ISBN 9783843952217

978-3-8439-5221-7, Reihe Verfahrenstechnik

Felix Ortloff
Separation of CO2 from Biogas using Ionic Liquids

222 Seiten, Dissertation Karlsruher Institut für Technologie (2022), Softcover, A5

Zusammenfassung / Abstract

In this work, the use of ionic liquids (IL) for separating CO2 from biogas was evaluated. The experimental part of this work consists of physical & chemical characterization of IL, examinations on hydrodynamics and mass transfer in a technical scale absorption column and testing of the two most favorable IL based separation processes in a mini plant setup. Based on the findings of this work, a new CO2 separation process for biogas upgrading is proposed which operates according to the principle of chemical pressure swing absorption. This means that absorption and desorption column are operated at an equal temperature level of approximately 80 °C, the driving force for separation of CO2 is applied by operating the desorption column under vacuum. While the negligible vapor pressure of ionic liquids enables the concept, the increased temperature compensates their common disadvantage, namely their high viscosity, which limits their mass transfer performance when applied in conventional mass transfer equipment.

As washing medium, a mixture of [BDiMIM][BTA] with 10 wt% of [BDiMIM][Pro] was used, which showed promising physical and chemical property data in terms of thermal stability and CO2 uptake. Experiments on hydrodynamics and mass transfer led to the derivation of an adapted correlation for the prediction of liquid hold-up and volumetric mass transfer coefficient in packed bed absorption columns, taking into account the higher viscosity and the lower surface tension of IL.

Finally, an economic analysis was conducted to evaluate the potential of the proposed IL based separation process. The results show that based on realistic future IL prices the proposed process can be beneficial in comparison to state-of-the-art processes. The results showcase that when not only the solvents are tailored to the process, but the process is also tailored to the solvent specific advantages, potentials for optimization still exist, even in state-of-the-art applications.