(98c) Evaluation of Drag Models for Gas-Solid Fluidization of Geldart a Particles in All Flow Regimes

Coarse grid two-fluid simulation of gas-solid fluidized bed reactors based on the kinetic theory of granular flow exhibits a significant dependence on drag models, especially for Geldart A particles. Inappropriate selection of drag models leads to inaccurate fluidization behavior predictions. This study focused on the evaluation of drag models derived from different methods for 3D two-fluid model simulations of gas-solid fluidization of Geldart A particles in bubbling fluidization, turbulent fluidization, fast fluidization and dilute phase transport regimes. Eight candidate drag models were selected, which included five heterogeneous drag models and three homogeneous drag models that belong to six types. Comparison with available experimental data clearly demonstrates the need for modification of homogeneous drag models to account for the effect of mesoscale structures (bubble and cluster). The Sarkar drag model and EMMS drag models are found to achieve superior predictions in all fluidization regimes, while the other drag models are found to be capable of predicting fewer fluidization regimes. The results of this work provide a guideline for choosing appropriate drag models for simulating Geldart A particles and provide suggestions on developing more reliable and general drag models applicable in all flow regimes.