Particuology 8 (2010) 415–424 Contents lists available at ScienceDirect Particuology journal homepage: www.elsevier.com/locate/partic CFD modeling of a spouted bed with a porous draft tube Salar Azizi a,∗ , Seyyed Hossein Hosseini b , M. Moraveji a , Goodarz Ahmadi c a Chemical Engineering Department, Faculty of Engineering, Arak University, Sardasht, Arak 38156-875, Iran b Department of Chemical Engineering, Faculty of Engineering, Ilam University, Ilam, Iran c Department of Mechanical and Aeronautical Engineering, Clarkson University, Potsdam, NY 13699-5725, USA article info Article history: Received 26 February 2009 Received in revised form 30 August 2009 Accepted 16 December 2009 Keywords: Spouted bed Porous draft tube Hydrodynamics Kinetic theory CFD abstract Spouted bed with a porous draft tube is used for drying of grains and chemical products and thermal disinfestations process. This work provides a computational fluid dynamics (CFD) simulation of binary mixtures of glass particles in a spouted bed with a porous draft tube. The simulation used the multi-fluid Eulerian–Eulerian approach based on kinetic theory of granular flows, incorporating a kinetic-frictional constitutive model for dense assemblies of particulate solids and Gidaspow’s drag model for the inter- action between gas and particles. Influences of solids mass fraction and inlet gas flow rate on pressure distribution, gas and particle velocities were studied. The modeling results were compared with the exper- imental work of Ishikura, Nagashima, and Ide (2003) for the flow condition along the axis of the spouted bed. Good agreement between the modeling results and experimental data was observed. © 2010 Chinese Society of Particuology and Institute of Process Engineering, Chinese Academy of Sciences. Published by Elsevier B.V. All rights reserved. 1. Introduction Spouted beds, originally invented in Canada by Mathur and Gishler (1955) as an alternative to fluidized beds for handling coarse particles, are now widely applied in various physical opera- tions such as drying, coating, and granulation, as well as chemical reactors in coal gasification, catalytic partial oxidation, catalytic oxidative coupling reaction, catalytic polymerization, and pyroly- sis. The advantages of spouted beds for various chemical processes were reported by Mathur and Epstein (1974). Conventional spouted beds with simple structures are well known. According to Claflin and Fane (1983) the conventional spouted beds have a drawback, that is, the need for control of particle trajectory history, for otherwise the particles enter the spout area from the annulus from all levels, resulting essentially in random behavior of these particles. The insertion of an axially positioned non-porous draft tube into the conventional spouted bed has shown potential advantages in stability and flexibility of the system (Ishikura et al., 2003). There is, however, a potential lim- itation in using a spouted bed with a non-porous draft tube when the gas has an active role, such as drying or reaction, inasmuch as the non-porous draft tube prevents gas percolation from the draft tube into the annulus, thus reducing the net gas–solid con- tacting and therefore particle–gas mass and heat transfer in both ∗ Corresponding author. Tel.: +98 871 4173446–9. E-mail address: sa azizi@yahoo.com (S. Azizi). the spout and the annulus areas. Insertion of a porous draft tube, however, reduces this drawback, while still providing a means of controlling particle trajectory history (Ishikura et al., 2003). Com- paring spouted beds with porous and non-porous draft tube shows that the pressure drop and minimum spouting velocity for non- porous draft tube spouted beds are lower than spouted beds with porous draft tube. Increase in efficiency of heat and mass transfer is however the advantage of using a porous draft tube. Annulus gas flow rate and solids circulation rate are important factors from the viewpoint of gas–solids contact and in predicting the spouted bed performance with a draft tube. Hence, understand- ing the hydrodynamics of gas and particle flow is important for both industrial application and fundamental research. Most previous computational fluid dynamics (CFD) models for conventional spouted beds (Szafran & Kmiec, 2004) have provided important information on the flow field within the spouted beds for process design, scale up, optimization and reducing the need for experimentations. The present work uses the two-dimensional Eulerian two-fluid model (TFM) to study the hydrodynamic behav- ior of spouted beds with porous draft tube to give transient solutions under isothermal conditions. Modeling results are com- pared with the experiments of Ishikura et al. (2003) for spouted beds with porous draft tube. 2. Model equations Two methods have been improved for CFD modeling of gas–solid flows, the Eulerian–Lagrangian discrete element model 1674-2001/$ – see front matter © 2010 Chinese Society of Particuology and Institute of Process Engineering, Chinese Academy of Sciences. Published by Elsevier B.V. All rights reserved. doi:10.1016/j.partic.2009.12.004