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

• A detailed techno-economic model of the Allam cycle is developed. • The optimal oxygen purity for the net plant efficiency is 99.5% mol. • The efficiency is relatively high (> 51 %) in the range 400 MW-100 MW. • The cycle is economically competitive against post-combustion capture. This study investigates the energy and economic performance of the Allam cycle, a novel direct-fired, oxygen combustion supercritical CO 2 cycle specifically suitable for CO 2 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 % O 2 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 CO 2 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.