The flexibility of absorption and distillation columns is limited by macroscopic fluid dynamic phenomena like flooding, entrainment, weeping or dewetting. The design of those columns is a crucial task and depends on the separation task, the needed capacity and the fluid dynamic boundaries. An enhancement in flexibility is necessary to face upcoming challenges in chemical industry, including increasing uncertainties in material and energy supply or product demand. Results show that an increased flexibility is either possible by means of internal structuring or modularization of the columns. Both measures have a potential to enhance capacity flexibility of absorption and distillation columns.