This book provides support to engineers as well as graduate students in their daily design work within the industry or for the development of new plants. It investigates the key issues relating to the fluid dynamic design of packed columns used in rectification, absorption and stripping (desorption) under vacuum, normal pressure and up to 100 bar and liquid-liquid-extraction, which are relevant in waste air and wastewater technology. The author presents a standardised model, which is valid for any type of packing and can be used to calculate the gas velocity at flooding point as well as the liquid hold-up and the pressure drop throughout the entire operating range for random packings, stacked packings elements, tube columns and structured packings with different flow channel angles. The book also contains packing parameter data for approx. 200 random and structured packings. In addition to outlining the fundamental principles of fluid dynamics, it presents numerous examples of practical application.