ISBN 978-3-8439-1630-1

978-3-8439-1630-1, Reihe Verfahrenstechnik

Martin Dittmar
Rieselfilmtechnik für drucklos betriebene Absorptionskolonnen in Experiment und Simulation

225 Seiten, Dissertation Technische Universität Dortmund (2014), Softcover, A5

Zusammenfassung / Abstract

A transfer of structured high performance packings, commonly used in absorption columns in the (petro-)chemical industry, which are designed and used prior at gauge pressure due to process related issues for non-pressurized and/or atmospheric absorption tasks is possible to a limited extent only. A possible application area is the currently investigated CO2-sequestration of flue gases from power plants. If such structured packings are used here, the gas side pressure loss will lead, together with the process related huge flue gas volume streams, to high operational costs for the blower. Furthermore this will lead to uncommon big column diameters, which are hard to operate due to occurring maldistributions of gas and liquid flow.

The usage of falling film technique, where thin wavy liquid films flowing downwards on vertical. plane walls, offers high mass transfer coefficients with a - construction related - significantly lower gas side pressure loss at the same time. A widespread application in the process industry failed so far as the mass transport mechanisms, which are dominated by complex flow structures inside the falling films, are not fully understood.

This work describes on the one hand the process optimization with respect to CO2 absorption of flue gases with the use of falling film technique at a technical center plant. A novel process concept for the continuous absorption/desorption process is introduced, which allows locally high liquid loads to ensure wavy falling films in the absorption column. Absorptivity measurements with three different scrubbing liquids and packings - beneath a falling film packing prototype - are provided. On the other hand two-phase flow CFD-simulations with free interfaces and mass transport

of wavy liquid films are modeled with FLUENT 13.0. The hydrodynamics and the position of the free interface are modeled with modern CFD-tools in a first step. The results are validated with experimental measurements from the literature. In a second step a highly spatial and temporal resolution of the CO2 species transport in the falling films is achieved. This ensures an up to date unpublished closeness to reality of the found transport mechanisms and deducible quantitative results for the mass transport in wavy falling liquid films.

The results presented are a valuable basis for the construction of an appropriate pilot plant towards widespread industrial application of the wavy falling film technique.