Evaluating Resonant Acoustic Mixing as a Wet Granulation Process.

Control of powder properties is crucial for industrial processes across the food, pharmaceutical, agriculture, and mineral processing industries, and granulation is an important tool for providing agglomerated particles with controllable properties. However, existing granulation processes are not readily integrated with other processing steps and are not appropriate for some types of materials. Adding resonant acoustic-based granulation to the toolkit has the potential to widen the achievable parameter space and, importantly, integrate granulation into chemistry and blending operations that are already being performed on the RAM platform, resulting in process intensification. Here, we demonstrate the formation of granules with particle sizes of ca. 1-3 mm in LabRAM II and examine the formation mechanisms in the context of common wet granulation processes. The RAM granulation process followed here involves first forming a large "doughball" agglomerate and then driving its breakup by evaporating the solvent, while impacting the doughball against the container walls. We show that this process is similar to the destructive nucleation model for high-shear wet granulation with the solvent evaporation in our case leading to the decrease in the liquid saturation of the doughball, a corresponding decrease in its tensile strength, and the acceleration in the RAM establishing the impact pressure when the doughball contacts the walls. This work provides a foundation for granulation process design with a resonant acoustic mixer and, through its link to existing granulation mechanisms, provides a path to a deeper understanding of the process.