Energy Performance of Stripper Configurations for CO2 Capture by Aqueous Amines

Aqueous absorption/stripping is the state-of-the-art technology for the capture of CO2 from coal-fired power plants. This technology is energy-intensive and has been applied to CO2 removal from natural gas, ammonia, and hydrogen gas streams. Energy requirements can be reduced by the use of a more-reactive solvent, operating the cross exchanger at a lower temperature, optimizing the stripper operation, and using innovative stripper configurations (vacuum and multipressure). This work calculates stripper performance with an algorithm in Aspen Custom Modeler (ACM) that incorporates thermodynamic studies, reaction rate measurements, physical properties, and contactor-specific information for three stripper configurations-a simple stripper operating at 160 kPa, a multipressure stripper operating at three pressures (330/230/160 kPa), and a vacuum stripper (30 kPa) for two solvents: 7m (30 wt %) monoethanolamine (MEA) and 5m K+/2.5m piperazine. The temperature approach is varied from 5 to 10° C. With some approximations, we predict the influence of using solvents with varying heats of desorption ((delta)Hdes) on the reboiler duty and the equivalent work for stripping (reboiler duty as equivalent Carnot work plus compression work). With a rich solution giving PCO2* = 2.5 kPa at 40 °C, the vacuum stripper is favored for solvents with (delta)Hdes <=21 kcal/(gmol of CO2) while the multipressure configuration is attractive for solvents with (delta)Hdes >= 21 kcal/(gmol of CO2).