A comparative study on the influence of the gas flow rate on the hydrodynamics of a gas-solid spouted fluidized bed using Euler-Euler and Euler-Lagrange / DEM models Naser Almohammed a,∗ , Falah Alobaid b , Michael Breuer a , Bernd Epple b a Professur f¨ ur Str¨ omungsmechanik, Helmut-Schmidt-Universit¨ at Hamburg, Holstenhofweg 85, D-22043 Hamburg, Germany b Institut f ¨ ur Energiesysteme und Energietechnik, Technische Universit¨ at Darmstadt, Otto-Berndt-Straße 2, D-64287 Darmstadt, Germany Abstract In this work, different modeling approaches are used to study the hydrodynamics of gas-solid flows in a three-dimensional, lab-scale spouted fluidized bed. In particular, the simulation results obtained by the two-fluid model are compared with those of coupled CFD/DEM simulations. To explore the effects of the gas mass flow rate on the ability of the used simulation techniques to predict the flow behavior in the simulated test case, two different fluidization conditions are considered while maintaining the same computational set-up. The spouted fluidized bed has been evaluated by means of high-speed imaging for validating the simulation results. A comparative study of the two modeling approaches with experimental observations for bubble size in terms of the representative bubble diameter and the bed height has been carried out under both operating conditions. To identify significant simulation settings for the two-fluid model, a parameter study is carried out. The investigated input parameters include the gas-particle drag models, the granular tem- perature approach, the solid-phase wall boundary conditions in terms of specularity coefficient and the particle-particle restitution coefficient. At a gas mass flow rate of 0.005 kg/s, the predicted characteristics of the bubble formation and the bed expansion using both techniques are in very good agreement with experimental observations. Using the same validated settings, the two-fluid model shows some notable discrepancies when the gas mass flow rate is increased to 0.006 kg/s, while the DEM is more successful than the two-fluid model in reproducing realistic flow patterns. Although both techniques predict the right fluidization regimes and trends in bubble sizes and bed expansion, their results deviate significantly from the experimental data during the final stage of the bubble formation. The most important reasons for the differences in predicting the bed dynamics along with the advantages and limitations of the two approaches are discussed. Keywords: Spouted Fluidized Bed, Euler-Euler Model, Euler-Lagrange Model, Two-Fluid Model, Discrete Element Method 1. Introduction A gas-solid fluidized bed is typically a packed bed of particulate solids in a container with perforated base, through which an upward flow of gas is passed. Fluidized bed reactors have been widely applied to various industrial processes including the coating, the granulation, the combustion and the gasification of coal, biomass and solid waste. Here, the corresponding multiphase flows, which are of substantial interest in the recent academic and industrial research, play a significant role. The modeling, the characterization and the advanced understanding of the hydrodynamics of these complex flows are still challenging because their behavior is still unknown and difficult to be predicted in many applica- tions. Therefore, the basic objective of modeling the hydrodynamics of the particulate flow behavior in a fluidized bed is to obtain a realistic flow structure. Experiments have provided substantial insights into the hydrodynamic behavior of particulate flows in lab-scale fluidized beds, but they are difficult, expensive, and limited to this scale of fluidized beds. ∗ Corresponding author. Tel.: +49 40 65412291; Fax: +49 40 65413781 Email address: naser.almohammed@hsu-hh.de (Naser Almohammed) Powder Technology 264 (2014) 343–364