Discrete element simulation of the hydrodynamics in a 3D spouted bed: Influence of tube configuration

• Hydrodynamics of a spouted bed is investigated using CFD-DEM coupling approach.
• Insertion of draft tube lowers the circular solid flux of the whole system.
• Larger entrainment distance leads to larger vertical solid flux in spout.
• Extension of tube above bed surface enhances solid axial velocity and flux in spout.
• The smallest erosion behavior appears in the lower part of draft tube.

The gas–solid flow in a 3D cylindrical spouted bed with a non-porous draft tube is investigated under the framework of CFD-DEM coupling approach. The gas motion is modeled by the k-ε turbulence model, and solid motion is modeled with discrete element method. Flow behavior of the fluid phase, the distribution properties of velocity, the concentration and flux of solid phase in the systems with different tube configurations are compared to evaluate the influence of tube geometry on the system performance. Besides, the erosion characteristic of the draft tube is discussed. Numerical results show that the insertion of draft tube significantly changes the gas–solid hydrodynamics. With the presence of draft tube, the velocity magnitudes of both fluid and solid phases in spout are enlarged significantly. The smaller the entrainment distance below the draft tube is, the larger fluid velocity appears in spout but a more dilute solid concentration in spout will be. Moreover, the extension of the draft tube above the bed surface enhances the solid motion in the central region of bed. Furthermore, the presence of draft tube lowers the solid circular flux of the whole system. For the system with draft tube, large entrainment distance and extension of draft tube above bed surface result in a large circular solid flux. The most severe erosion appears at the upper part of tube while the smallest erosion behavior appears in the lower part of tube. The smaller the entrainment distance is, the less erosion in the bottom of tube will be. Extension of tube above bed surface results in a larger erosion in the upper of the tube.

Instantaneous snapshots of particle distribution in slice Z = 0.105 m of spouted beds with different tube configurations under Ug = 37 m/s. (a)Hd = 0.07 m, Ld = 0.12 m; (b) Hd = 0.04 m, Ld = 0.15 m; (c) Hd = 0.07 m, Ld = 0.15 m. Figure optionsDownload as PowerPoint slide