The formation of solid bridges during agglomeration in a fluidized bed: Investigation by Raman spectroscopy and image analyses

Solid bridge formation in the agglomeration process is still not well-understood. This work has aimed to analyze particle class evolution, Raman spectra, and microscopy to comprehend granule formation in a fluidized bed throughout the process. Microcrystalline cellulose was agglomerated by maltodextrin solutions. The experimental statuses were classified in wet and dry conditions according to the combination of operating parameters. The effect of solution concentration (5.0, 20.0, and 35.0% w/w), solution flow rate (1.0 and 4.0 mL/min), and air temperature (30 and 90 °C) on particle size was checked. Afterward, the solution flow rate was increased from 1.0 to 4.0 mL/min while maintaining constant solution concentration and air temperature. Wet conditions led to more effective particle formation since the amount of liquid binder on the particle surface favored the formation of a sticky layer. The examination of data and images made it possible to identify the solid bridge formation and stability. [Display omitted] •Establishing and maintaining solid bridges is crucial to agglomeration success.•Raman spectroscopy identified the granule surface composition throughout the process.•Image analysis provided agglomeration visualization and solid bridge formation.•Data and images made it possible to delimit the stage of the solid bridge formation.