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Title: The Effects of Oxy-firing Conditions on Gas-phase Mercury Oxidation by Chlorine and Bromine

Abstract

Bench-scale experiments were conducted in a quartz-lined, natural gas-fired reactor with the combustion air replaced with a blend of 27 mole percent oxygen, with the balance carbon dioxide. Quench rates of 210 and 440 K/s were tested. In the absence of sulfur dioxide, the oxy-firing environment caused a remarkable increase in oxidation of mercury by chlorine. At 400 ppm chlorine (as HCl equivalent), air-firing results in roughly 5 percent oxidation. At the same conditions with oxy-firing, oxidation levels are roughly 80 percent. Oxidation levels with bromine at 25 and 50 ppm (as HBr equivalent) ranged from 80 to 95 percent and were roughly the same for oxy- and air-firing conditions. Kinetic calculations of levels of oxidation at air- and oxy-conditions captured the essential features of the experimental results but have not revealed a mechanistic basis for the oxidative benefits of oxy-firing conditions. Mixtures of 25 ppm bromine and 100 and 400 ppm chlorine gave more than 90 percent oxidation. At all conditions, the effects of quench rate were not significant. The presence of 500 ppm SO2 caused a dramatic decline in the levels of oxidation at all oxy-fired conditions examined. This effect suggests that SO2 may be preventing oxidation inmore » the gas phase or preventing oxidation in the wetconditioning system that was used in quantifying oxidized and elemental mercury concentrations. Similar effects of SO2 have been noted with air-firing. The addition of sodium thiosulfate to the hydroxide impingers that are part of wet conditioning systems may prevent liquid-phase oxidation from occurring.« less

Authors:
;
Publication Date:
Research Org.:
The University Of Utah
Sponsoring Org.:
USDOE
OSTI Identifier:
1158540
DOE Contract Number:  
NT0005015
Resource Type:
Technical Report
Country of Publication:
United States
Language:
English

Citation Formats

Buitrago, Paula, and Silcox, Geoffrey. The Effects of Oxy-firing Conditions on Gas-phase Mercury Oxidation by Chlorine and Bromine. United States: N. p., 2010. Web. doi:10.2172/1158540.
Buitrago, Paula, & Silcox, Geoffrey. The Effects of Oxy-firing Conditions on Gas-phase Mercury Oxidation by Chlorine and Bromine. United States. https://doi.org/10.2172/1158540
Buitrago, Paula, and Silcox, Geoffrey. Wed . "The Effects of Oxy-firing Conditions on Gas-phase Mercury Oxidation by Chlorine and Bromine". United States. https://doi.org/10.2172/1158540. https://www.osti.gov/servlets/purl/1158540.
@article{osti_1158540,
title = {The Effects of Oxy-firing Conditions on Gas-phase Mercury Oxidation by Chlorine and Bromine},
author = {Buitrago, Paula and Silcox, Geoffrey},
abstractNote = {Bench-scale experiments were conducted in a quartz-lined, natural gas-fired reactor with the combustion air replaced with a blend of 27 mole percent oxygen, with the balance carbon dioxide. Quench rates of 210 and 440 K/s were tested. In the absence of sulfur dioxide, the oxy-firing environment caused a remarkable increase in oxidation of mercury by chlorine. At 400 ppm chlorine (as HCl equivalent), air-firing results in roughly 5 percent oxidation. At the same conditions with oxy-firing, oxidation levels are roughly 80 percent. Oxidation levels with bromine at 25 and 50 ppm (as HBr equivalent) ranged from 80 to 95 percent and were roughly the same for oxy- and air-firing conditions. Kinetic calculations of levels of oxidation at air- and oxy-conditions captured the essential features of the experimental results but have not revealed a mechanistic basis for the oxidative benefits of oxy-firing conditions. Mixtures of 25 ppm bromine and 100 and 400 ppm chlorine gave more than 90 percent oxidation. At all conditions, the effects of quench rate were not significant. The presence of 500 ppm SO2 caused a dramatic decline in the levels of oxidation at all oxy-fired conditions examined. This effect suggests that SO2 may be preventing oxidation in the gas phase or preventing oxidation in the wetconditioning system that was used in quantifying oxidized and elemental mercury concentrations. Similar effects of SO2 have been noted with air-firing. The addition of sodium thiosulfate to the hydroxide impingers that are part of wet conditioning systems may prevent liquid-phase oxidation from occurring.},
doi = {10.2172/1158540},
url = {https://www.osti.gov/biblio/1158540}, journal = {},
number = ,
volume = ,
place = {United States},
year = {2010},
month = {6}
}