Effect of fluidized bed particle properties and agglomerate shape on the stability of agglomerates in a fluidized bed

In particulate operations, agglomeration is a vital process as it is inevitable in the pharmaceutical, food, and detergent industries. It can be used to create particles of specific shapes and sizes, stabilize particulate mixtures and reduce dust emissions. However, agglomeration increases reactor fouling in fluid coking systems. The goal of this study is to understand the effect of fluidized bed particles and agglomerate shape on agglomerate stability, i.e. the resistance of agglomerates to breakage. Artificial agglomerates were made of polyurethane foam, magnets and radio frequency identification (RFID) tags. Artificial agglomerates greatly improve the reproducibility and ease of the agglomerate stability measurements, and agglomerate breakage anywhere in the bed is detected with an RFID reader. The important findings for the effect of bed particles on the stability of agglomerates are that at low excess fluidization velocities, if the density of the bed particles is increased, the agglomerates spend more time in the surface region of bed, where bubbles are larger. At high velocity, the effect is negligible. An empirical correlation is developed to predict the agglomeration breakage time. The bed particle size and shape have a negligible effect on the agglomerate stability. Spherical agglomerates are more stable than cylindrical agglomerate as these agglomerates are exposed to less shear from bed turbulence.

Correlation for the half-life of wet agglomerates in a fluidized bed:t50−1=a+blnuumf2+cρaggloρmf0.5+dρaggloρmf.Figure optionsDownload as PowerPoint slideHighlights
► Wet agglomerate stability depends on fluidized bed particles.
► Bed particle size and shape of a negligible effect on stability
► Larger bed particle density promotes agglomerate breakage.
► Spherical agglomerates are more stable than cylindrical agglomerates.