Performance Assessments of a Novel Oxy-Fuel CO2 Cycle

Abstract This paper presents a novel way of improving CO2 intensity simple cycle gas turbines. We present a novel combined cycle that consists of an integrated semi-closed oxy-fuel gas turbine topping cycle and a sCO2 bottoming cycle. This sCO2 bottoming cycle offers compactness, operation without water or steam, and improves overall cycle performance. The semi-closed oxy fuel gas turbine working fluids are mainly CO2 and water making it feasible to separate CO2 by condensing water vapor. Also, since O2 is used as an oxidizer instead of air in the combustion, NOx emissions are almost zero. Here we analyze a generic mid-sized oxy-fuel gas turbine cycle. The air separation unit and the CO2 compression were also modeled, and their parasitic loads included in the overall performance. We further studied three sCO2 bottoming cycle configurations for optimizing the oxy-fuel gas turbine heat recovery. The analyzed sCO2 cycle configurations were simple sCO2, cascade sCO2 and advanced sCO2 cycle. This paper also studies the oxy-fuel gas turbine integration with sCO2 at different gas turbine pressure ratios varying from 13 to 55 with a turbine inlet temperature of 1500°C. The advanced sCO2 output was almost 16% higher than simple sCO2 configuration. The overall cycle efficiency for advanced sCO2 was around 10% higher than simple sCO2 configuration in all studied pressure ratios. The study also shows that the overall cycle output and efficiency were almost flat at pressure ratio above 35. The overall cycle output for advanced sCO2 was 110 MW and the overall efficiency was 45.7% at pressure ratio 35. Furthermore, the study includes a sensitivity study on the advanced sCO2 at pressure ratio 35 and different cooling ambient temperatures. Here we show that the advanced sCO2 cycle output dropped by 19% when the ambient temperature increased from 20°C to 45°C. The advanced CO2 cycle configuration has shown to be an interesting decarbonization solution for simple cycle gas turbines, more specifically when operating in remote locations with limited access to water or steam. The paper is based on granted GE patent WO/2023/009161.