Modeling and simulation of flows in two-phase fluidized systems

Abstract

This present work aims to investigate the solids motion and fluid flow in a two phase fluidized bed via a discrete particle modeling and simulation. The motion of individual particle is based on the fluid force acting on the particle and the contact force between particles. The contact force is models by using the same analogy of spring, dash-pot and friction slider. In addition, the mixing and segregation in beds containing two types of particles with different densities and different size are also studies. Moreover, the effects of superficial gas velocity and bad geometry on the solids movements are also investigated. A solids circulation cell is found when the bed reaches at steady state. The solids ascend at the center with high velocity and descend with low velocity near the wall. The simulation solids flow pattern agrees well with the experimental result obtain by Moslemian (1987). The solids distributions in the bed containing the particles with the density ratios of 1.4 and 1.25 show good mixing. On the other hand the bed with the particle density ratio of 2.5 shows segregating behavior. Similarly, the beds containing the particles with the size ratios of 1.33 and 2.0 show mixing behavior and segregating behavior, respectively. These results obtained from simulation were found to follow the mixing/degregation criteria obtained experimentally by Tanaka et al. (1996). The solids mixing and segregation are not significantly dependent on the superficial gas velocity. The findings of the simulation i.e., solids movement and distribution will be information for understanding the hydrodynamics, mass and heat transfer leading to successfully design and operation of the system. The knowledge of this modeling and simulation is applicable to study the phenomena in the system concerned with granular materials such as multiphase flow reactor and dryer.