Fine-tuning particle coatings: A comparative study of liquid atomization methods in fluidized bed processes (Open Access)--颗粒学报PARTICUOLOGY

a Thermal Process Engineering, Otto von Guericke University, Universitätsplatz 2, 39106, Magdeburg, Germany
b Mechanical and Aerospace Engineering, Princeton University, Princeton, NJ, 08544, USA
c Mechanical Engineering, Shamoon College of Engineering, Beer Sheva, 84100, Israel

10.1016/j.partic.2026.05.008

Volume 115, August 2026, Pages 91-105

Received 17 July 2025, Revised 27 April 2026, Accepted 12 May 2026, Available online 21 May 2026, Version of Record 27 May 2026.

E-mail: serap.akbas@ovgu.de

Highlights

• A newly developed three-channel coaxial nozzle was applied in fluidized bed particle coating.

• The new nozzle generates droplets ∼10 μm, bridging the gap between aerosol generators and conventional nozzles.

• Non-porous glass and porous γ-Al₂O₃ particles were coated using an aqueous sodium benzoate solution.

• Process yield, coating coverage, coating thickness, and surface roughness were evaluated.

• The new nozzle shows strong potential as an alternative to conventional nozzles by producing finer droplets.

Abstract

This study compares the performance of a new three-channel coaxial nozzle with a conventional Schlick nozzle in fluidized bed particle coating. The new nozzle produces droplets with a Sauter mean diameter of around 10 μm, offering a middle ground between aerosol and conventional nozzles. Yields of processes, coating coverages of particles, coating thickness and surface roughness were compared for the same experimental conditions of these nozzles. Non-porous glass particles (mean diameter 653 μm) and porous γ-Al₂O₃ particles (mean diameter 610 μm) were used as cores, with an aqueous sodium benzoate (NaB) solution as the coating liquid. A scanning electron microscope (SEM) was utilized to capture images of the particles after each experiment. To analyze the coverage on the particle surfaces, MATLAB image processing was applied to SEM images of coated particles. Moreover, these images were used to determine the surface roughness of the coating. In addition to manual measurements of coating thickness on particles by image processing, some coated γ-Al₂O₃ particles were sectioned to measure the coating thickness by ImageJ. The manual thickness measurements were supplemented by results obtained by laser scattering. The coating process by means of the new nozzle was also compared with an aerosol coating process which has droplet size with a mean diameter of around 1 μm, in terms of process yield, product coating coverage and thickness. The new nozzle acts as an intermediate between the aerosol generator and the conventional Schlick nozzle in terms of droplet size. These findings suggest that the new nozzle has significant potential for use in fluidized particle coating, as an alternative to conventional nozzle, offering smaller droplet size.

Graphical abstract

Keywords

Fluidized bed; Coating particles; Atomization; Process yield; Coverage; Layer thickness; Coating surface roughness

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