A numerical study of gas–solid flow hydrodynamics in a riser under dense suspension upflow regime.

The Eulerian–Eulerian two-fluid model coupled with the EMMS/Matrix drag model was employed to investigate the gas–solid flow hydrodynamics in the riser of high-density circulating fluidized bed using Geldart B particles under the dense suspension upflow (DSU) regime. Based on the 2D simulations of two test cases, the predicted axial and radial profiles of solid volume fraction agreed well with the experimental observations, and it could capture the key characteristics of the DSU regime. The transient solid flux and the power spectral density of pressure fluctuation were discussed. The 2D simulation results using the EMMS/Matrix and the Gidaspow drag models were compared in details, and the EMMS/Matrix drag model gave better radial distributions against experimental data, but the predicted radial profiles were improved by solving partial differential equation of granular temperature with the Gidaspow drag model. The 3D simulation with the EMMS/Matrix drag model was also performed, and the differences in the predicted axial and radial profiles of solid volume fraction between 2D and 3D simulations were not significant. The two-dimensional two-fluid model with the EMMS/Matrix drag model is applicable to the simulation of gas–solid flow in the riser under the DSU regime. [ABSTRACT FROM AUTHOR]