Proportional control of moisture content of granules by adjusting inlet air temperature in fluidized bed granulation using near-infrared spectroscopy

•Proportional feedback control was effective in controlling moisture content.•Variation in the particle size of granules can be minimized by feedback control.•Feedback control can be introduced without changing the granulation conditions.

For process control of fluidized bed granulation process, we investigated proportional (P) moisture content control via adjustment of inlet air temperature in proportion to the difference between measured and target moisture content of granules. Here, we first validated P moisture content control by comparison with bed temperature control. We then confirmed that P moisture content control is effective in maintaining the moisture content, and in minimizing the variance of the particle size of granules following granulation. Furthermore, we observed that when the target temperature was higher than the measured value of inlet air temperature the P moisture content control response was accelerated. In contrast, when the target temperature was less than the measured value of inlet air temperature (<50 °C) the response was delayed. In summary, P moisture content control has good scalability and can be introduced without changing granulation conditions in the development of orally administered pharmaceutical products.