Computational fluid dynamics for dense gas-solid fluidized beds

Abstract

Abstract Many computational fluid dynamics (CFD) models for describing the hydrodynamics of dense gas-solid flows in fluidized beds have been put forward in the past few decades. These models treat the solid phase as continuum or discrete particles, which leads to Eulerian-Eulerian or Eulerian-Lagrangian formulations, respectively. Different governing equations and closure relations essentially result from an insufficient understanding of the complex gas-particle and particle-particle interactions for gas-solid flows. The current status of these models is discussed briefly in this paper. All the approaches in the literature modify only the solid phase momentum balance equcation introducing various forms of the solid phase stress tensor and the solid phase pressure drop in the Eulerian-Eulerian models. Taking them into consideration, a new model for predicting the fluid behavior of dense gas-solid flows in fluidized beds has been developed, which contains new terms in both the particle and gas phase momentum balance equations and requires only the use of an experimental drag force correlation. Several results are shown to verify the model's reliability, which include the homogeneous fluidization of Geldart type A particles, the bubbling and jetting fluidization of Geldart type B particles in rectangular beds, and fluid dynamics in a complicated geometry for a bubbling-bed of a fast internally circulating fluidized-bed biomass gasifier.