(130d) Discrete Element Modelling of Particle Transformations during Spheronisation

Spheronisation is a process whereby a short rod made of a wet powder mass is transformed into a dense spheroid. The process takes place in a spheroniser which is a fixed cylindrical vessel with vertical axis and a horizontally rotating base called friction plate. Under optimal processing conditions the particulate mass assumes the so-called â??ropingâ? regime. During the process the particles undergo a large number of impacts between each other and with the walls of the processing vessel. Each impact produces a small plastic deformation and rounding occurs as the cumulative effect of the impacts suffered by the particle. To date the process has been modelled using three strategies: Finite Element Analysis (FEA), whereby the deformation following each impact is followed explicitly; Multiple Impact Modelling of Particles (MIMP), which involves elasto-plastic contact laws; and Discrete Element Modelling (DEM). In this paper we extend DEM to model the evolution of the shape of each particle by using the algorithm employed by MIMP. This enables using impact conditions in the actual â??ropingâ? regime. The paper concludes with a spheronisation process map which identifies optimum material properties and process conditions for spheronisation.