Flue-gas desulfurization (FGD) is the removal process of sulfur dioxide (SO 2 ) from flue gas emissions, often chemically. Sulfur dioxide in gases is produced by the combustion of fossil fuels and many industrial processes such as gasoline refining as well as cement, paper, glass, steel, iron and copper production. Sulfur dioxide emissions are a primary contributor to acid rain and have been regulated by every industrialized nation in the world.
FGD processes vary depending on the amount of SO 2 involved, the solution being used to absorb the SO 2 , and the particular equipment used in the absorption tower.
Methods of removing sulfur dioxide from boiler and furnace exhaust gases have been studied for over 150 years. Early ideas for flue gas desulfurization were established in England around 1850.With the construction of large-scale power plants in England in the 1920s, the problems associated with large volumes of SO
2 from a single site began to concern the public. The SO
2 emissions problem did not receive much attention until 1929, when the House of Lords upheld the claim of a landowner against the Barton Electricity Works of the Manchester Corporation for damages to his land resulting from SO
2 emissions. Shortly thereafter, a press campaign was launched against the erection of power plants within the confines of London. This outcry led to the imposition of SO
2 controls on all such power plants.
The first major FGD unit at a utility was installed in 1931 at Battersea Power Station , owned by London Power Company . In 1935, an FGD system similar to that installed at Battersea went into service at Swansea Power Station. The third major FGD system was installed in 1938 at Fulham Power Station . These three early large-scale FGD installations were abandoned during World War II . Large-scale FGD units did not reappear at utilities until the 1970s, where most of the installations occurred in the United States and Japan .
As of June 1973, there were 42 FGD units in operation, 36 in Japan and 6 in the United States, ranging in capacity from 5 MW to 250 MW. As of around 1999 and 2000, FGD units were being used in 27 countries, and there were 678 FGD units operating at a total power plant capacity of about 229 gigawatts . About 45% of the FGD capacity was in the US, 24% in Germany , 11% in Japan, and 20% in various other countries. Approximately 79% of the units, representing about 199 gigawatts of capacity, were using lime or limestone wet scrubbing. About 18% (or 25 gigawatts) utilized spray-dry scrubbers or sorbent injection systems