Wet granulation lines in pharmaceutical manufacturing facilities typically comprise a dryer that removes the excess moisture content after wet granulation. In this study, a semi-continuous dryer installed in the ConsiGma 25 wet granulation line was investigated. The goal was to highlight specific characteristics of this type of dryer, utilizing the available process data and the corresponding data obtained via material characterization. This paper addresses typical effects and issues associated with the dryer's setup and operation (e.g., unexpected cell temperature profiles, the effects of air flow and temperature on the granule properties, variations in the granule moisture between the dryer cells). Since in many situations the liquid-to-solid ratio is based on the properties of granules after the granulation step, the selection of inlet air flow rate and the inlet air temperature of the dryer as well as the overall line throughput (affecting the cell fill level in the dryer) are of particular interest from a practical point of view. This paper discusses these issues and provides suggestions on how to address them when setting up the process. A novel approach for characterizing the fluidization inside the dryer by means of quantifying the “smoothness” of the temperature profile is proposed. The paper should be viewed as a hands-on guideline, which highlights possible pitfalls during the process setup and offers solutions.
- Continuous wet granulation
- Fluid bed drying
- Fluidization characterization
- Online process monitoring