Numerical Investigation of the Mixing of Non-spherical Particles in Fluidized Beds and during Pneumatic Conveying

Abstract

Fluidized beds as well as pneumatic conveying are of high relevance to many processes in chemical engineering and energy technology. A possible framework to describe these systems is to use a combined Computational Fluid Dynamics (CFD) - Discrete Element Method (DEM) approach. All particles in the system are addressed by solving the Newtonian and Eulerian equations of motion. The fluid flow is resolved through the Navier-Stokes equations using the finite-volume method. In recent years, simulations focused mainly on spherical particles, although real bulk solids consist of complex shaped particles. For these particles, contrary to spheres, an important factor that plays a fundamental role in describing their principal behavior is the orientation which can be accurately expressed by a number of rotation parameters. So far only few CFD-DEM studies have been performed in order to investigate particle-fluid systems of complex shaped particles. Especially mixing is not well understood for non-spherical particles in the context of a CFD-DEM coupling.We performed CFD-DEM simulations of a model type fluidized bed as well as of a pipe bend being part of a pneumatic conveying system in order to investigate the influence of particle shape on mixing. Results indicate that mixing is strongly influenced. Hence, the coupled CFD-DEM framework using complex shaped particles captures the system behavior more detailed than by using spheres and gives a better understanding of mixing phenomena.