Particle Dispersion and Circulation Patterns in a 3D Spouted Bed with or without Draft Tube

Solid dispersion and circulation properties in a 3D spouted bed with or without a draft tube are reported based on the CFD-DEM coupling approach. The distribution characteristics of the local and global solid dispersion coefficients are studied. Meanwhile, the effects of tube configuration and bed diameter on these two aspects are investigated. The results show that the large lateral dispersion coefficient concentrates in the spout annulus interface and the lower part of the fountain region, while the vertical one lies in the central region of the spout. Insertion of a draft tube results in not only large systematic vertical and lateral dispersion coefficients but also more regular particle circulation patterns in the lateral and vertical directions. Furthermore, the larger the entrainment distance of the draft tube, the higher the local and systematic dispersion coefficients are and also an increasing particle circulation rate appears. Extension of the draft tube above the bed surface leads to a larger particle circulation rate and more vigorous dispersion system. With the scale-up of apparatus, both the lateral and the vertical dispersion coefficients are enhanced and solid circulation becomes more energetic.