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Flue Gas Desulfurization Material

Photo of Flue Gas Desulfurization (FGD) Material
Courtesy of the American Coal Ash Association

Flue Gas Desulfurization (FGD) Material is a product of a process typically used for reducing SO2 emissions from the exhaust gas system of a coal-fired boiler. The physical nature of these materials varies from a wet sludge to a dry powdered material depending on the process. The wet sludge from a lime-based reagent wet scrubbing process is predominantly calcium sulfite. The wet product from limestone based reagent wet scrubbing processes is predominantly calcium sulfate. The dry material from dry scrubbers that is captured in a baghouse consists of a mixture of sulfites and sulfates. This powdered material is referred to as dry FGD ash, dry FGD Material, or lime spray dryer ash. FGD gypsum consists of small, fine particles.

Calcium sulfite FGD material can be used as an embankment and road base material. Calcium sulfate FGD material, once it has been dewatered, can be used in wallboard manufacturing and in place of gypsum for the production of cement. The largest single market for FGD material is in wallboard manufacturing.

FGD material applications include its use as a:

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