A Thermoeconomic Evaluation of CO2 Capture with Focus on Gas Turbine-Based Power Plants

University dissertation from Department of Energy Sciences

Abstract: The increasing emissions of carbon dioxide from fossil fuel burning are today thought to be one of the main contributors to global warming. At the same time, developing countries are striving for an increased welfare and burning more fossil fuel, which in turn is augmenting the greenhouse gas effect. In this thesis the current understanding of the connection between greenhouse gases and the climate are illuminated, while some contradictory theories are also presented. Believing carbon dioxide to be a threat to the climate, which has been sufficiently evidenced to take actions against it, one possible option is to capture carbon dioxide in power plants and permanently store it underground. In this thesis different technologies for carbon dioxide capture are described. A thermodynamic model for post-combustion capture of carbon dioxide from flue gas is detailed, including thermodynamic models for a humidifier and exhaust gas condenser; components much needed in the proposed power plant layouts for power production with low or no emissions of carbon dioxide. Furthermore, an economic model suitable for modelling power plant schemes with low emissions of carbon dioxide in an economic environment with changing fuel prices and incentives for reduced emissions levels, are also presented. In a number of case studies, the thermodynamic and thermoeconomic performance of such proposed power plant layouts are compared, often with a standard combined cycle used as a reference base. In some case studies the performance, thermodynamic or thermoeconomic, have been optimised with an optimisation tool based on genetic algorithms, a method also thoroughly explained in this thesis. Case studies include among others; combined cycle gas turbines and humid air turbines with and without CO2 capture, pre-combustion combined cycle gas turbines and AZEP combined cycles. An overview of different methods for transport and storage of CO2, together with cost estimates and storage potential are also detailed in this thesis. A conclusion is made with the positive message that there seems to be a viable business case for carbon capture and storage with current high prices both on oil and certified emissions rights.

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