DEM–CFD modeling of flows and breakages of small agglomerates in fluid

In processing industries, it is often important to know whether agglomerates and granules during fluidization break into fragments or remain intact and whether they increase or decrease in size. The objective of this study is to investigate agglomerate behaviors during fluidization using an “in-house” computational fluid dynamics (CFD)–discrete element method (DEM) simulation software. Particle agglomerates, formed using a cohesive contact model, are introduced into a fluidized bed, where they flow and collide with other particles and agglomerates. The mass centers of the agglomerates are traced, together with their porosities and internal coordination numbers. The results show that agglomerates can significantly affect the fluid field. Breakage behaviors are observed and quantified under different gas injection velocities and agglomerate strengths. Statistical analysis across all 36 agglomerates reveals that breakage probability increases from 8% at 0.5 m/s to 72% at 1.5 m/s for γ = 0.5 J/m2, and from 22% to 89% for γ = 0.2 J/m2. Mean breakage times range from 28.7 ± 14.1 ms to 61.8 ± 8.4 ms depending on conditions. The fragment size distribution exhibits two distinct regimes (large fragments and small debris), and the exponent for the debris is found to be independent of gas velocity and bond strength within the studied range (α = 2.39 ± 0.08). Comparison with recent CFD–DEM studies confirms that our findings on velocity-dependent breakage are consistent with the literature, while our detailed statistical analysis of agglomerate internal structure provides new insights. The present simulations suggest that this approach can serve as a predictive tool for agglomerate behavior in fluidized beds.