Energy-based analysis of cone milling process for the comminution of roller compacted flakes.

Cone mill is commonly used for the milling of wet and dry agglomerates in the pharmaceutical industry as it is capable of producing milled granules with desired size characteristics. The aim of this study was to evaluate the various cone mill process parameters in terms of milling rate and energy consumption for the comminution of roller compacted flakes. A placebo formulation containing microcrystalline cellulose, lactose and magnesium stearate was used to evaluate the milling performance. Results of this study showed that higher milling rate was obtained with the combination of higher impeller speed, teethed round sidearm impeller and grater screen surface profile. Either one of the later two parameters when present in any mill setting was found to be capable of shortening the residence time of flakes inside the milling chamber, thus resulting in a higher milling rate. On the other hand, selection of appropriate screen surface profile and impeller speed was very important at lowering the effective specific energy consumption during milling. Grater screen surface profile and impeller speed between 2000 and 2400 rpm were found to act synergistically as the best combination for an energy sparing process. Impeller sidearm shape was found to have no significant effect on energy consumption.

Application of near-infrared spectroscopy in real-time monitoring of product attributes of ribbed roller compacted flakes.

This study assessed the utility of near-infrared (NIR) spectroscopy for the real-time monitoring of content uniformity and critical quality attributes (tensile strength, Young's modulus, and relative density) of ribbed roller compacted flakes made by axially corrugated or ribbed rolls. A custom-built setup was used to capture off-line NIR spectra from the flakes containing micronized chlorpheniramine maleate, microcrystalline cellulose, lactose, and magnesium stearate. The partial least square regression method was employed to build calibration models from these off-line NIR spectra using experimental design and validated using test set validation. During calibration model development, various factors, such as spectral acquisition mode, probe positioning, spectral preprocessing method, and beam size, were investigated to improve the prediction ability of the models. The statistical results obtained for calibration models and their validation revealed that dynamic spectral acquisition and proper probe positioning were very crucial to minimize the incorporation of variability in NIR spectra resulting from the flake's undulation. Calibration and validation statistics also suggested the importance of selecting appropriate spectral preprocessing method and beam size. In this study, best calibration models resulted from standard normal variate followed by first derivative preprocessed dynamic spectra captured using beam size ~1.2 mm. Best calibration models constructed from off-line NIR spectra were used in real-time analysis of flake attributes. Finally, adequacy of best calibration models was established from real-time prediction results. Overall, with the proposed setup, it was possible to monitor the roller compaction process in real time for various properties associated with the ribbed flakes in a rapid, efficient, and nondestructive manner.