Flexibility and Efficiency of Steam Turbine Extraction vs Gas Fired Generation as Steam Source for Post Combustion CO2 Capture on Coal Fired Power Plant

Abstract

CO2 emissions from electrical power generation must be reduced if global climate change mitigation targets are to be met. Expansion of renewable sources of power generation and the application of carbon capture and sequestration are two strategies required to reduce the CO2 emissions from this sector. As the penetration of renewable resources increases, non-renewable generation will need to become more flexible in order to back-up the intermittent renewable energy sources. Post combustion CO2 capture is the only proven full scale option currently available for reducing emissions from existing coal fired power plants. Post combustion capture processes however require significant quantities of thermal energy (or steam) to regenerate the solvent used for CO2 capture. This requirement for thermal energy can represent almost half of the de-rate associated with CO2 capture. Numerous studies have evaluated sources of this thermal energy; such as the existing steam turbine, or the integration of new gas fired sources. Most studies that have compared these sources of thermal energy have evaluated only performance at full load but this study focuses on flexibility and efficiency of these two configurations over a broader range of output. The conclusion of the study is that the existing steam turbine of the associated power plant can be re-engineered to become a more efficient and a more flexible source of the thermal energy than the addition of a gas fired generation source.