Flue-Gas-Desulfurization Waste

If coal or oil is the fuel source, the FGD control technologies result in the generation of solid wastes. Wet lime/limestone scrubbers produce a slurry of ash, unreacted lime, calcium sulfate, and calcium sulfite. Dry scrubber systems produce a mixture of unreacted sorbent (e.g., lime, limestone, sodium carbonates, and calcium carbonates), sulfur salts, and fly ash. 

Sludge is typically stabilized with fly ash and sludge produced in a wet scrubber may be disposed of in impoundments or below-grade landfills, or may be stabilized and disposed of in landfills. Dry scrubber sludge may be managed dry or wet. 

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Flue gas desulfurization wastes, other inorganic wastes... 

Flue gas desulfurization wastes, other wastes with large proportions of calcium sulfate or calcium sulfite... 

Goodwin, R. W., "Oxidation of Flue Gas Desulfurization Waste and the Effect on Treatment Modes," J. Air Pollution Control Assn, 28, 35 (1978). 

Particle size distribution relating to gas cleaning is well understood in the industry. This section deals with general rules of thumb. Certain important issues not included in this section are flue gas desulfurization, flue gas denitrification, hazardous waste gas cleaning, waste incineration gas cleaning, and removal of CO2 from flue gas. All these topics have special requirements, which must be considered separately in the design process. 

Calcilox A process for converting calcium sulfate/sulfite wastes from flue-gas desulfurization into a disposable, earthy material, by use of a proprietary inorganic additive made from blast furnace slag. Developed by Dravo Corporation of Pittsburgh, PA. 

Howden An early flue-gas desulfurization process using a lime or chalk slurry in wooden grid-packed towers. The calcium sulfate/sulfite waste product was intended for use in cement manufacture, but this was never commercialized. The key to the process was the use of a large excess of calcium sulfate in suspension in the scrubbing circuit, which minimized the deposition of scale on the equipment. The process was developed by Imperial Chemical Industries and James Howden Company in the 1930s and operated for several years at power stations at Fulham, London, and Tir John, South Wales, being finally abandoned during World War II. British Patents 420,539 433,039. 

NEUTREC A flue-gas desulfurization process, intended for treating the waste gases from incinerators for municipal, hospital, and industrial wastes. Sodium bicarbonate, optionally mixed with active carbon, is injected into the gases after the usual bag filter, and the solid products are removed in a second bag filter. Sodium compounds can be recovered from the product for reuse, and ary toxic compounds disposed of separately. Developed by Solvay and operated in Europe since 1991. 

Terra-Crete A process for stabilizing the calcium sulfate/sulfite waste from flue-gas desulfurization, so that it may be used for landfill. Calcination converts the calcium sulfite to cementitious material to which proprietary additions are made. Developed by SFT Corporation, York, PA. See also Terra-Tite. 

Many such developments have recently been carried out in the fields of municipal wastes,metal-bearing fines, by-products from flue gas desulfurization,and dust or ashes from waste incineratorsProducts may be fertilizers, arc furnace feed, artificial lump gypsum, or aggregate. 

Many industrial processes rely on effective agitation and mixing of fluids. The application of agitators cover the areas of mining, hydrometallurgy, biol-ogy, petroleum, food, pulp and paper, pharmaceutical and chemical process industry. In particular, in these industries we find typical chemical reaction engineering processes like fermentation, waste water treatment, hydrogenation, polymerization, crystallization, flue gas desulfurization, etc [65, 21]. 

Lime/limestone slurry scrubbing is the dominant commercial technology for flue gas desulfurization 0.). SO2 is absorbed at 50-55°C and pH 5.5-6.0 in an aqueous slurry of excess CaC03 and product solids. The CaS03/CaS04 product is disposed of as solid waste. With greater than 500-1000 ppm SO2 in the flue gas, SO2 absorption is controlled by liquid-film mass transfer resistance because of the limited solubility of SO2 gas and alkaline solids. Additives that buffer between pH 3 and pH 5.5 enhance S02 absorption by providing dissolved alkaline species for reaction with SO2 (8). 

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