Revisions in 1990 to the Clean Air Act require additional reductions to sulfur dioxide this year and the year 2000. Coal fired power plants targeted for compliance this year are located in Alabama, Florida, Georgia, Illinois, Indiana, Iowa, Kansas, Kentucky, Maryland, Michigan, Minnesota, Mississippi, Missouri, New Hampshire, New Jersey, New York, Ohio, Pennsylvania, Tennessee, West Virginia and Wisconsin. The process involves spraying a limestone slurry into the gas stream before it is released into the environment. The slurry attaches to sulfur, and the newly formed compound is removed for disposal or sold as a recycled by-product. The answer for many existing coal burning power plants and industrial boilers may be limestone injection.
Limestone is introduced into the boiler, either at the point of combustion or immediately after.
SO2 can also be removed by injecting lime into the flue gas duct. A limestone and lime injection installation does not require the great amount of physical space that a scrubber does. CFBC is a process that removes sulfur from coal during combustion. In a fluidized bed boiler, crushed coal and limestone are suspended in the bottom of a boiler by an upward stream of hot air. As coal burns, sulfur gases from the coal combine with limestone to form a solid compound that is recovered with ash.