Hydrodynamics of Bubbling Fluidized Beds for Biomass Gasification: Influence of Particle-drag within an Eulerian Granular Model

Particles’ mixing and segregation have a strong influence on the performance of fluidized bed reactors for gasification and pyrolysis. The interaction forces between phases are crucial for modeling mixing and segregation. The nature of particle characteristics such as shape are also very important to consider for accurate modeling. In this work, the hydrodynamic study of binary mixture of biomass and sand is conducted in a 2-D fluidized bed using Computational Fluid Dynamics (CFD) based on the concept of Euler–Euler two-fluid combined with Kinetic Theory of Granular Flow (KTGF). Modified drag models of Gidaspow and Syamlal–O'Brien are used to determine the drag force between the two phases and the results are compared with the experimental data in literature. The default Gidaspow and Syamlal–O'Brien drag models failed to predict the experimental fluidization behavior. In comparison, the modified models show very good agreement with experiments in terms of pressure drop estimation and particle distribution in the bed. Syamlal–O'Brien model predicted the pressure drop very well, but failed to capture accurate mixing and segregation phenomenon. The Gidaspow model was found to provide better agreement with the experimental results of time-averaged biomass mass fraction along the bed height.