Analysis of Process Configurations for CO₂ Capture by Precipitating Amino Acid Solvents

Abstract

Precipitating amino acid solvents are an alternative to conventional amine scrubbing for CO 2 capture from flue gas. Process operation with these solvents leads to the formation of precipitates during absorption that need to be re-dissolved prior to desorption of CO 2 . The process configuration is crucial for the successful application of these solvents. Different process configurations have been analyzed in this work, including a full analysis of the baseline operating conditions (based on potassium taurate), the addition of lean vapor compression, multiple absorber feeds, and the use of different amino acids as alternative solvents to the baseline based on potassium taurate. The analysis is carried out with an equilibrium model of the process that approximates the thermodynamics of the solvents considered. The results show that the precipitating amino acid solvents can reduce the reboiler duty needed to regenerate the solvent with respect to a conventional MEA process. However, this reduction is accompanied by an expenditure in lower grade energy needed to dissolve the precipitates. To successfully implement these processes into power plants, an internal recycle of the rich stream is necessary. This configuration, known as DECAB Plus, can lower the overall energy use of the capture process, which includes the energy needed to regenerate the solvent, the energy needed to dissolve the precipitates, and the energy needed to compress the CO 2 to 110 bar. With respect to the energy efficiency, the DECAB Plus with lean vapor compression configuration is the best configuration based on potassium taurate, which reduces the reboiler duty for regeneration by 45% with respect to conventional MEA. Retrofitting this process into a coal fired power plant will result in overall energy savings of 15% with respect to the conventional MEA process, including compression of the CO 2 stream to 110 bar. Potassium alanate was found to reduce the energy use with respect to potassium taurate under similar process configurations. Therefore, the investigation of potassium alanate in a DECAB Plus configuration is highly recommended, since it can reduce the energy requirements of the best process configuration based on potassium taurate.

Energy-Efficient CO2 Capture from Flue Gas by Absorption with Amino Acids and Crystallization with a Bis-Iminoguanidine

“…An improved CO2 capture process based on precipitating amino acid sorbents has been recently proposed. 6,7 The regeneration energy for this process, estimated from conceptual design models, was found to be 35% lower than for the MEA benchmark (excluding the energy required to redissolve the precipitates). 6 A recent techno-economic analysis of CO2 capture involving precipitating solvents found lower regeneration energies and costs for such phasechanging processes.…”

Useful Mechanisms, Energy Efficiency Benefits, and Challenges of Emerging Innovative Advanced Solvent Based Capture Processes

“…Thus using energy efficiency techniques such as flash and lean vapour compression a further decrease of the energy requirement can be obtained, e.g. to 1900 kJ/kgCO 2 as shown in [15].…”

Absorption of CO2 in aqueous blend of methyldiethanolamine and arginine

“…The positive charge is delocalized, enabling the formation of multiple hydrogen bonds because the double bond and the nitrogen lone pairs are coupled. This nature makes Arg a good solvent for carbon dioxide 28 . The absorption and desorption of CO 2 by Arg blended with K 2 CO 3 solvent were previously proposed and showed promising results 3 .…”