Coal also contains small amounts of sulfur. During the combustion process in the boiler this sulfur is oxidized, forming sulfur dioxide. In the flue gas desulfurization plant (FGD plant for short) the sulfur dioxide is removed from the flue gas by a chemical process. This happens in the so-called scrubber. In the scrubber the flue gas is directed upwards; simultaneously, lime dissolved in water is sprayed from above into the scrubber. This lime slurry binds the sulfur dioxide. The reaction gives rise to gypsum, which is used in the construction industry.