The Stokes Number Approach to Support Scale-Up and Technology Transfer of a Mixing Process

Willemsz, Tofan A; Hooijmaijers, Ricardo; Rubingh, Carina M.; Frijlink, Henderik W.; Vromans, Herman; Maarschalk, Kees van der Voort

doi:10.1208/s12249-012-9818-z

Cited by 4 publications

(3 citation statements)

References 14 publications

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“…Powder surface velocities observed by the camera (v p. ) at different fill volumes (φ) and container rotational speeds (ω) (experimental: white diamonds: φ040% (V/V), ω020 RPM; white squares: φ 040% (V/V), ω 030 RPM; white triangles: φ 040% (V/V), ω 0 40 RPM; X marks: φ053% (V/V), ω040 RPM; asterisks: φ067% (V/V), ω040 RPM; white circles: φ080% (V/V), ω040 RPM). Velocity of cascading layer obtained by DEM calculations: black circles: φ040% (V/V), ω0 40 RPM Our previous work showed that filler powder velocity is an important parameter in relation to the abrasion rate constant of agglomerates (8,19). For this reason, the following step is to evaluate effects of the speed of the cascading layer on the abrasion rate constants of agglomerates.…”

Section: Statistical Analysesmentioning

confidence: 99%

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

et al. 2012

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Abstract. Removal of microcrystalline cellulose agglomerates in a dry-mixing system (lactose, 100 M) predominantly occurs via abrasion. The agglomerate abrasion rate potential is estimated by the Stokes abrasion (St Abr ) number of the system. The St Abr number equals the ratio between the kinetic energy density of the moving powder bed and the work of fracture of the agglomerate. Basically, the St Abr number concept describes the blending condition of the dry-mixing system. The concept has been applied to investigate the relevance of process parameters on agglomerate abrasion in tumbling blenders. Here, process parameters such as blender rotational speed and relative fill volumes were investigated. In this study, the St Abr approach revealed a transition point between abrasion rate behaviors. Below this transition point, a blending condition exists where agglomerate abrasion is dominated by the kinetic energy density of the powder blend. Above this transition point, a blending condition exists where agglomerates show (undesirable) slow abrasion rates. In this situation, the blending condition is mainly determined by the high fill volume of the filler.

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Section: Statistical Analysesmentioning

confidence: 99%

“…These effects are correlated using the Stokes abrasion number (St Abr ). The Stokes abrasion number concept has been discussed earlier in more detail in previous papers (9,19):…”

Section: Powder Surface Velocity and Stokes Abrasion Number (St Abr )mentioning

confidence: 99%

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

et al. 2012

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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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