Gas-Solid Turbulent Flow in a Circulating Fluidized Bed Riser; Numerical Study of Binary Particle Mixtures

A numerical simulation was performed on a turbulent gas-particle multi-phase flow in a circulating fluidized bed riser based on a hard-sphere discrete particle model (DPM) for the particle phase and the Navier-Stokes equations for the gas phase. The sub-grid scale stresses (SGS) were modeled with the SGS model proposed by Vreman (2004). The model enables the calculation of an arbitrary particle size distribution. In this work, binary mixtures of particles with different diameters are used in the simulation. From the numerical results it is found that the particles display a radial and axial diameter distribution. Small particles have a higher vertical particle velocity than the large particles. With increasing superficial gas velocity, the vertical particle velocity is increased. The average particle velocity and concentration vary both in the radial and axial directions. Finally, the numerical results are compared with the experimental and numerical results of Mathiesen et al (2000).