17 Ammonia Injection: A Route to Clean
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Stacks C. C. S H A L E Morgantown Energy Research Center, Bureau of Mines, U.S. Department of the Interior, P.O. Box 880, Morgantown, W . Va. 26505
Previously reported results of laboratory research have demonstrated essentially complete removal of sulfur dioxide from mixed gases by ammonia injection; the simulated stack gas contained 4200 ppm of the contaminant which is equivalent to combustion of coal containing 6.0% sulfur. Continuation of this work using gases from a small coal-fired combustor confirms earlier findings for removal of sulfur dioxide to less than 100 ppm and shows that ammonia can be regenerated on a continuous basis for re-use with minimal loss. Product sulfur-bearing salts and remaining ash are removed effectively from the gas in a wet scrubber, apparently assisted by the process of nucleation. The ammonia-injection process could provide effective control of sulfur dioxide from coal-burning power plants.
eduction in S 0 emissions from coal-burning power plant stacks is ^ essential to minimize atmospheric pollution from this source. Projections of energy demand show that by 1980 coal will account for about 25 million tons of total sulfur oxides output, mostly S0 , unless effective control methods are developed. A vapor-phase ammmonia-injection process for S 0 removal is being developed at the Morgantown Energy Research Center. In laboratory research with simulated stack gas containing 4200 ppm S 0 (equivalent to 6.0% sulfur in coal), essentially complete removal of S 0 from the gas phase was effected by ammonia injection (J). Preliminary work has since proceeded with a small pilot-scale installation in which the sulfur products from the vapor-phase reaction are removed in a water scrubber. This paper presents additional data from the laboratory work and the pilot-scale installation. 2
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195 Jimeson and Spindt; Pollution Control and Energy Needs Advances in Chemistry; American Chemical Society: Washington, DC, 1974.
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POLLUTION CONTROL AND ENERGY NEEDS
Description of Process In the vapor-phase ammonia-injection process, water (or steam) and gaseous ammonia are injected into the stack gas while the gas is at some temperature ( > 1 6 0 ° F ) above the decomposition temperature of ammonium sulfite, the principal product (140° to 1 5 8 ° F ) (2). After the water is vaporized and the reactants are thoroughly mixed, the gas is cooled below 140 ° F and the finely divided salt particles separate from the gas as a smoke or fume (d = 0.01-1.0/im). The entrained solids, salt particles, andflyash are then recovered concurrently. p
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