Thermodynamic Performance Analysis of New Gas Turbine Combined Cycles With No Emissions of Carbon Dioxide

Abstract

In the context of the reduction of the carbon dioxide (CO2) emissions as prescribed by the Kyoto protocol, this paper describes a thermodynamic performance analysis of new gas turbine combined cycles with no emissions of CO2 and nitrogen oxides. Three new similar cycles belonging to the same typology are proposed. These cycles use water/steam as working fluid, which is compressed in liquid and vapour phase, and the internal combustion process, which takes place between syngas and pure oxygen. The top Brayton cycle and the bottom Rankine cycle are integrated together. The syngas is produced by steam-natural gas reforming with internal chemical heat recovery. The CO2 produced in the combustion is captured simply by water condensation from the exhaust gas and liquefied to be stored. A simulation analysis has been performed to evaluate the net efficiency and the net specific work of the cycles. Varying the most important operative variables and using the least square regression and 2k factorial design techniques, a very large sensitivity analysis has permitted to highlight the performance behaviour of the cycles. Including the energy penalty due to the liquefaction of CO2 and to the oxygen production and adopting standard operative conditions, the LHV-based net efficiency and the net specific work may exceed 50% and 1000 kJ/kg, respectively.