Continuous Drying of Small Particles for Pharmaceutical Applications—An Evaluation of Selected Lab-Scale Systems

Moving toward continuous manufacturing in the pharmaceutical industry offers new possibilities, such as reducing costs and improving flexibility and product quality. However, this paradigm change requires new small-scale continuous manufacturing technologies. Since drying is one of the crucial elements of pharmaceutical production, we performed an evaluation of existing drying technologies suitable for continuous production. We focused on small-scale equipment for handling preconcentrated slurries at the kg/h scale. Lactose (soluble) and ibuprofen (poorly soluble) suspensions were dried, first, in two fluidized bed spray dryers, second, in a small-scale spray dryer, third, in a spin flash dryer, fourth, in a paddle dryer, and, finally, in a corotating twin-screw extruder. During these trials we evaluated the performance of the equipment and its advantages and disadvantages with regard to pharmaceutical production. An analysis was performed to compare the different technologies. Our findings confirm that there is a need for improved continuous small-scale systems for drying crystalline products without causing agglomeration and/or attrition in order to preserve crystal properties originating from careful engineering during the crystallization phase. The aim of this study was to provide information regarding operational capabilities of continuous small-scale drying equipment.