Systems Analysis of SO2-CO2 Co-Capture from a Post-Combustion Coal-Fired Power Plant in Deep Eutectic Solvents

In this study, CO2 and SO2 captures from post-combustion flue gas from a pulverized coal-fired power plant were evaluated using deep eutectic solvents (DES) to replace existing mono-ethanol amine (MEA) and CanSolv technologies. The system design of the DES-based CO2 and SO2 capture was based on the National Energy Technology Laboratory's (NETL) 550 MWe pulverized coal-fired power plant model using Illinois #06 coal. Two of the most studied DES (choline chloride and urea at a 1:2 molar ratio and methyltriphenylphosphonium bromide (METPB) and ethylene glycol at a 1:3 molar ratio) for CO2 and SO2 capture were evaluated for this system analysis. Physical properties of DES were evaluated using both density functional theory (DFT)-based modeling as well as with documented properties from the literature. A technoeconomic assessment (TEA) was completed to assess DES ability to capture CO2 and SO2. Both solvents were able to fully dissolve and capture all SO2 present in the flue gas. It was also found from the system analyses that choline chloride and urea outperformed METPB and ethylene glycol (had a lower final cost) when assessed at 10-30% CO2 capture at high operating pressures (greater than 10 bar). At high system sizes (flow rate of greater than 50,000 kmoles DES per hour), choline chloride:urea was more cost effective than METPB:ethylene glycol. This study also establishes a modeling framework to evaluate future DES for physical absorption systems by both thermophysical and economic objectives. This framework can be used to greatly expedite DES candidate screening in future studies.