The invention relates to an aeration system for seawater oxidation in flue gas purification devices, with at least one tubular diffuser (TD), covered by at least two perforated membranes (20), which are positioned one after the other and at a distance to each other in a direction of the central longitudinal axis (A) of the diffuser (TD) as well as at least one support member (SP), which encircles a membrane-free section (FS) of the tubular diffuser at least partially, and at least one sliding means (40), arranged between the support member (SP) and the membrane-free section (FS) of the tubular diffuser (TD).