Flue-gas desulfurization

Flue-gas desulfurization removes sulfur dioxide from exhaust gases produced by burning sulfur-containing fuels, usually by absorbing it into a reagent and converting it into a solid product.

Wet limestone-gypsum flue-gas desulfurization: A process that absorbs sulfur dioxide in a limestone slurry and oxidizes the resulting sulfite into gypsum. This widely used wet process illustrates how an absorbent becomes a saleable solid byproduct.
Dry sorbent injection: A pollution-control method that injects dry alkaline sorbent into exhaust to capture acidic gases. It avoids slurry scrubbers but generally captures less sulfur dioxide per unit of reagent.
Coal-fired power station: A power plant that burns coal to produce steam and generate electricity. Coal combustion releases sulfur dioxide, making these plants a major setting for desulfurization.
Clean Air Act: A United States federal law that regulates air emissions from stationary and mobile sources. Its amendments drove major reductions in power-plant sulfur dioxide emissions and widespread scrubber installation.
Flue-gas desulfurization wastewater treatment: Treatment processes that remove contaminants from wastewater produced by wet flue-gas desulfurization. Managing dissolved metals and salts remains a significant challenge for wet scrubber systems.
Spray-dry scrubber: An air-pollution control device that sprays alkaline slurry into hot exhaust, where it dries after reacting with acidic gases. It captures sulfur dioxide with less water and produces dry waste rather than gypsum slurry.
Seawater flue-gas desulfurization: A process that uses seawater alkalinity to absorb sulfur dioxide and oxidize it before discharge. It replaces limestone reagent with seawater, making it suitable mainly for coastal plants.
Industrial flue gas: Exhaust gas from industrial processes or fuel combustion, containing combustion products and process-specific pollutants. Desulfurization also treats sulfur dioxide from industrial furnaces and processing plants.
Acid deposition: The transfer of acidic compounds from the atmosphere to Earth’s surface through wet or dry processes. Desulfurization reduces sulfur emissions that contribute to acidic deposition.
Mercury emissions from coal-fired power plants: Mercury released when coal is burned and carried in power-plant flue gas or residues. Scrubber chemistry can affect mercury capture, but sulfur removal alone does not guarantee adequate control.

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