Thermal efficiency of advanced integrated coal gasification combined cycle power generation systems with low-temperature gasifier, gas cleaning and CO2 capturing units

Advanced integrated coal gasification combined cycle (A-IGCC) systems have been proposed to obtain higher thermal efficiency than that of IGCC systems by recuperating exhaust heat from a gas turbine to provide the heat source for a gasifier. The performances of the A-IGCC systems with a low-temperature dual-bed fluidized bed gasifier, gas cleaning, CO2 capturing, and the most advanced (1650 °C-class) gas turbine units were evaluated using Aspen Plus®. Net thermal efficiency of the A-IGCC model with hot gas desulfurizing unit using ZnO and TiO2 was 53.6% and that with cold gas desulfurizing unit using Selexol® process was 52.0% without CO2 capturing when the cold gas efficiency (CGE) in the gasifier was 80.1%. The net thermal efficiency can be increased to 54.7-57.2% by improving CGE from 80.1 to 85.0%, suggesting the improvement of cold gas efficiency in the gasifier is critical. CO2 emission factors of the A-IGCC system are 505-520 kg-CO2/MWh (CGE = 80.1%) and 468-490 kg-CO2/MWh (CGE = 85.0%), and can be decreased to 39.7-112 kg-CO2/MWh with 80-95% of CO2 capturing. Compliance to the CO2 emission factor target (< 499 kg-CO2/MWh) for coal-fired power generation systems can be achieved without CO2 capturing by developing gasifiers whose CGE is 85.0% and integration with 1650 °C-glass gas turbine.