Optimization and comparison of the two promising oxy-combustion cycles NET Power cycle and Graz Cycle

Carbon capture and storage (CCS) is considered an effective measure to reduce the anthropogenic CO2 emissions. Oxy-combustion with a theoretical capture rate of 100% is a very promising CCS technology. In order to show the potential of oxy-combustion two highly-efficient power cycles, the NET Power cycle and the Graz Cycle, are thus thermodynamically optimized and compared at full load for firing with natural gas.

The simulation of both cycles is carried out using the thermodynamic simulation software IPSEpro. Particular attention is paid to provide the same boundary conditions and assumptions for both processes to ensure a correct comparison. As a starting point a base case for each cycle is simulated based on the literature data. Both power cycles are then optimized by varying the main cycle parameters using a genetic algorithm. The optimized processes show a slightly higher net efficiency considering oxygen supply and CO2 compression for the Graz Cycle with 53.5% compared to 52.7% for the NET Power cycle. Moreover, the main differences of both cycles are discussed and the impact of assumptions of component losses and efficiencies as well as the minimum cycle temperature on both cycles is discussed