(333f) Design Space Optimization of a Sachet Filling Device Using Discrete Element Method (DEM)

A pharmaceutical sachet filling device was modelled with the Discrete Element Method (DEM) using a cohesive contact model. The parameters for the contact model were calibrated by reproducing experimental flowability and compression data. The device comprises a horizontal screw feeder that periodically feeds a product hopper to keep the hold-up mass constant. A vertical auger draws the material from the product hopper into sachets at fixed doses, and a diamond-shaped agitator continuously mixes the material inside the product hopper. Various process parameters allow the independent control of the hold-up mass in the product hopper, the discharge rate of the material, and the mixing intensity in the product hopper. A DEM model was developed to optimize the design space, identify areas of risk in terms of powder segregation, and provide guidance for de-risking strategies. A special focus was placed on the impact of process parameters on mixing quality, particle velocities, and powder bed shape. The results indicate a high mixing quality across a wide range of operating parameters. The product hopper with the mixing agitator dampens the upstream concentration fluctuations—an effect that is investigated using a Residence Time Distribution (RTD) model. Less desirable operating points were identified by measuring the variability in mass and content at various locations within the device and in the sachets. Finally, a modification to one device part was suggested to improve the mass flow quality in the horizontal screw feeder section and further improve the overall mixing performance of the device.