Powder agglomeration in continuous powder feeding by twin-screw feeder

The presence of powder agglomerates results in product with poor content uniformity and intermittent high potency in the processing of pharmaceutical powders. We developed a novel and easy-to-implement methodology, applying image analysis, to quantify the size of powder agglomerates when a powder passes through a screw feeder. Subsequently, agglomeration tendencies of twenty-one pharmaceutical powders were examined and classified. Notably, both the size and endurance of agglomerates were quantified, and our study revealed that the agglomeration tendency of powders can be explained by particle size and compressibility: Powders with small particle size (D50 < 30 μm), and large compressibility (> 35% at 15 kPa normal stress) tend to form large and enduring agglomerates, which can be difficult to eliminate in downstream processes. The study also illustrates how two materials, one that produces enduring and the other unenduring agglomerates, display substantially different content uniformity in the final product after being processed semi-continuously.