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It is generally recognised that carbon dioxide (CO2) emissions damage the environment. Carbon capture and storage offers the possibility of using fossil fuels for power production without releasing C02. In the proposed ZEITMOP power plant cycle hydrocarbon fuel is burned in a mixture of oxygen and C02, allowing easy separation of combustion products to capture the C02 for sequestration. Oxygen ion transport membranes (OTMs) provide oxygen. The original configuration of the cycle requires an OTM air separation unit, in which oxygen is separated from air and mixed with CO2, and a separate combustion chamber, in which fuel is burned in this mixture. Another possibility is to use a combined OTM combustion chamber and air separation unit. The oxygen is consumed by the combustion as soon as it permeates through the OTM, and the operating temperature of the OTM unit is the combustion temperature. The aim of the current research is to investigate the possible use of an oxygen ion transport membrane combustion unit in the ZEITMOP oxyfired cycle. OTM materials were compared. The combined ZEITMOP cycle was stimulated. During the course of the research a new cycle was developed and named the OFFCET cycle. The results of initial calculations on this cycle are described. An experimental rig was designed and built. Some work was also carried out on the ZEMPES cycle. It was found that the efficiency of the combined cycle using a perovskite unit would be very low due to the low operating temperature. The efficiency of the combined cycle with a fluorite unit may be higher than the efficiency of the separate cycle at the same combustion temperature. A fluorite OTM combustion unit operating at 1400°C would be of similar size to a perovskite OTM air separation unit operating at 875°C.
Foy, Kirsten : Investigation into the possible use of an oxygen ion transport membrane combustion unit in an oxyfired power plant. Dublin : Dublin Institute of Technology, 2007