Precipitating Amino Acid Solvents for CO2 Capture. Opportunities to Reduce Costs in Post Combustion Capture.

Abstract

Post-combustion CO2 capture based on absorption and thermal desorption is considered a suitable technology for carbon abatement in fossil fuelled power plants. The economic viability of post-combustion capture has been widely studied. The major drawbacks of this technology are the efficiency penalties and high operating cost related to solvent regeneration and CO2 compression, and the potential emission of harmful solvent components. Precipitating amino acid solvents are an alternative to conventional amine scrubbing for CO2 capture from flue gas. These solvents are non-volatile and less toxic than conventional amines. Therefore, the environmental risk related to the emissions of solvent is drastically reduced. Nevertheless, the capture operation with these solvents leads to the formation of precipitates during absorption, which need to be handled in a controlled manner to successfully design a viable process. This work evaluates the technical feasibility of process configurations that contribute to reduce the overall energy use of capture processes based on precipitating amino acid solvents. The process configurations are based on absorption and desorption enhancement effects that are directly or indirectly related to precipitation. The conceptual design of new processes (DECAB and DECAB Plus) based on aqueous solutions of potassium taurate and potassium alanate is described and used to evaluate the performance of these processes. The design is supported by experimental data previously published in the literature. The integration of these process concepts into a coal fired power plant has been evaluated by process simulation of the steam cycle with Aspen Plus ® combined with the capture process requirements estimated by an equilibrium model of the capture process that approximates the thermodynamics of the solvents considered. The DECAB Plus configuration has a net beneficial impact on the energy use of the capture process. The best configuration studied is the DECAB Plus with LVC, which provides up to 4% more power output than the MEA baseline with LVC.