Charakterisierung perowskitischer Hochtemperaturmembranen zur Sauerstoffbereitstellung für fossil gefeuerte Kraftwerksprozesse

摘要

In this thesis thermochemical properties of mixed conducting, perovskite-type materials were investigated. Those materials are assumed to be applicable as gas separation membranes in the oxyfuel process. Here, the materials should produce the required oxygen more energy-efficient than cryogenic air separation. High-temperature materials which are applicable for this purpose are gastight and exhibit a high oxygen permeation rate and a preferably low thermal expansion coefficient. Moreover, the materials are long-term stable under power plant relevant conditions. The aim of this work is a better understanding of the material behaviour. Furthermore, on the basis of the results it should be possible to draw conclusions concerning the suitability of the material for application in oxyfuel power plant processes. Therefor, the influence of the chemical composition (doping elements and stoichiometry) of the perovskites, the temperature and the oxygen content in the ambient atmosphere on the thermochemical properties are studied systematically. In the framework of this thesis it could be stated that the thermochemical behaviour of prospective membrane materials strongly depends on the above mentioned parameters. In addition, the degradation behaviour (thermochemical stability) of the materials was investigated. The degradation behaviour influences the suitability of the material to be used in oxyfuel power plant processes. Here, the influence of the chemical composition of the perovskites, the temperature and the CO2-concentration in dry and humid atmospheres was also studied. On the basis of the results it could be stated that the thermochemical stability strongly depends on the surrounding atmosphere and on the chemical composition of the perovskites.