(130g) Novel Dispensing Mechanism to Achieve Continuous Flow of Highly Cohesive Powders

Under the best of circumstances, powder flow is difficult to control. Powders can bridge in hoppers, rat hole, avalanche, segregate, and adhere to surfaces through electrostatic or other interactions. Cohesive powders are especially challenging, and a significant body of research spanning many decades has been devoted to their study. These flow challenges are amplified in continuous pharmaceutical manufacturing processes where powders must not only be fed reliably, but also at precisely controlled feed rates. In these cases, feed screws are typically employed to meter powders at a desired mass flow rate. While the screw feeder design provides excellent results for many powders, they can fail to provide adequate results when feeding very low levels (mass flow rates) of cohesive powders or powders with very low bulk density. These low-level ingredients may include lubricants such as sodium stearyl fumarate and magnesium stearate, glidants such as silica, or various active pharmaceutical ingredients which are often milled to mean particle sizes below 20 microns. In this work, a novel continuous dispensing mechanism was explored to achieve continuous feeding of pharmaceutical powders. Initial results suggest that powders can be fed as low as 1/10^th of the mass flow rate and with improved precision compared to twin feed screws.