Comparison of solid phase closure models in Eulerian-Eulerian simulations of a circulating fluidized bed riser

Abstract

In this work, computational fluid dynamics with Eulerian-Eulerian modeling approach is used in the investigation of the effect of the solid phase closure models on the hydrodynamics of a circulating fluidized bed riser. The studied models are the kinetic theory of granular flow and the powder modulus model. Computational performance and model prediction accuracy are investigated by performing transient simulations for three different cases and for different mesh sizes. The modeling results are compared with measured vertical pressure profile, external circulation mass flow rates, and particle velocity and concentration profiles obtained from a laboratory scale circulating fluidized bed unit. Additionally the computational times are compared to estimate the computational performance and to investigate if a simpler set of closures is computationally more affordable. The results indicate that both closure models can give good predictions for some quantities, while lacking in other quantities. The results indicate that the closure models for the solid phase have a noticeable effect on the model predictions, such as the vertical pressure profile and external circulation rate of the particles.