End-point detection in high-shear granulation using sound and vibration signal analysis

The application of sound and vibration signal analysis for the end-point detection in high-shear granulation was investigated. Five microphones placed on different areas of the granulator were compared in order to find the optimum location. The optimum end-point of granulation as defined by a narrow distribution of intermediate-sized granules could be determined from the mean frequency, the 112 to 140 Hz sound pressure level and the power spectral density at 127.5 Hz from acoustic emissions measured by a microphone placed in the filtered air exhaust of the granulator. In addition, the vibration of the granulator was monitored with an accelerometer attached to the outside of the granulator bowl. The vibration signal also indicated changes in the wet granule properties during the granulation process, but the end-point could not always be clearly determined.