Capture columns handle flue gas volumes far beyond typical process plant, at close to atmospheric pressure. The driving force for absorption is low, so the columns are tall and wide — and every millibar of resistance across the packing turns directly into fan energy for the life of the plant.

Liquid distribution becomes disproportionately important at these diameters. A bed that is unevenly irrigated wastes both the packing height and the energy spent pushing gas through it, so distributor design carries more weight here than almost anywhere else.