Techno-economic analysis of an integrated gasification direct-fired supercritical CO2 power cycle

Abstract

This study describes recent systems analyses of coal-fueled, oxy-fired direct supercritical CO2 (sCO2) power cycles, which are inherently amenable to carbon capture and storage (CCS) processes. In this plant, coal is gasified in an entrained flow gasifier, cleaned of sulfur and particulate matter, and supplied to the sCO2 cycle’s oxy-combustor, where it burns with oxygen in a high pressure, heavily diluted sCO2 environment. Following expansion of the combustion products through a turbine and recuperation of its thermal energy, water is condensed from the working fluid, which is recompressed for return to the combustor, with a portion of the CO2 exhausted from the cycle for CCS.The conceptual designs for two coal-fueled direct-sCO2 power plants are included in this study, one as a baseline sCO2 plant, and another which includes improved thermal integration between the sCO2 cycle and the gasifier. Parametric analyses are used to optimize the overall plant configuration and operating conditions, from which the capital cost and operating expenses of the plant are estimated, and the cost of electricity (COE) calculated. The study results yield plant thermal efficiencies of 37.7% (HHV) and 40.6% for the baseline and improved sCO2 cases, including CCS. These efficiencies are a significant improvement on the 31.2% efficiency of the same gasifier in an integrated gasification combined cycle (IGCC) plant configuration with CCS, and are also shown to be comparable to more advanced IGCC systems and other coal-fueled direct sCO2 plants with CCS. Detailed economic analyses yield COE results of $137.3/MWh and $122.7/MWh for the baseline and thermally integrated sCO2 plants, respectively, representing 10% and 20% improvements on the reference IGCC COE of $152.6/MWh, with CCS. Recommendations are made for alternative gasification systems and modifications to the thermal integration between the gasifier and direct sCO2 system, which should further improve plant performance relative to alternative systems.