The purpose of flotation is to remove contaminants such as ink, stickies and wax from the stock suspension. Fillers and coating particles can also be removed efficiently by flotation.
In most cases, the unit is arranged as a 2-stage flotation system. The overflow from the primary stage is reflated in the secondary stage. The task of the primary stage is to produce the required optical quality of the accepts. The secondary stage minimizes overall losses and removes the undesired particles from the system. Fibers recovered from the primary overflow are fed back into the main circuit, together with the secondary accepts, which either flow backward or forward. In the 2-stage layout, the flotation process attains maximum efficiency.