Carbon dioxide (CO₂) is a major Greenhouse gas responsible for global warming, and hence, substantial effort is being put on the development of technologies for its capture from process gas streams. Integrating amine scrubbers into a power plant would increase the energy requirement by 25-40% [1]. Nevertheless, amine scrubbing appears to be most suitable and will probably remain the dominating technology for CO₂ capture from coal-fired power plants in 2030 [2]. Many amine-based solvents (e.g., amine blends, activated amines, sterically hindered amine) are reported to be advantageous with respect to reduced energy consumption, but they have not yet been evaluated as solvents for application at real power plants.

In this study, promising amine-based solvents reported in the open literature were numerically investigated as candidate absorbents for efficient CO₂ capture in absorption-stripping loops. The main focus was to determine the optimal working conditions in terms of energy consumption and to carry out a fair comparison with the commonly used monoethanolamine based CO₂ capturing process. In order to compare different solvents at real conditions, one gas and one coal fired power plant were chosen as example flue gas sources. The CO₂ concentration was 3 to 5 mol% for the gas-fired case and 12 to 16 mol% for the coal-fired case.

The numerical investigations were performed based on the model developed in an earlier work [3]. This rate-based model is capable of describing the complex interactions of chemical reactions, heat transfer and multicomponent mass transfer in a rigorous way. It accounts for thermodynamic non-idealities and covers the specific behaviour of electrolyte solutions. The influence of column internals and hydraulics is considered through relevant correlations. The model is implemented into the commercial software Aspen Custom Modeler®, while physical properties are determined with the help of the software package Aspen Properties®. Along these lines, rigorous simulation of absorption and stripping units becomes possible.

The results of the numerical studies performed in this work help to identify optimal solvents for CO₂ capture avoiding using lengthy and expensive pilot-plant experiments.

 [1]         D.M. D’Alessandro, B. Smit and J.R. Long, Carbon dioxide capture: Prospects for new materials, Angew. Chem. Int. Ed. 49 (2010) 6058-6082.

[2]          G.T. Rochelle, Amine scrubbing for CO₂ capture, Science 325 (2009) 1652-1654.

[3]          B. Huepen and E.Y. Kenig, Rigorous modeling and simulation of an absorption-stripping loop for the removal of acid gases, Ind. Eng. Chem. Res. 49 (2010) 772-779.