Quantitative Characterization of Agglomerate Abrasion in a Tumbling Blender by Using the Stokes Number Approach

Willemsz, Tofan A; Nguyen, Tien Thanh; Hooijmaijers, Ricardo; Frijlink, Henderik W.; Vromans, Herman; Maarschalk, Kees van der Voort

doi:10.1208/s12249-012-9909-x

Cited by 3 publications

(3 citation statements)

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“…Breakage of agglomerates is governed by the balance (i.e., ratio) of the kinetic energy of the material (source for bond breakage) and the work needed to break the cohesive/adhesive bonds. The Stokes number and the ratio of the impact energy to the work done by the adhesive force, which essentially characterizes this balance, have been found to control agglomerate abrasion and breakage. Based on a similar idea, for the breakage of wet flexible agglomerates in the current study, the Weber number was used to characterize the ratio of the fiber kinetic energy compared to the work done to stretch a liquid bridge bond.…”

Section: Resultsmentioning

confidence: 99%

“…The modified Weber number is proportional to the square of impact velocity, and is inversely proportional to the liquid surface tension and the rupture distance. Previous work reports that the abrasion and breakage of agglomerates is characterized by the Stokes number of fracture, which is proportional to the square of impact velocity, v , and is inversely proportional to the square of the material yield strength, σ Y :

S_{t} = \frac{ρ_{b} v^{2} E}{σ_{Y}^{2}},

in which ρ b is the bulk density and E is the Young's modulus of the particles. Both the present modified Weber number and the previous Stokes number describe the ratio between the impact kinetic energy and the work of fracture of the agglomerate.…”

Section: Discussionmentioning

confidence: 99%

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Breakage of wet flexible fiber agglomerates impacting a plane

et al. 2019

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The breakage of an agglomerate of wet flexible fibers impacting a plane is computationally investigated in this work using the discrete element method. In the agglomerate, the fibers stick together due to cohesive liquid bridge forces. Agglomerate breakage with various impact conditions, initial configurations, fiber properties, and liquid bridge properties is systematically investigated. The degree of breakage is governed by the impact energy, the cohesion energy due to liquid bridges, the energy dissipation/absorption through fiber-fiber contacts and fiber deformation, and the efficiency of force transmission within the agglomerate. More specifically, breakage is promoted by increasing impact velocity, decreasing agglomerate size, increasing initial compaction, increasing fiber bending modulus, decreasing liquid surface tension, and decreasing liquid-to-solid volume ratio. Breakage is strongly dependent on the modified Weber number, that is, the ratio of the Weber number to a dimensionless rupture distance, which is a measure of the impact energy relative to the cohesion energy. K E Y W O R D Sagglomerate breakage, discrete element method, flexible fiber, liquid bridge force

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Section: Resultsmentioning

confidence: 99%

S_{t} = \frac{ρ_{b} v^{2} E}{σ_{Y}^{2}},

Section: Discussionmentioning

confidence: 99%

Breakage of wet flexible fiber agglomerates impacting a plane

et al. 2019

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“…The effects of the mixer rotation speed and the mixer size on abrasion were consistent with experiments . In addition, it was found that the Stoke number, defined as the ratio between the kinetic energy density of a powder bed and work of fracture of an agglomerate, was proportional to the abrasion rate, as observed in the experiments …”

Section: Introductionmentioning

confidence: 99%

DEM–PBM modeling of abrasion dominated ribbon breakage

Loreti

Reynolds

et al. 2017

AIChE Journal

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In dry granulation, fine cohesive powders are compacted into large multi‐particle entities, i.e., briquettes, flakes, or ribbons. The powder compaction is generally followed by milling, a size reduction process, which is crucial to obtain the desired granule size or properties. Abrasion and impact are two primary mechanisms of comminution in ribbon milling, but they are not completely understood. The aim of this article was hence to investigate numerically the fragmentation process induced by abrasion during ribbon milling. The discrete element method (DEM) was employed to simulate abrasion tests, for which three‐dimensional parallelepiped ribbons were generated using auto‐adhesive elastic spheres. The fragmentation rate, and the fragments size and number were determined for various surface energies and abrasive velocities. The DEM results showed that the mass‐equivalent fragment size distributions were bi‐modal, similar to the experimental observations and the numerical results for impact‐dominated ribbon milling reported in the literature. In addition, two quantities were determined from the DEM analysis, i.e., the number of large fragments and the fraction of fines, which was then integrated into the population balance models (PBM) so that a DEM–PBM multiscale modeling framework was developed to predict the granule size distribution during ribbon milling. The DEM–PBM results were compared with the experimental results reported in the literature, and a broad agreement was obtained, implying the proposed DEM–PBM can be used to analyse the ribbon milling behavior. © 2017 American Institute of Chemical Engineers AIChE J, 64: 1191–1204, 2018

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