Thermodynamic benchmarking of sCO2 Allam cycle against alternative oxy-fuel cycles: A comparative analysis

To explore the potential of oxy-fuel technology, a detailed thermodynamic analysis is performed for four different oxy-fuel combustion cycles: the SCOC-CC, Matiant cycle, S-Graz cycle, and Allam cycle. Based on the literature data, these thermal cycles are modeled and simulated at full load using commercial software Aspen Plus with the same input and boundary conditions. The results show that the Allam cycle and S-Graz reach the highest net energy efficiency with 56.04% and 53.19%, respectively. The Matiant cycle and SCOC-CC have lower efficiencies at 50.02% and 45.23%, respectively. The exergy efficiency is also higher for the Allam cycle (52.87%) and the S-Graz cycle (50.18%). Moreover, the CCS efficiency penalty is comparatively higher for S-Graz, SCOC-CC, and Matiant, with 3.88%, 1.78%, and 1.70%, respectively. This is primarily because of the lower condenser pressure than the Allam cycle, which has a penalty of 0.42%. The ASU efficiency penalty is consistent at 10.31% for all cycles due to the same delivery pressure, flow rate, and oxygen purity. However, in the Allam cycle, it is marginally higher by 0.71 ppt due to an extra oxygen compressor. Furthermore, exergy destruction and entropy generation rates are particularly significant in the combustor, turbine, recuperator and condenser across all cycles. The results also indicate that the turbine main parameters, such as inlet temperature, inlet pressure, outlet pressure, and condenser pressure, strongly influence the system overall performance. The Allam cycle generally stands out for its high thermal efficiency and simple configuration. • Thermodynamic modelling of four oxy-fuel cycles with ASU and CCS integration. • CCS and ASU effects quantified under full-load for performance comparison. • Exergy analysis identifies weak spots to improve overall cycle efficiency. • Comparative study shows strengths and improvement potential of each cycle.