Stripping acid gas back out of rich amine so the solvent returns to the contactor without degrading.
The regenerator is the return leg of the amine loop. Rich solvent is heated and steam-stripped so the acid gas is driven off and lean amine can go back to the contactor. Reboiler duty here is usually the largest energy consumer on the unit.
The design tension is between stripping hard enough to get a low lean loading, and running hot enough for long enough to thermally degrade the amine. Internals that improve contact let you hit lean spec at lower reboiler duty, which saves both energy and solvent.
