Wurster fluidised-bed coating: Coarse-graining technique within CFD-DEM in conjunction with heat and mass transfer

• Published in: Powder technology Vol. 443; p. 119901
• Main Authors: Kjaer Jepsen, Philip, De Juan, Luis Martin, Boje, Astrid, Sarangi, Sohan, von Corswant, Christian, Sasic, Srdjan
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.07.2024
• Subjects: CFD-DEM; Coarse-graining technique; Granular flow regime characterisation; Liquid spray modelling; Three-phase system; Wurster fluidised-bed coater; CFD-DEM; Coarse-graining technique; Wurster fluidised-bed coater; Granular flow regime characterisation; Liquid spray modelling; Three-phase system
• ISSN: 0032-5910; 1873-328X
• DOI: 10.1016/j.powtec.2024.119901

In this study, we use a combined CFD-Discrete Element Method to assess predictive capabilities and numerical implications of a coarse-graining technique in Wurster fluidised-bed coaters. We investigated both hydrodynamics and heat and mass transfer and conducted simulations of a full three-phase system for the original and three coarse-grained systems, analysing velocity distributions, macroscopic solid stresses, moisture content and phase temperatures. We achieved a logarithmic simulation speed-up by aggregating up to 64 original particles into each coarse grain. This was accomplished while maintaining fidelity to the original CFD-DEM system in terms of reproducing with high accuracy macroscopic granular flow properties in different regions of a coater (drying, tube and bed regions). By integrating a liquid spray and humid air, we demonstrated that the phase temperatures were accurately predicted within the coarse-grained system, with a high capability of delivering liquid spray distributions with the same uniformity and drying. We also give arguments for choosing a certain degree of coarse-graining as a compromise between a desired reduction of computational costs and a trustworthy reproduction of granular-flow physics encountered in different regions of a Wurster bed. Our findings pave the way to using CFD-DEM to industrially-scaled Wurster-bed systems, which is currently unfeasible due to prohibitive computational costs. [Display omitted] •Logarithmic simulation speed-up in CFD-DEM via coarse-graining (particle scaling).•Modelling of solid, gas, and liquid phases in the Wurster fluidised-bed coating process.•Evaluation of granular flow rheology, with analysis of inter-phase momentum, heat, and mass transfer.•Experimental validation of CFD-DEM predictions with PEPT data.