Thermodynamic Optimization and Part-load Analysis of the NET Power Cycle

This paper performs the thermodynamic optimization and part-load analysis of the NET Power cycle (also called Allam cycle), a natural-gas-fired oxy-combustion cycle featuring 100% CO2 capture level, very high net electric efficiency, and potentially near-zero emissions level. To determine the maximum achievable cycle efficiency and optimal cycle variables, an Aspen Plus flowsheet including accurate first-principle models of the main equipment units has been developed and combined with a black-box optimization algorithm. The corresponding maximum cycle efficiency is equal to 55.35% (with 100% CO2 capture). Optimization-based sensitivity analyses are performed to explore the neighborhood of the maximum efficiency cycle design with the aim of finding combinations of the cycle variables which lead to reduced costs and thermo-mechanical stress of the most critical components. Finally, the part-load performance of the optimized NET Power cycle has been analyzed. Results indicate that in the load range 100-40% the cycle (excluding the ASU) features a considerably lower efficiency decrease compared to a standard combined cycle. This result, showing the possibility of efficiently operating the cycle also at part-loads, further increases the attractiveness of the NET Power cycle.