Bench to batch: Linking pharmaceutical powder flow characterisation, intermediate bulk container discharge and video observations

Five well known excipients and a model drug substance with varied particle properties and bulk behaviour were chosen for the study. Based on the results APAP, NaCMC-XL, mannitol and DCPA were selected for a design to understand the impact of different blends. Two pilot scale unvented IBCs were used in the study. The IBC discharge rates were measured using a catch balance and the mode of flow and powder behaviour inside the IBC was recorded using a camera. The videos inside the IBC showed that regardless of flow mode, for powder to flow from the IBC an air burst was necessary. This was similar to observations when emptying water from a bottle. The extent of the air flow inside the IBC was strong and could possibly result in fluidisation segregation. The discharge curves of 15° and 30° hopper half angles were very similar, which was explained by the vertical air movement in the steeper hopper, which reduces the particle acceleration. Several good indicators of flow/no flow in the IBCs were found. However, for predicting the discharge rate there was a linear correlation between flow through an orifice and IBC discharge rate.

Powder flow from an intermediate bulk container - Discharge predictions and experimental evaluation

Powders are usually dispensed, blended, and transferred between different manufacturing steps in so-called Intermediate Bulk Containers (IBCs), and discharge from an IBC plays a critical role in the ability to manufacture high-quality tablets. To better understand IBC discharge, the flow behavior of selected excipients was comprehensively characterized using a number of techniques including the Hausner ratio/Carr's index, Erweka flow test, FlowPro flow test, shear test and wall friction test as well as FT4 powder rheometer experiments. Jenike's hopper design methodology was then used to predict the minimum non-arching outlet diameter and the mode of flow. Furthermore, the discharge rate from an IBC was predicted using a simple model that takes into account gravity and aerodynamic drag. The predictions were experimentally verified by measuring the discharge rate from a 20 L IBC using five commonly-used excipients. The small-scale Erweka flow test provided the best prediction of the full-scale IBC discharge experiment. Furthermore, a simple model that relied only on the particle size of the material and the diameter of the discharge opening was found to predict the IBC discharge rate remarkably well.