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

Abstract

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.

High-fidelity simulation of the 3-D full-loop gas–solid flow characteristics in the circulating fluidized bed

“…The LES-DEM coupling approach proposed in the current work has been validated with the experimental work of Müller et al (2008) in our previous work Luo et al, 2013aLuo et al, , 2013b). In the model validation, the minimum fluidizing velocity obtained in the experiment has been accurately obtained.…”

“…The investigated hydrodynamics at two different heights of the system agree well with the experimental data both qualitatively and quantitatively. More details related to the model validation can be found in our previous work Luo et al, 2013aLuo et al, , 2013b. Based on the validation, the coupling model has been applied to investigate the internal transportation mechanisms of solid phase and the tube erosion in the internally circulating fluidized bed Luo et al, 2013aLuo et al, , 2013bYang et al, 2014aYang et al, , 2014b, in which the internal circulation of solid phase is established by introducing a vertical draft tube or a centrally assigned baffle plate in the bubbling fluidized bed.…”

“…More details related to the model validation can be found in our previous work Luo et al, 2013aLuo et al, , 2013b. Based on the validation, the coupling model has been applied to investigate the internal transportation mechanisms of solid phase and the tube erosion in the internally circulating fluidized bed Luo et al, 2013aLuo et al, , 2013bYang et al, 2014aYang et al, , 2014b, in which the internal circulation of solid phase is established by introducing a vertical draft tube or a centrally assigned baffle plate in the bubbling fluidized bed. Besides, the solid mixing in the bubbling fluidized bed (Gui and Fan, 2011) and the hydrodynamics in the fluidized bed with tube bundle (Gui et al, 2008;Gui and Fan, 2009) have been explored.…”

Modelling of Spouted and Spout-Fluid Beds: Key for Their Successful Scale Up

“…In this sense, spout-fluid beds are more abundant in DEM simulations compared with those performed with TFM, as it can be seen in Table 1 and Section 3.2. A group of researchers from the Zhejiang University employed a geometry with a zig zag wall instead of an inclined one in two different works [103,104] to reproduce the experiments performed in a spouted bed with a conical base by Vieira Neto et al [143].…”

“…The circulation of solids within a spouted bed with and without a draft tube was investigated by Luo and colleagues [104] who highlighted the substantial differences observed: the solids dispersion took place in different zones, being more intense when the draft tube is used. They also showed that the extension of the draft tube over the bed surface makes the solid circulation more vigorous.…”