Ultrathin coating of fluidized particles by means of aerosol
Final Report Abstract
The primary objective of this project was to conduct an in-depth investigation of a novel and promising particle coating technique utilizing aerosol droplets. To achieve this, fluidized bed coating experiments were carried out under varying process conditions using aerosol droplets with a mean diameter of approximately 1 μm. These experiments aimed to assess the impact of process parameters on key quality attributes such as process yield, coating coverage, and layer thickness. The core materials used in the study were glass and porous γ-Al₂O₃, with mean diameters of 653 μm and 610 μm, respectively. As coating liquids, sodium benzoate (NaB) solution and silicon dioxide (SiO₂) nanosuspension were employed. Following sample collection, scanning electron microscopy (SEM) images of the coated particles were captured and analyzed using MATLAB image processing to evaluate coating coverage while accounting for curvature effects. The obtained coverage data was compared with results from Monte Carlo (MC) simulations. A significant discrepancy was observed due to island growth on the particle surfaces, which can be attributed to the preferential deposition of droplets on pre-coated areas. To improve the accuracy of the coating process simulation, the MC model was modified to incorporate a preferential deposition factor for each experiment. Additionally, some coated particles were cross-sectioned to measure the layer thickness. The intraparticle coating thickness distribution predicted by the MC simulations was found to be in reasonable agreement with the experimentally measured thickness. The findings indicate that process yield, coating coverage, and the preferential deposition factor are influenced by several experimental parameters, including expanded bed height, fluidization air temperature, atomization pressure, the number of aerosol inlets, and the surface potential of the core particles. Moreover, this study was the first to examine the effect of surface charge on droplet deposition for different core materials, an aspect that was not originally included in the project proposal. In particular, experiments with SiO₂ nanosuspension demonstrated that γ-Al₂O₃ cores could be uniformly coated with SiO₂ nanoparticles, achieving a layer thickness of approximately 1.1 μm. This highlights the potential of aerosol droplet deposition as an innovative semi-wet approach for nanoparticle coating of large particles without the use of binders. Furthermore, a continuum process yield model was developed. Computational fluid dynamics (CFD) simulations were conducted to identify the spray zone within the fluidized bed, enabling the determination of the effective bed height required for yield predictions under different experimental conditions. In future research, integrating this continuum yield model with Monte Carlo deposition simulations may allow for the fully predictive simulation of the coating process, facilitating process optimization and scale up.
Link to the final report
http://dx.doi.org/10.25673/121660
Publications
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Finetuning particle coatings: A comparative study of liquid atomization methods in fluidized bed processes
Akbas, S.; Mezhericher, M.; Hoffmann, T.; Razorenov. N.; Pan. Z. & Tsotsas, E.
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Ultrathin coating of fluidized particles by means of aerosol. Poster Presentation Jahrestreffen 2022 der DECHEMA-Fachgruppen Lebensmittelverfahrenstechnik (LVT) und Trocknungstechnik (TRO). Frankfurt am Main, Germany, 10- 11 March 2022
Akbas, S.; Hoffmann, T. & Tsotsas, E.
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Investigation of Island Growth on Fluidized Particles Coated by Means of Aerosol. Processes, 11(1), 165.
Akbas, Serap; Chen, Kaicheng; Hoffmann, Torsten; Scheffler, Franziska & Tsotsas, Evangelos
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Investigation of island growth on particles coated by means of aerosol. In: Proceedings of the 10th International Granulation Workshop. Sheffield, UK, 21-23 June 2023
Akbas, S.; Hoffmann, T.; Chen, K.; Scheffler, F. & Tsotsas, E.
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Investigation of island growth on particles coated by means of aerosol. Poster Presentation Jahrestreffen 2023 der DECHEMA-Fachgruppen Abfallbehandlung und Wertstoffrückgewinnung (AuW) und Trocknungstechnik (TRO). Dresden, Germany, 6-7 March 2023
Akbas, S.; Hoffmann, T.; Chen, K.; Scheffler, F. & Tsotsas, E.
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Ultrathin particle coating in fluidized bed by using aerosols. Poster Presentation International Congress on Particle Technology (PARTEC). Nuremberg, Germany, 26-28 September 2023
Akbas, S.; Hoffmann, T. & Tsotsas, E.
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Aerosol fluidized bed coating: Exploring the impact of process conditions on process yield, coating coverage and thickness. Chemical Engineering Journal, 495, 153349.
Akbas, Serap; Zhang, Jinchi; Hoffmann, Torsten & Tsotsas, Evangelos
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Exploring the impact of process conditions on aerosol coating quality and coverage. Oral Presentation Jahrestreffen 2024 der DECHEMA- Fachgruppen Wärme- und Stoffübertragung (WSUE) und Trocknungstechnik (TRO). Magdeburg, Germany, 11-13 March, 2024
Akbas, S.; Hoffmann, T. & Tsotsas, E.
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Ultrathin aerosol coating process for fluidized particles. In: Proceedings of the 23rd International Drying Symposium (IDS2024). Wuxi, Jiangsu Province, China, 22-25 November, 2024
Akbas, S.; Hoffmann, T. & Tsotsas, E.
