Scale-up effects on flow patterns in the high shear mixing of cohesive powders

Cavinato, Mauro; Artoni, Riccardo; Bresciani, Massimo; Canu, Paolo; Santomaso, Andrea C.

doi:10.1016/j.ces.2013.07.037

Cited by 21 publications

(11 citation statements)

References 19 publications

(31 reference statements)

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“…In pharmaceutical product manufacturing, this type of mixer is used for the mixing of cohesive powders or more commonly for single-pot processing. [34][35][36] Because of the high-speed movement within the mixer-granulator which can fracture material easily and the problems associated with overmixing of lubricants, this type of mixer is usually not used for blending lubricants. 34 However, its use in this research is justified, as it was the intention to obtain an overlubricated blend.…”

Section: Effect Of the Paddle Speedsmentioning

confidence: 99%

Lubricant sensitivity in function of paddle movement in the forced feeder of a high-speed tablet press

Peeters

Vanhoorne

Remon

2016

Drug Development and Industrial Pharmacy

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To refer to or to cite this work, please use the citation to the published version: Peeters E., Vanhoorne V., Vervaet C., Remon J.P. AbstractContext: The negative impact of magnesium stearate on the hardness of tablets is a wellknown phenomenon, but the influence of paddle movement in the forced feeder on the lubricant effect during tablet compression is often neglected.Objective: The purpose of this research was to investigate the influence of paddle speed in the forced feeder on tablet tensile strength. Materials and methods:Mixtures of microcrystalline cellulose and magnesium stearate (0.5%)were blended using different methods (low & high shear). After blending, the formulations were compressed into tablets. All parameters of the tableting cycle were kept constant except the speed of the paddles in the forced feeder. Results and discussion:The blending technique affected the sensitivity of the formulation to the paddle speed. The tensile strength of pure microcrystalline cellulose tablets didn't change in function of paddle speed, while tablets prepared by low shear mixing became softer at higher paddle speed. The tensile strength of tablets manufactured using the high-shear mixed blend was low and didn't vary in function of paddle speed, suggesting that overlubrication already occurred during the initial blending step. Furthermore, analysis of the machine parameters allowed evaluation of the influence of the paddles on the flowability, initial packing and compactability of the powder mixtures. Conclusion:The results elucidated that during manufacturing of tablets using magnesium stearate-containing blends care should not only be taken during the blending step prior to tableting, but also during the tableting process itself, as paddle speed can affect tablet tensile strength, a critical quality attribute.

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Section: Effect Of the Paddle Speedsmentioning

confidence: 99%

Lubricant sensitivity in function of paddle movement in the forced feeder of a high-speed tablet press

Peeters

Vanhoorne

Remon

2016

Drug Development and Industrial Pharmacy

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“…Experiments monitoring the torque in high shear mixers therefore share some similiarity with the present case of the drag force applied by a wet granular system on a probe moving through it at constant velocity. The main difference however is the intensity of mixing, which is much larger in the high shear mixers, with significant centripetal accelerations of the wet material able to generate a toroidal flow pattern (Cavinato et al, 2013) not present in the our pan mixer.…”

Section: Introductionmentioning

confidence: 90%

Drag in wet granular materials

Artoni¹,

Loro²,

Richard³

et al. 2019

Powder Technology

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We have studied experimentally the effect of the water content on the drag force applied by a wet granular system on a probe moving through it at constant velocity. Similar to what has been observed for dry granular systems, the drag force is found to be independent of the velocity of the probe. By comparing our result with the dry case, we have shown that three main physical mechanisms occur: cohesion (consequence of capillary forces), contact lubrication and dilatancy induced by cohesion. The influence of the latter mechanism prevails in our system and the relative influence of the two former ones is found to depend on grains' characteristics. At important water contents, the granular system may become heterogeneous and its structure is modified by the motion of the probe. Our analysis is strengthened by shear cell experiments which also point out the importance of the geometry of the system on the effect of the water content.

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“…This was attributed to the effect of reduced friction between the particles and the bowl's wall. Cavinato et al (2013) used PIV techniques to measure powder surface velocities in a Mi-Pro fitted with the 1900 ml bowl and an impeller which did not feature the inclined side angles. As the scale and impeller blades were different to the Mi-Pro we used the results were not directly comparable although they were able to image the roping regime at higher impeller speed.…”

Section: Packing Densitiesmentioning

confidence: 99%

“…The code was then validated using high speed photography and used to simulate particle motion in a Mi-Pro lab scale granulator. These granulators are used to investigate granulation at a small scale (Gamble et al, 2009 andCavinato et al, 2013). They utilise an impeller with three blades inclined backwards at 45 degrees.…”

Section: Introductionmentioning

confidence: 99%

Development of a discrete element model with moving realistic geometry to simulate particle motion in a Mi-Pro granulator

Watson

Povey

Reynolds

et al. 2016

Computers & Chemical Engineering

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This paper presents the implementation of a methodology incorporating a 3D CAD geometry into a 3D Discrete Element Method (DEM) code; discussing some of the issues which were experienced. The 3D CAD model was discretised into a finite element mesh and the finite wall method was employed for contact detection between the elements and the spherical particles. The geometry was based on a lab scale Mi-Pro granulator. Simulations were performed to represent dry particle motion in this piece of equipment. The model was validated by high speed photography of the particle motion at the surface of the Mi-Pro's clear bowl walls. The results indicated that the particle motion was dominated by the high speed impeller and that a roping regime exists. The results from this work give a greater insight into the particle motion and can be used to understand the complex interactions which occur within this equipment.

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Scale-up effects on flow patterns in the high shear mixing of cohesive powders

Cited by 21 publications

References 19 publications

Lubricant sensitivity in function of paddle movement in the forced feeder of a high-speed tablet press

Lubricant sensitivity in function of paddle movement in the forced feeder of a high-speed tablet press

Drag in wet granular materials

Development of a discrete element model with moving realistic geometry to simulate particle motion in a Mi-Pro granulator

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