Date of Award


Document Type

Master Thesis

Degree Name

Masters of Science (Research)


Chemical & Process Engineering

First Advisor

Cilian Ó Súilleabháin

Second Advisor

Ian O'Sullivan


Drying of pharmaceuticals and fine chemicals is often accomplished under vacuum conditions to enhance energy efficiency and to avoid overheating of thermo sensitive materials. This project aims to study vacuum drying operations to obtain a better understanding of this process so as to optimize drying performance. This project obtained industrial data collected from a range companies in Ireland.

Pharmaceutical companies started assessing processes and making changes to drying processes from 2004 onwards; these initiatives are due to economic pressures, environmental issues and the Process Analytical Technology (PAT) initiative launched by the FDA in 2004.

Vacuum drying has been used in industry for at least eight decades. Apart from control systems, little other significant research has been published during the past thirty years. There is a lack of published information on practical issues; this is particularly marked in the pharmaceutical industry, probably due to the constraints of FDA regulations.

This study presents a description of the different vacuum drying configurations and equipment currently in use in industry. Solvent recovery rates, disposal and destination of the solvent evaporated from vacuum dryers are also assessed. Drying curves from industrial dryers are studied for a variety of products. This research also reviews relevant instrumentation and techniques for monitoring operations and for end point determination, including moisture content analysis and inferential measurements. Miscellaneous issues have been identified in industrial vacuum drying such as sampling, balling, solvent boiling, formation of solvent pockets, puffing of product and dryer cleaning.

Industry uses a variety of methods for end-point determination so as to reduce energy consumption and increase efficiency. This project concludes that there are many opportunities to enhance vacuum drying operations and the dissemination of practical information is a necessity as no standard procedures are in place. This area warrants further research as many gaps have been identified during this study.

This project is funded by the Environmental Protection Agency (EPA) under the Environmental Technologies Masters Scholarship Programme.

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