Numerical Analysis of Multiphase Solid-Gas Flow with Eulerian Models are Kinetic Theory Closure

Abstract

Multiphase solid-gas flows may be found in many industrial applications, from oil refining processes to hydrogen production reactors. In particular, we focus our interest in the dynamics of solid particles in a circulating fluidized bed riser of a Fluid Catalytic Cracking (FCC) unit, in which the solid particles distribution is one of the main variables in the global efficiency of the unit. In the last decades, much effort has been put in the development of Euler-Euler models with granular energy coupling to simulate this kind of problems due to the good balance between computational cost and accuracy of the numerical solution. In this work, in order to have a closure with the Navier-Stokes equations for the solid phase, we use the kinetic theory of granular flow with solid pressure and stress tensor models, while Wen-Yu and Ergun correlations are used to calculate the drag coefficients. All the numerical simulations are carried out with the fully unstructured open source code OpenFOAMR , based on the finite volume method. In addition, an iterative procedure based on a combination of PISO and SIMPLE method (called PIMPLE) is adopted and a proper discussion of its benefits is performed. To validate the solver, we present two widely studied multiphase flow problems. The first one consists on a sedimentation column starting from a uniform solid volume fraction suspension. The second one is based on a falling block of solid particles in a pure gas environment. Finally, we study a problem of a fluidized bed of particles with a constant gas injection from below. For this case, we are able to verify the good performance of the solver. In order to do this, we analyze the time and space average profiles of the solid volume fraction in comparison with the numerical and experimental results from several authors.