Absorption medium and method for removing carbon dioxide from combustion exhaust gas

An aqueous composition for removing acid gas components from a process gas, the composition comprising:

• a first cyclic amine comprising about 20 wt % to about 45 wt % of the composition, the first cyclic amine having a substituted carbon atom alpha to an amine atom;
• a second cyclic amine comprising about 5 wt % to about 15 wt % of the composition, the second cyclic amine having two unsubstituted carbon atoms, wherein each of the unsubstituted carbon atoms is alpha to an amine atom, wherein:
• the first cyclic amine and the second cyclic amine comprise substantially all of the amine content in the aqueous composition;
• and
• a water miscible solvent comprising 4 or more —O— or —OH groups.

A method of treating a process gas, the method comprising:

• providing a process gas and an aqueous absorption medium to an absorption tower;
• contacting the process gas with the aqueous absorption medium to produce a loaded aqueous absorption medium, the aqueous absorption medium comprising:
• about 20 wt % to about 45 wt % of a first cyclic amine having a substituted carbon atom alpha to an amine atom, and
• about 5 wt % to about 15 wt % of a second cyclic amine having two unsubstituted carbon atoms, wherein each of the unsubstituted carbon atoms is alpha to an amine atom, wherein:
• the first cyclic amine and the second cyclic amine comprise substantially all of the amine content in the aqueous composition;
• providing the loaded aqueous absorption medium to a regeneration tower;
• desorbing the loaded aqueous absorption medium to form a regenerated aqueous absorption medium;
• and
• recycling the regenerated aqueous absorption medium to the absorption tower.