DEVELOPMENT OF ENHANCED ENERGY-EFFICIENT FLUIDIZED BED DRYING PROCESSES

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INTRODUCTION: Fluidized beds are widely used for drying processes in the pharmaceutical industry. Monitoring of the drying process to determine suitable operation conditions and an optimal endpoint is required to prevent losses and poor product quality. However, online measurement of moisture content in a fluidized-bed dryer is challenging. This research program will develop a new online monitoring technique based on the triboelectric behaviour of pharmaceutical powders in the drying process. Pharmaceutical powders are very prone to electrostatic charging by colliding and sliding contacts with walls and other particles during the drying process, and the change in this behavior can be utilized as an indicator of moisture content. * *OBJECTIVES: A comprehensive understanding of tribocharging behavior of pharmaceutical granules in fluidized-bed dryers is lacking. Therefore, an advanced understanding of tribocharging behavior in fluidized bed dryers is required to develop online monitoring for the drying process. Moreover, a better understanding of hydrodynamic phenomena influenced by tribocharging behavior is required for improved design of fluidized bed drying, which is an energy intensive process. The specific short-term objectives of this research are to 1) Advance understanding of pharmaceutical particle charging behaviour in a fluidized bed dryer; 2) Develop novel online monitoring techniques for fluidized bed drying processes; and 3) Conduct a numerical simulation of fluidized bed drying taking electrostatic force into account. **METHODS: Objective 1 will be conducted employing by both ex situ and in situ experimental approaches. In the ex situ approach, a free-dropping device will be employed to simulate contacts between particles and the wall and collisions among particles occurring in the fluidized bed. The flexibility of this approach allows for delineating effects of operating parameters within a broader range on electrostatic charging behaviors. In the in situ approach, tribocharging behavior will be explored in fluidized bed dryers at both the lab and pilot scale and under operatingconditions of relevance to the pharmaceutical industry. New triboelectric probes will subsequently be developed based on the advanced understanding of tribocharging behavior in fluidized bed dryers (Objective 2). Validation of the developed techniques will then be implemented in a commercial scale fluidized bed dryer. In parallel, numerical simulations will be carried out to complement experiment work. The numerical simulations will produce a wealth of detailed information within the fluidized bed at any desired scale, including temperature distribution, velocity distribution, moisture content, and charge distribution. The simulated results will further facilitate designs to optimize the process and improve the drying process (Objective 3). **IMPACT: The proposed research will produce comprehensive knowledge of the dynamics associated with electrostatic charging in fluidized bed dryers and will develop reliable and accurate online monitoring techniques for the optimal design of drying processes. The techniques developed will optimize operating conditions and provide better product quality control, thus minimizing both energy consumption and product loss. A better understanding of tribocharging behavior will also provide proactive measures in consideration of operator safety. My long-term goal is to develop innovative fluidization technologies with applications in renewable energy, pharmaceutical, food processing, fertilizer, and agriculture industries. I aim to build a world-class research program in fluidization and particle technologies with applications geared towards green processes, renewable energy, and sustainable development.