Process for combined control of mercury and nitric oxide.
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 (Hg{sup 0}) 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 Hg{sup 0}, 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 NOXSORB{trademark}, 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 Hg{sup 0} 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 Hg{sup 0} oxidized while appearing to increase the removal of nitric oxide from the gas phase. We are currently testing the effects of variations in NOXSORB{trademark} 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 $$5,000/ton removed, while for Hg{sup 0} oxidation it would be about $$20,000/lb removed.
- Research Organization:
- Argonne National Lab., IL (US)
- Sponsoring Organization:
- US Department of Energy (US)
- DOE Contract Number:
- W-31-109-ENG-38
- OSTI ID:
- 750449
- Report Number(s):
- ANL/ES/CP-98498; TRN: US200221%%306
- Resource Relation:
- Conference: 1999 EPRI-DOE-EPA Combined Utility Air Pollutant Control Symposium, Atlanta, GA (US), 08/16/1999--08/20/1999; Other Information: PBD: 3 Nov 1999
- Country of Publication:
- United States
- Language:
- English
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