INFLUENCE OF THE GRANULAR TEMPERATURE IN THE NUMERICAL SIMULATION OF GAS-SOLID FLOW IN A BUBBLING FLUIDIZED BED

Abstract

This article describes a mathematical model and numerical simulation of gas-solid flow in a bubbling fluidized bed (BFB), where the the two-fluid Eulerian-Eulerian model was used and the solid phase stress tensor was modeled considering both the friction between particles and the kinetic theory of granular flows. The code MFIX (Multiphase Flow with Interphase eXchanges) developed by NETL (National Energy Technology Laboratory, U. S. Department of Energy) was used for numerical simulations, and the results were obtained through computing the granular temperature by using a partial differential equation (PDE) or an algebraic expression. More realistic results were obtained when a PDE with boundary conditions of the partial slip was used. However, for computing the granular temperature in the case of fine grids, it is recommended to use the algebraic equation because it will save computational effort in simulations. Variation in the diameter of the particles (Group B and Group A/B) was also analyzed, and, consequently, it was observed that in future analysis a term for capturing the influence of cohesive forces should be added for particles of Group A/B. This study has revealed that a smooth transition between the viscous regime and the plastic regime is necessary for simulating a hydrodynamic bubbling fluidized bed.