Operating the CO2 absorption plant in a post-combustion unit in flexible mode for cost reduction

Carbon dioxide greatly contributes to climate change and its emissions must be limited. Combustion of fossil fuels in power plants to produce electricity generates the largest amount of CO2 released into the atmosphere, therefore application of Carbon Capture and Storage (CCS) to this sector would help in reducing the emissions of this acid gas. CO2 absorption with aqueous amines is the most common capture technology for post-combustion CO2 removal and is characterized by high energy requirements, mainly for CO2 release from the solvent and compression of the obtained rich-CO2 stream. For this reason operating the CCS system in a power plant significantly reduces the power output and, consequently, the revenues from selling electricity. In order to deal with this issue while maintaining low carbon dioxide emissions, flexible operation may be applied. In this work, a detailed analysis of the application of the solvent storage mode for flexible operation of the CO2 removal section of a natural gas combined cycle power plant has been performed. Simulations in ASPEN Plus®, properly customized for the description of the system, and a techno-economic model created by the GASP group of Politecnico di Milano have been run to find the best solution. The variation of price of electricity from hour to hour for key days and for the overall year have been considered. Different values of carbon tax to be applied have been also taken into account.