The effect of granule moisture on passive acoustic emissions in a V-blender

Abstract

The development of process analytical technologies (PAT) can improve the efficiency and product quality during pharmaceutical manufacturing. The objective of the current research was to investigate the potential application of passive acoustic emission monitoring to detect changes in solids moisture content as the solids tumble in a V-blender. Trials were conducted with wooden beads, sugar spheres and two placebo formulations of pharmaceutical granules in a V-blender. Vibrations from acoustic emissions were measured using PCB Piezotronics accelerometers with ICP signal conditioners. A wavelet filter was applied to the measured acoustic emissions to remove vibrations from the tumbling motion of the V-shell, allowing a focus on information about particle motion and interactions within the V-shell. Three signal features were identified in the acoustic emissions with each feature being attributed to phases of the particle motion within the V-shell. The maximum feature amplitude was found to vary with solids moisture content; both particle mass and flowability had an impact on the acoustic emissions amplitude. Particle flowability changes were correlated to a critical moisture content obtained from solids drying profiles. The measured vibrations from passive acoustic emissions reflected changes in particle motion and interactions within a V-blender as the solids moisture content varied demonstrating the potential of passive acoustic emissions measurements to obtain critical process information inline and in real time.