. (C) 2019 Elsevier Ltd. All rights reserved.