Effect of high stirring speed on the agglomerate behaviors for cohesive SiO2 powders in gas fluidization--颗粒学报PARTICUOLOGY

Fu, L., Zhou, S., Zheng, Y., & Zhuang, L. (2023). Characterizing dynamic load propagation in cohesionless granular packing using force chain. Particuology, 81, 135-148. https://doi.org/10.1016/j.partic.2023.01.007

Effect of high stirring speed on the agglomerate behaviors for cohesive SiO₂ powders in gas fluidization

Fan Liu ^{a b}, Zhan Du ^b *, Qingshan Zhu ^{a b *}, Xiaojun Guo ^{a b}, Hebang Shi ^{a b}, Pengpeng Lv ^b, Hongzhong Li ^b

a School of Chemical Engineering, University of Chinese Academy of Sciences, Beijing, 100049, China
b State Key Laboratory of Multiphase Complex Systems, Institute of Process Engineering, China Academy of Sciences, Beijing, 100190, China

10.1016/j.partic.2022.12.007

Volume 80, September 2023, Pages 192-201

Received 5 September 2022, Revised 4 December 2022, Accepted 14 December 2022, Available online 22 December 2022, Version of Record 1 March 2023.

E-mail: zdu@ipe.ac.cn; qszhu@ipe.ac.cn

Highlights

• A high-speed stirring fluidized bed is designed to improve the fluidization of cohesive powders.

• The powders are well dispersed in the regime of agglomerate particulate fluidization.

• Transitions of different fluidization regimes are depicted comprehensively.

• The stirring applied enlarges the operational range of agglomerate particulate fluidization.

• The agglomerate sizes tend to the original particle size with high stirring speed.

Abstract

The effects of superficial gas velocity and mechanical stirring speed on the precise regulation of flow regimes for cohesive SiO₂ powders (mean diameter is 16 μm) were experimentally investigated in a stirring-assisted fluidized bed. The results showed that compared with the agglomerates formed in the non-assisted fluidization of cohesive SiO₂ powders, the introduction of mechanical stirring could effectively reduce the size of agglomerates and well disperse the agglomerates during fluidization. The best regulation range of agglomerate particulate fluidization can be achieved at 600 rpm when agglomerate sizes were reduced to below 200 μm. Further investigation based on the operational phase diagram revealed that transformations of flow regimes were dominated by both stirring speed and gas velocity. The stirring applied enlarges the operational range of agglomerate particulate fluidization (APF) with a delayed onset of bubbling for cohesive particles. However, the exorbitant speed increases the collision velocity and contact area between small agglomerates, which results in the formation of unstable agglomerates and the whirlpool of powder.

Graphical abstract

Keywords

Cohesive powders; Stirring-assisted fluidized bed; Agglomerate size; Agglomerate particulate fluidization

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