Optimizing the design of eccentric feed hoppers for tablet presses using DEM

The discharge performance in eccentrically shaped, conical hoppers is investigated using the discrete element method (DEM). While powder discharge from hoppers has been well studied, most work has focused on axisymmetric, conical hoppers and plane flow, wedge-shaped hoppers. Yet, pharmaceutical tablet presses often use eccentric hopper designs that do not fall into either of these categories. The flow performance in these hoppers is compared to that in concentrically shaped, conical hoppers. Results show the discharge rate is up to 35% greater for eccentric hoppers and shows good agreement with a modified Beverloo correlation. The flow mode during discharge (mass-flow/funnel-flow) is similar for each hopper shape. Finally, the extent of segregation over time is comparable but a significant composition gradient exists across the outlet of eccentric hoppers. This has implications for processes where the discharge from an eccentric hopper is split downstream, such as the bifurcation of the powder feed to a double-sided tablet press.