(736e) Triple Phase Simulation of Bubbling Fluidized Beds of Geldart “a” Particles with a Bubble-Based Drag Model

 

Teng Wang, Caixia Chen*

Key Laboratory of Coal Gasification and Energy Chemical Engineering of Ministry of Education, East China University of Science and Technology, Shanghai 200237, China

Abstract

The Eulerian-Granular two-fluid model (TFM) has been employed in the simulations of the gas-solid hydrodynamics of fluidized beds, its application for Group â??Aâ? particles was barely successful unless very fine grid sizes and very small time steps were used in the computations. To make the TFM model work for coarse-grid simulations, Modifications of the interphase drag force are required. In this presentation, we report a triple-phase numerical model for the simulations of gas-solid bubbling fluidized beds with Geldart â??Aâ? particles. In the model, the gas-solids suspension was modeled as a primary gas phase presented in the emulsion, a secondary gas phase presented in the bubble, and a third phase consisting of solids. A bubble-based drag model was derived taking into account of the heterogeneous flow structures of the emulsion phase. The KTGF model was used to describe the solid phase stresses. Simulations were conducted for two different scales bubbling fluidized beds of Group â??Aâ? particles. Mesh independences were confirmed up to a radial grid size of 200 times particle diameter, and the sensitivity of the transitional results on the time-steps was investigated. The predicted bed expansion and the voidage distribution, axial and radial solids volume fraction profiles, and the solids velocity vectors have been validated against literature data. The bubbly motion of the gas and the gross circulation of solids were simulated. The heterogeneous properties of emulsion phase were captured using mesh size of the order of 50 particle diameters for a 0.19 m diameter bed. For a 0.296 m diameter bed, a mesh size of 200 d_pwas capable of capturing the time-averaged hydrodynamics without losing accuracy.

Key words: triple-phase simulation; Group A particle; gas-solid bubbling bed; bubble-based drag model; KTGF closure.

Highlight

• A triple-phase model is developed for gas-solid fluidized bed of Group â??Aâ? particles.
• A bubble-based drag model is derived and validated with benchmark simulations.
• The bubbly motion of gas and the gross circulation of solids are simulated.
• Grids independence is confirmed up to a radial size of 200 times particle diameter.

*Correspondence Author. Tel: +86 021 64252057.

Email address: cxchen@ecust.edu.cn