Direct-fired oxy-combustion supercritical-CO2 power cycle with novel preheating configurations -thermodynamic and exergoeconomic analyses

Abstract

Energy, exergy, and exergoeconomic analyses of novel direct-fired oxy-fuel combustion supercritical CO2 cycle with preheating and dry-cooling are introduced. Novelty aspects of the study include the preheating process effect on the performance of sCO2 cycle fired by oxy-combustor at moderate turbine inlet temperatures. Three cycles are investigated; original layout without-preheater (configuration M1), integrated preheater with the system in parallel with low-temperature recuperator (configuration M2) and integrated preheater in parallel with both high and low-temperature recuperators (configuration M3). Results show that the integrated preheating process improves cycle efficiency by 3.7% in M2 and by 8.3% in M3. The preheating improves the performance of recuperator by reducing the “pinch-point” effect as a result of the split flow downstream the compressor. The optimization of the split ratio resulted in cycle efficiency of 45.8% in M3, 41.2% in M2, and 37.5% in M1 for 50MWe system at 750 °C turbine inlet temperature. The overall exergy efficiency is improved from 78.1% in M1 to 86.5% in M2 and 88.8% in M3. The exergoeconomic analysis; the first applied to direct-fired oxy-fuel sCO2 cycle, showed reduction in total product cost per unit exergy by 13.92% in M2 and 34.96% in M3.