Understanding the Impact of Process Design on the Cost of CO2 Capture for Precipitating Solvent Absorption

There has been increasing interest in the development of solvents for CO2 capture including solvents that involve precipitation during CO2 absorption. On the basis of Le Chatelier's principle, the CO2 absorption equilibrium can be shifted by removing one of the reaction products, resulting in a higher absorption capacity. Two phase-change solvents are investigated: promoted potassium carbonate (where the CO2 is incorporated in the solid phase) and potassium taurate (where the CO2 is incorporated in the liquid phase). A high-level assessment is performed with the two phase-change solvents in order to identify key areas in solvent system design for possible cost reduction. The impacts of absorption contactor type, the addition of a solid liquid separator, and heat integration opportunities on capture cost and total heat duty are investigated. For both phase-change solvents, the lowest capture cost is found when the CO2 absorption is operated in a packed column and advanced heat exchanger integration is used in which the dissolution heat exchanger duty is supplied without consuming low pressure (LP) steam for the power plant. For the cases investigated, there is little difference in capture cost between the two phase-change solvents.