Techno-economic assessment of the Allam cycle for different plant sizes, oxygen purities and heat integration with external sources

This study investigates the energy and economic performance of the Allam cycle, a novel direct-fired, oxygen combustion supercritical CO2 cycle specifically suitable for CO2 capture and storage applications. The cycle is assessed and optimized for different plant sizes (in the range 50 MW - 400 MW of net electric power output), purity of the fed oxygen (95 %, 97 % and 99.5 % O2 molar concentration) and heat recoverable from the Air Separation Unit and/or external processes. The analysis includes the preliminary design of the turbomachines with literature correlations for their efficiency and the detailed simulation of the CO2 purification unit. The analysis shows that the optimal oxygen purity for the plant efficiency is 99.5 % and the net electric efficiency (including all auxiliary units) might vary in the range 48.7 % to 56.1 % depending on the plant size and heat recoverable from external processes (e.g., ASUs). The economic analysis of the cycle, performed for a 400 MW plant, indicates a promising specific total plant cost (2490 /kW) and a competitive cost of electricity, approximately 10.4 % lower than a benchmark combined cycle with post-combustion capture system.