Thermodynamic and Economic Investigation of an Improved Graz Cycle Power Plant for CO2 Capture

Abstract

Introduction of closed cycle gas turbines with their capability of retaining combustion generated CO2 can offer a valuable contribution to the Kyoto goal and to future power generation. Therefore research and development at Graz University of Technology since the 90’s has lead to the Graz Cycle, a zero emission power cycle of highest efficiency. It burns fossil fuels with pure oxygen which enables the cost-effective separation of the combustion CO2 by condensation. The efforts for the oxygen supply in an air separation plant are partly compensated by cycle efficiencies far higher than 60%. In this work a further development, the S-Graz Cycle is presented, which works with a cycle fluid of high steam content. Thermodynamic investigations show efficiencies up to 70% and a net efficiency of 60% including the oxygen supply. For a 100 MW prototype plant the layout of the main turbo-machinery is performed to show the feasibility of all components. Finally, an economic analysis of a S-Graz Cycle power plant is performed showing very low CO2 mitigation costs in the range of 10 $/ton CO2 captured, making this zero emission power plant a promising technology in the case of a future CO2 tax.