In the flue gas desulphurisation systems of the hard coal-fired power plants, the sulphur-dioxide present in the flue gas reacts with natural lime. The subsequent oxidation of the reaction products results in the creation of FGD gypsum whose chemical composition in no way differs to that of natural gypsum. Similarly to natural gypsum, it is used for the production of plasterboards, gypsum plaster, filling compounds, as a binding agent for mortars and as a setting agent in cement.