Stripper Configurations for CO2 Capture by Aqueous Amines

A monumental task for improving the feasibility of carbon capture from the flue gas of coal-fired power plants is reducing the total energy cost. A generic absorption/stripping process using an aqueous amine solvent would reduce the net power production of a coal-fired power plant by roughly 30%, but advanced stripper configurations can help cut down on the lost power. In this work a variety of configurations was evaluated to quantify the benefit of complex flowsheets. These flowsheets utilized one or more of the following: equilibrium flashes and/or packed sections, multiple pressure levels, and vapor recompression. The flowsheets were evaluated for 9 m (35wt%) MEA using the E-NRTL method in Aspen Plus® and a previous thermodynamic model constructed by Hilliard.

Performance was evaluated by an equivalent work value, calculated from the pump work, compressor work, and calculated extractable electrical work from the steam used for heating. When considering the optimum lean loading of each configuration, only the 1-stage flash exhibited a higher equivalent work than the simple stripper base case, and all other configurations showed an improvement. At the ceiling temperature for MEA due to thermal degradation, 120°C, the double matrix configuration with packing performed best, requiring 33.4 kJ/mol CO₂ compared to 35.0 kJ/mol CO₂ for the simple stripper. Improving reversibility in the stripper had a large impact on its performance, and better reversibility was attained by reducing driving forces throughout the flowsheet.