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theses

Drying processes are common in the chemical, pharmaceutical and food industries. It is one of the traditional methods that removes moisture or solvents to provide stable products and/or semi-finished products. It is also known that the drying process is energy intensive. It has been reported that an average of 12 % of all energy consumed in the world is used for drying, and the cost of drying could reach up to 60 % - 70 % of total cost of investments. Therefore, the optimal operation of the drying process is sought to meet the requirements for cost-effective manufacturing.
In the pharmaceutical industry, the particulate ingredients are often granulated to improve their flowability and uniformity. A fluidized bed gas-solid drying is usually followed to remove the moisture that is introduced during the granulation. Before a new formulation is launched into commercial size units, it is prevalent to do lab-scale tests to understand its characteristics. Although a number of studies have been done on fluidized bed scale-up, practical scale-up rules for fluidized bed drying still remain unclear. This work will start with understanding several important operational parameters for fluidized beds. Then, a practical scaling rule will be introduced to predict the drying behavior of a pharmaceutical excipient in large scale units based on lab-scale results.
Another part of the work will be to try and use the knowledge gained from the batch mode fluidized bed dryers to predict the behavior of a continuous mode fluidized bed dryer. Several pharmaceutical manufacturers are moving towards continuous manufacturing due to its potential to improve agility, flexibility, and robustness.The fluidized bed unit operation can be easily implemented as a continuous process for drying. One of the most important tools to characterize a continuous unit is the residence time distribution (RTD). It describes the probability distribution of the material staying in the unit. The RTD will be investigated in this work via a tracer study. With the RTD model for flow in the continuous fluidized bed and drying kinetic models constructed with data from lab-scale experiments, we will develop an approach to predict the final moisture content of the product. The final moisture content variations caused by changes in the operating condition or changes in the feed material will also be evaluated.

ETD_9712

Ph.D.

Includes bibliographical references

doi:10.7282/t3-5bsf-9314

ETD doctoral

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