Innovative Absorber/Stripper Configurations for CO2 Capture by Aqueous Monoethanolamine

The state-of-the-art technology to capture CO2 from coal-fired power plants is absorption/stripping with aqueous monoethanolamine (MEA). The energy consumption in stripping can be 15-30% of the power-plant output. A rigorous rate-based model for CO2-MEA-H2O was used to simulate several flowsheet alternatives that reduce the energy requirement using Aspen Plus with RateFrac. Results were calculated for vapor recompression, multipressure, and simple strippers at 5 and 10° C approach temperatures and 70, 90, and 95% CO2 removal. The "equivalent work of steam/mole of CO2 removed" and the reboiler duty were used to compare the proposed schemes and to show the shift of energy use from work to heat. The total equivalent work for multipressure was less than that for the simple stripper by 0.03-0.12 GJ/(ton of CO2), and the reboiler duty was less by 0.15-0.41 GJ/(ton of CO2). The multipressure with vapor recompression is an attractive option because it utilizes the overhead water vapor latent heat to reduce reboiler duty load, recovers the work of compression to strip more CO2, and shows more reversible behavior.