Process for combined control of mercury and nitric oxide. Page: 4 of 15
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PROCESS FOR COMBINED CONTROL
OF MERCURY AND NITRIC OXIDE
Argonne National Laboratory
9700 S. Cass Avenue
Argonne, IL 60439
Continuing concern about the effects of mercury in the environment may lead to requirements for
the control of mercury emissions from coal-fired power plants. If such controls are mandated,
the use of existing flue-gas cleanup systems, such as wet scrubbers currently employed for flue-
gas desulfurization, would be desirable. Such scrubbers have been shown to be effective for
capturing oxidized forms of mercury, but cannot capture the very insoluble elemental mercury
(Hg0) that can form a significant fraction of the total emissions. At Argonne National
Laboratory, we have proposed and tested a concept for enhancing removal of Hg0, as well as
nitric oxide, through introduction of an oxidizing agent into the flue gas upstream of a scrubber,
which readily absorbs the soluble reaction products. Recently, we developed a new method for
introducing the oxidizing agent into the flue-gas stream that dramatically improved reactant
utilization. The oxidizing agent employed was NOXSORBTM, which is a commercial product
containing chloric acid and sodium chlorate. When a dilute solution of this agent was introduced
into a gas stream containing Hg0 and other typical flue-gas species at 300"F, we found that about
100% of the mercury was removed from the gas phase and recovered in process liquids. At the
same time, approximately 80% of the nitric oxide was removed. The effect of sulfur dioxide on
this process was also investigated and the results showed that it slightly decreased the amount of
Hg0 oxidized while appearing to increase the removal of nitric oxide from the gas phase. We are
currently testing the effects of variations in NOXSORBTM concentration, sulfur dioxide
concentration, nitric oxide concentration, and reaction time (residence time). Preliminary
economic projections based on the results to date indicate that the chemical cost for nitric oxide
oxidation could be less than $5,000/ton removed, while for Hg0 oxidation it would be about
Mercury was just one of many elements and compounds identified as hazardous air pollutants in
Title III of the 1990 Clean Air Act Amendments. However, it has assumed singular importance
for the electric utility industry. After studying the sources of mercury in the environment, the.
U.S. Environmental Protection Agency concluded that coal-fired boilers generate a significant
fraction (on the order of 1/3) of the total anthropogenic emissions in the U.S. Those utility
sources are widely dispersed and seem extremely dilute by typical air-pollution standards.
However, mercury can have a lifetime of many months or even years in the atmosphere and is
thus subject to long-range transport, which makes mercury control a national and international
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Livengood, C. D. & Mendelsohn, M. H. Process for combined control of mercury and nitric oxide., article, November 3, 1999; Illinois. (digital.library.unt.edu/ark:/67531/metadc707824/m1/4/: accessed September 19, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.