Flue gas desulphurisation: Choices for the UK

To cut the sulfur dioxide emissions in coal-fired power stations, the Central Electricity Generating Board (CEGB) introduced its flue gas desulfurization (FGD) program. A fully integrated limestone/gypsum process is described. Furnace gas from the boiler first passes through electrostatic precipitators which remove most of the particulates and then to the FGD plant where they are quenched to remove other impurities and any remaining particulates. The gases then pass to an absorber tower where they are sprayed with a slurry of powdered limestone and water. The limestone neutralizes the sulfur dioxide and is converted to gypsum. A continuous bleed from the limestone slurry circuit is taken to a dewatering section which produces a dried crystalline gypsum.