Effect of Inlet Boundary Conditions on Computational Fluid Dynamics (CFD) Simulations of Gas–Solid Flows in Risers

Abstract

The effect of type of inlet conditions on the predictions of Eulerian–Eulerian simulations of a circulating fluidized bed riser has been investigated in both 2D and 3D domains. The 2D simulations were conducted using 3 different inlet configurations: (A) solids entering in radial direction from a two-sided inlet and gas entering axially from the bottom inlet, (B) solid entering axially from a two-sided bottom inlet near the wall and gas entering axially from a bottom inlet at the center, and (C) gas phase entering axially from a two-sided bottom inlet near the wall and solids entering axially from a bottom inlet at the center. In 2D simulations, it was found that both time-averaged axial velocity and solids volume fraction radial profiles were functions of the inlet kinetic energy as well as gas–solid mixing patterns at the inlet. Whereas 2D simulations using boundary conditions A and C showed significant deviations from experimental profiles, the boundary condition B as well as full-scale 3D simulations gave reasonable agreements with experimental observations.