Thermodynamic and efficiency optimization of the Allam Cycle with and without exhaust gas recompression

This work focuses on the comparison between two patented configurations of the Allam Cycle: the basic scheme and the recompressed one. The two Allam cycle schemes, including the cryogenic CO 2 purification and compression unit, have been accurately modelled with Aspen Plus v14. For each scheme, two cases are studied: a case featuring heat integration with the Air Separation Unit and a case without external heat supply. The independent cycle design variables (pressures, temperatures) are numerically optimized to maximize the net electric plant efficiency. The results indicate that, without external heat integration, the cycle with exhaust gas recompression achieves net electric efficiency considerably higher than the basic cycle (48.2 % vs. 51.3 %). However, the efficiency advantage of the recompressed cycle diminishes in the case with external heat integration (51.5 % vs. 53.3 %). When the external heat is further increased, the efficiency of the two cycles tend to converge to approximately 55 %. Sensitivity analyses are also conducted to assess the impact of the performance of the main components (compressors, turbine, air separation unit, heat exchangers) on the efficiency of the two cycle schemes.