Flue-gas desulfurization (FGD) is a set of technologies used to remove sulfur dioxide (SO2) from exhaust flue gases of fossil-fuel power plants, steel company etc, and from the emissions of other sulfur oxide emitting processes. Limestone-gypsum desulfurization process is one of the most widely used desulfurization technologies in the world. About 90% thermal power plants in Japan, Germany, and the United States adopted this technology for the flue gas desulfurization.