Evaporation of Purge Water from Wet FGD Scrubbers

摘要

In coal-fired power stations, flue-gas desulfurization (FGD) is employed to "scrub" most of the sulfur dioxide, SO_2, from the flue-gas. FGD is often performed by means of a wet process in which SO_2 is absorbed from the flue-gas by spraying it with a slurry containing limestone (mainly calcium carbonate, CaCO_3). The SO_2 reacts to form calcium sulfite, CaSO_3, which is further oxidized to produce gypsum (CaSO_4·2H_2O) by introducing air into the scrubber. The gypsum product is often washed and sold for a variety of uses or may be disposed of in a landfill. In the USA and the European Union, wet scrubbing is installed on more than 80% of the coal-fired power plants and is considered to be best available technology for SO_2 removal.