A combination of density-based clustering method and DEM to numerically investigate the breakage of bonded pharmaceutical granules in the ball milling process--颗粒学报PARTICUOLOGY

Krok, A., Peciar, P., Coffey, K., Bryan, K., & Lenihan, S. (2021). A combination of density-based clustering method and DEM to numerically investigate the breakage of bonded pharmaceutical granules in the ball milling process. Particuology, 58, 153-168. https://doi.org/10.1016/j.partic.2021.03.008

A combination of density-based clustering method and DEM to numerically investigate the breakage of bonded pharmaceutical granules in the ball milling process

Alexander Krok ^a *, Peter Peciar ^d, Kieran Coffey^c, Keith Bryan ^b, Sandra Lenihan ^a

a Department of Process, Energy and Transport Engineering, Munster Technological University, Bishopstown, Cork T12 P928, Ireland
b Department of Mechanical, Biomedical and Manufacturing Engineering, Munster Technological University, Bishopstown, Cork T12 P928, Ireland
c Pfizer Newbridge, Littleconnell, Newbridge, Co. Kildare W12 HX57, Ireland
d Institute of Process Engineering, Faculty of Mechanical Engineering, Slovak University of Technology, Nam. Slobody 17, 81231 Bratislava, Slovakia

10.1016/j.partic.2021.03.008

Volume 58, October 2021, Pages 153-168

Received 20 October 2020, Revised 5 January 2021, Accepted 18 March 2021, Available online 3 April 2021, Version of Record 12 April 2021.

E-mail: alexander.krok@cit.ie

Highlights

• Ball milling of pharmaceutical granules was numerically investigated.

• The effect of milling speed on the fragmentation of DEM granules was examined.

• A discrete element model was developed to predict breakage of the granules.

• The clustering method was employed to identify the number and size of fragments.

Abstract

Ball milling is widely used in industry to mill particulate material. The primary purpose of this process is to attain an appropriate product size with the least possible energy consumption. The process is also extensively utilised in pharmaceuticals for the comminution of the excipients or drugs. Surprisingly, for ball mill, little is known concerning the mechanism of size reduction. Traditional prediction approaches are not deemed useful to provide significant insights into the operation or facilitate radical step changes in performance. Therefore, the discrete element method (DEM) as a computational modelling approach has been used in this paper. In previous research, DEM has been applied to simulate breaking behaviour through the impact energy of all ball collisions as the driving force for fracturing. However, the nature of pharmaceutical material fragmentation during ball milling is more complex. Suitable functional equations which link broken media and applied energy do not consider the collision of particulate media of different shapes or collisions of particulate media (such as granules) with balls and rotating mill drum. This could have a significant impact on fragmentation. Therefore, this paper aimed to investigate the fragmentation of bounded particles into DEM granules of different shape/size during the ball milling process. A systematic study was undertaken to explore the effect of milling speed on breakage behaviour. Also, in this study, a combination of a density-based clustering method and discrete element method was employed to numerically investigate the number and size of the fragments generated during the ball milling process over time. It was discovered that the collisions of the ball increased proportionally with rotation speed until reaching the critical rotation speed. Consequently, results illustrate that with an increase of rotation speed, the mill power increased correspondingly. The caratacting motion of mill material together with balls was identified as the most effective regime regarding the fragmentation, and fewer breakage events occurred for centrifugal motion. Higher quantities of the fines in each batch were produced with increased milling speed with less quantities of grain fragments. Moreover, the relationship between the number of produced fragment and milling speed at the end of the process exhibited a linear tendency.

Graphical abstract

Keywords

Ball milling; Granular pharmaceutical lactose; Density-based clustering; Discrete element method; Breakage; Mill rotation speed; ABAQUS

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