Coarse-graining dense discrete phase model for modeling particle dynamics in a 3D tapered fluidized bed coater: Analysis of different drag models

Abstract

Fluidized bed coating (FBC) is widely employed in the food industry to microencapsulate food powder ingredients, primarily using a top-spray design in a tapered fluidized bed (TFB). A comprehensive understanding of particle dynamics is crucial for successfully designing FBC processes. This study focuses on developing and analyzing the coarse-graining dense discrete phase model (CG-DDPM) to investigate particle fluid dynamics in tapered fluidized bed coater (TFBC). Following the successful development of the CG-DDPM, we conducted a sensitivity analysis of drag force models due to the unique operating conditions involved. Five drag models were investigated, including four classic homogeneous drag models (Gidaspow, Wen-Yu, Syamlal-O'Brien, and Huilin-Gidaspow) and one advanced energy-minimization-multiscale bubbling (EMMS-B) heterogeneous model. While all drag models exhibited reasonable qualitative behavior, the EMMS-B model demonstrated superior quantitative performance, particularly at a gas velocity (Ug) of 1.75 m/s. However, at Ug = 1 m/s, none of the drag models perfectly resolved the axial and lateral solids concentration profiles. This study's findings contribute to identifying the best-performing drag model and highlight the need for more appropriate drag models to represent particle fluid dynamics in TFBC accurately. Moreover, employing the EMMS-B model in the top-spray design of TFBC can enhance the microencapsulation of food powder ingredients due to its superior particle dynamics predictions compared to homogeneous drag models.