Influence of cycle time distribution on coating uniformity of particles in a spray fluidized bed by using CFD-DEM simulations--颗粒学报PARTICUOLOGY

Li, H., Liu, D., Ma, J., & Chen, X. (2023). Influence of cycle time distribution on coating uniformity of particles in a spray fluidized bed by using CFD-DEM simulations. Particuology, 76, 151-164. https://doi.org/10.1016/j.partic.2022.08.010

Influence of cycle time distribution on coating uniformity of particles in a spray fluidized bed by using CFD-DEM simulations

Heng Li, Daoyin Liu ^*, Jiliang Ma, Xiaoping Chen

Key Laboratory of Energy Thermal Conversion and Control of Ministry of Education, School of Energy & Environment, Southeast University, Nanjing, 210096, China

10.1016/j.partic.2022.08.010

Volume 76, May 2023, Pages 151-164

Received 31 May 2022, Revised 26 July 2022, Accepted 8 August 2022, Available online 29 August 2022, Version of Record 2 November 2022.

E-mail: dyliu@seu.edu.cn

Highlights

• A spray fluidized bed of coating process is simulated by a CFD-DEM model.

• Cycle time distribution of particles becomes narrower by optimizing bed structure.

• Coating uniformity is improved as cycle time distribution becomes narrower.

• Properly increasing gas velocity and temperature the coating uniformity increases.

• Properly reducing liquid spray rate the coating uniformity increases.

Abstract

Cycle Time Distribution (CTD) plays a critical role for determining uniformity of particle coating in spray fluidized beds. However, the CTD is influenced by both geometrical structure and operating conditions of fluidized bed. In this study, a spray fluidized bed of coating process is simulated by a comprehensive Computational Fluid Dynamics-Discrete Element Model (CFD-DEM). To achieve different behaviors of CTD, some modifications are designed on a pseudo-2D internally circulating fluidized bed, which traditionally composes of a high-velocity upward bed and low-velocity downward bed. These modifications include making the air distributor slope and/or laying a baffle in the downward bed. First, the CTD and evolution of particle size distribution under different bed structures are compared. The CTD directly influences the coating uniformity. By making the particles flowing along a parallel direction in the downward bed through the geometrical modifications, the CTD becomes narrower and the coating uniformity is significantly improved. Second, under the optimized bed structure, the influence of operating conditions on the coating uniformity is studied. Properly increasing the fluidization gas velocity and the fluidization gas temperature and reducing the liquid spray rate can improve the coating uniformity.

Graphical abstract

Keywords

Spray fluidized bed; Particle coating; Cycle time distribution; CFD-DEM

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