Today, wet flue-gas desulfurization realized by spray-scrubbers represents the state of the art in the field of cleaning flue gases emitted by power plants. These systems use a sophisticated technology, yet they hit the wall when it comes to meeting extremely low limits allowed for a sub-sequent CO2 absorption which can only be achieved if a high amount of energy is used. In Niederaußem, Germany, a pilot plant was built, combining two known desulfurization systems, namely a bubble column and a conventional spray-scrubber. Prior studies on a laboratory scale suggest that this system may achieve much better removal rates without using disproportionately high amounts of energy. The purpose of this thesis is to thoroughly investigate the SO2 absorption efficiency in the pilot plant in order to find out whether the positive expectations derived from theoretical considerations are met. Alongside experiments, a calculation model was developed, which describes the measured removal rates in an analytical way. This model may provide the basis for a future scale-up of this plant. Results have shown that better desulphurization can be achieved when using the REAPlus system, instead of a conventional spray scrubber using the same amount of energy. Over longer time periods, removal efficiencies exceeding 99.5 % could be obtained.