Study of Parameters Effect on Hydrodynamics of a Gas-Solid Chamber Experimentally and Numerically

Abstract

2 Abstract: In this research, gas velocity, initial static bed height and particle size effect on hydrodynamics of a non-reactive gas-solid fluidized bed chamber were studied experimentally and computationally. A multi fluid Eulerian model incorporating the kinetic theory for solid particles was applied to simulate the unsteady state behavior of this chamber and momentum exchange coefficients were calculated by using the Syamlal- O'Brien drag functions. Simulation results were compared with the experimental data in order to validate the CFD model. Pressure drops predicted by the simulations at different particle sizes and initial static bed height were in good agreement with experimental measurements at superficial gas velocity higher than the minimum fluidization velocity. Simulation results also indicated that small bubbles were produced at the bottom of the bed. These bubbles collided with each other as they moved upwards forming larger bubbles. Furthermore, this comparison showed that the model can predict hydrodynamic behavior of gas solid fluidized bed chambers reasonably well. Fluidized bed driers and chambers are used in a wide range of applications in various industrial operations, including chemical, mechanical, petroleum, mineral, and pharmaceutical industries. Understanding the hydrodynamics of fluidized bed chambers is essential for choosing the correct operating parameters for the appropriate fluidization regime (1-4). Computational fluid dynamics (CFD) offers an approach to understanding the complex phenomena that occur between the gas phase and the particles. The Eulerian-Lagrangian and Eulerian-Eulerian models have been applied to the CFD modeling of multiphase systems. For gas-solid flows modeling, usually, Eulerian- Lagrangian are called discrete particle models and Eulerian-Eulerian models are called granular flow models. Granular flow models (GFM) are continuum based and are more suitable for simulating large and complex industrial fluidized bed chambers containing billions of solid particles. These models, however, require information about solid phase rheology and particle-particle interaction laws. In principle, discrete particle models (DPM) can supply such information (5-8). DPMs in turn need closure laws to model fluid- particle interactions and particle-particle interaction parameters based on contact theory and material properties. In principle, it is possible to work our way upwards from direct solution of Navier-Stokes equations. Lattice-Boltzmann models and contact theory to obtain all the necessary closure laws and other parameters required for granular flow