Comparison of three different methodologies of pressure signal processing to monitor fluidized-bed dryers/granulators

The monitoring of the particle moisture content and the particle size has a great importance in the fluidized bed drying and granulation processes. Due to the implementation of the Process Analytical Technology initiative in the pharmaceutical industry, there is an increasing interest to apply on-line monitoring tools for process control. In this paper, we compare three different techniques of signal processing applied over pressure fluctuation measurements in order to monitor on-line the moisture of the particles in a fluidized bed dryer and the particle size in a fluidized bed granulator. These techniques are: (i) dominant frequency analysis, (ii) narrow-band standard deviation analysis and (iii) attractor comparison tool. The results show that the narrow band standard deviation method provides the best correlation between the data derived with the pressure fluctuation probe and the granule moisture content and particle size respectively.

• We monitor fluidized bed drying and granulation by pressure fluctuations.
• Dominant frequency analysis, standard deviation of narrow band frequency analysis and the attractor comparison were applied.
• The standard deviation of the narrow band filtered signal varies linearly with the granule size.