Modeling of Axial-Symmetric Flow Structure in Gas–Solids Risers

Pneumatic transport of solids in a riser has a unique nonuniform flow structure, characterized by the core solids acceleration and the wall solids deceleration along the riser, which causes the down-flow of solids and hence back mixing. To predict this nonuniform flow structure, this paper presents a mechanistic model that includes two controlling mechanisms: the interparticle collision damping for axial transport of solids and the effects of collision-induced diffusion and turbulent convection for radial transport of solids. The model predictions are partially validated against available measurements, such as axial and radial distributions of concentration and velocity of solids.