Amine und Aminmischungen zur CO2-Absorption aus Kraftwerksrauchgasen und ihr Energiebedarf zur Regeneration

Dissertation von Anke Schäffer
Universität Stuttgart, 2013

To reduce the greenhousegas CO2 it may be captured and stored. Thereby post-combustion capture with amine scrubbing is one promising option to minimize CO2 emissions from fossil-fuel power plants. An aqueous solution of 30 mass% monoethanolamine (MEA) is often used for CO2 absorption. Its thermal regeneration requires a high energy damand, reducing the overall power plant efficiency up to 15 %-points. In order to minimize the energy requirement, it is the aim of this thesis to identify alternative solvents to MEA for a more energy efficient CO2 capture.

To this end a methodology based on screening results for an early estimate of the regeneration energy is given in this thesis. At first the absorption and desorption behaviour of several aqueous solutions of amines and amine mixtures are acquired in this broad screening. Then solvents with advantages compared to MEA are selected. These are a high absorption rate and high cyclic capacity in combination with a low 90 °C loading. Subsequently solvent specific data required to calculate the regeneration energy are determined in an extensive characterization. These include the vapor-liquid-equilibrium data at absorption and desorption conditions as well as the enthalpy of absorption. Based thereupon a model is developed to calculate the energy demand for regeneration. The results show that the regeneration energy compared to MEA can be reduced specifically for solvents featuring a low loading at 90 °C and a high cyclic capacity, whereby the stability of the CO2-amine-bond plays a decisive role.

Finally, in order to estimate the energy demand a correlation is established based on the screening results and applied to all studied solvents. The results show that, especially secondary amines and amine mixtures of poly- and secondary amines with a carrier amine have strong potential to optimize the energy demand. In comparison to MEA it can be reduced by more than 40 % while still achieving similar kinetics.

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