What is Flue Gas Desulfurization (FGD)?
Flue gas desulfurization is a chemical process to remove sulfur oxides from the flue gas at coal-burning power plants. Many FGD methods have been developed to varying stages of applicability. Their goal is to chemically combine the sulfur gases released in coal combustion by reacting them with a sorbent, such as limestone (calcium carbonate, CaCO3), lime (calcium oxide, CaO) or ammonia (NH3). Of the FGD systems in the United States, 90 percent use limestone or lime as the sorbent. As the flue gas comes in contact with the slurry of calcium salts, sulfur dioxide (SO2) reacts with the calcium to form hydrous calcium sulfate (CaSO42H20) or gypsum.
