Exergy-Based Investigation of a Coal-Fired Allam Cycle

Abstract The Allam cycle is a novel cycle that capitalizes on the unique thermodynamic properties of supercritical CO2 and the advantages of oxy-fuel combustion for power generation and CO2 capture. This study aims to confirm the outstanding performance of a coal-fired Allam cycle and with the aid of an exergetic analysis to provide detailed important information on the real thermodynamic inefficiencies within the cycle. The results show that the overall exergetic efficiency is 40.6%, with near 100% carbon capture. The highest exergy destruction occurs within the gasifier, which contributes 29.1% to the overall exergy destruction, followed by the combustion chamber (17.4%), the air separation unit (7.4%) and the turbine (4.1%). In addition, the results obtained from the exergetic analysis in this study are compared to those of a gas-fired Allam cycle. The contribution of the exergy destruction of the combustor in the gas-fired Allam cycle is higher than the total share of the gasifier and the combustor of the coal-fired Allam cycle in the system exergy destruction. The sensitivity analysis shows that the specific power demand of the air separation unit, as well as the turbine inlet pressure, outlet pressure and isentropic efficiency have significant impacts on the overall exergetic efficiency.