CFDEM® modelling of particle coating in a three-dimensional prismatic spouted bed

Particles which are difficult to handle in fluidized beds, such as big and non-spherical or small and co-/adhesive ones, can be fluidized in spouted beds. Nowadays, spouted bed processes are used for e.g. drying, spray granulation, encapsulation, and coating. Enhanced heat and mass transfer and intensive particle circulation allow a homogeneous distribution of the coating suspension on the particles accompanied by reduced agglomeration tendency. In the considered prismatic spouted bed the fluidization gas enters the bed chamber through two adjustable inlet slots. The coating suspension is sprayed via a two-fluid-nozzle in bottom-spray configuration (figure 1). The simulation of the spouted bed process was performed by means of the open source software CFDEM® coupling-PUBLIC, which combines the CFD-tool OpenFOAM® with the DEM-package LIGGGHTS® (1). The simulation results were visualized in ParaView (figure 2). Required input parameters for simulation, as e.g. the restitution coefficient, friction coefficient and Young’s modulus, were approximated with several experimental set-ups. Additionally, experiments were performed for validation of simulation results. Different turbulence models were investigated. Regarding the coating process, a spray zone was implemented in the simulations, whereby a self-written post-processing tool allowed the calculation of residence times of single particles in the spray zone. With this information a deterministic and physics-based simulation of the particle growth kinetics (growth rate) is possible. With regard to a feasible simulation time, the simulations were parallelized and a coarse-grain approach was used in order to handle a high amount of particles. Simulation results were in good agreement with experimental data. REFERENCES C. Goniva, C. Kloss, N.G. Deen, J.A.M. Kuipers and S. Pirker. Influence of Rolling Friction Modelling on Single Spout Fluidized Bed Simulations. Particuology, DOI 10.1016/j.partic.2012.05.002, 2012. Please click Additional Files below to see the full abstract

Segregation and mixing of granular material in industrial processes

Within the EU-funded PARDEM network mixing and segregation are studied in silos and heaps, agitated mixers and fluidized beds. A method is presented with which mixing and segregation can be characterized, adapted for quasi-static to dynamic systems and applied at the global system level as well as at the local level. This paper attempts to give an overview of the applicability of this analysis by providing three instances, being chute flow representing flow down a heap, agitated mixing and fluidization, in which the method is applied