[Simulation of falling rate stage in drying of TCM pills: mechanisms, models, and applications]

Drying, as a crucial stage in the preparation of pills, serves as a key step in ensuring pharmaceutical quality. During this process, the adoption of a scientifically drying method and the precise control of critical parameters such as temperature and humidity enable effective regulation of drying uniformity, thereby maximizing the retention of pharmacological activity while optimizing pill appearance, hardness, and disintegration time and ensuring the good quality of the drugs and their stable release. The drying process of pills is predominantly characterized by a falling rate drying stage. In this stage, if the rate of internal moisture diffusion fails to match the rate of surface moisture evaporation, quality defects such as surface hardening, cracking, and false drying may occur. These issues increase the resistance to water vapor mass transfer, further reducing the drying rate. At present, simulation technologies have been increasingly applied in the study of drying processes for TCM pills, achieving significant progress in process optimization, equipment improvement, and quality control and thereby providing theoretical and technical support for quality enhancement. However, existing models largely rely on empirical parameters and lack accurate databases of physical properties, leading to discrepancies between simulation results and practical outcomes. Consequently, future research should focus on integrating artificial intelligence-assisted techniques for model parameter identification and optimization, applying digital twin technology for real-time monitoring of drying processes, and advancing toward sustainable production characterized by green, low-carbon, and energy-efficient approaches. Such efforts will continuously overcome technical bottlenecks in pill drying and accelerate the upgrading of production equipment for TCM pills.