Research on the Mechanism of Elemental Mercury Removal over Mn-Based SCR Catalysts by a Developed Hg-TPD Method
Using SCR catalyst to oxidize and remove elemental mercury (Hg0) synergistically is a promising method for mercury emission control in coal combustion power plants and is currently attracting widespread interest. In this study, a developed mercury thermal desorption (Hg-TPD) approach, combined with other associated methods, was employed for identification of the mercury species in the Mn-based SCR catalysts that have been used for synergistic Hg0 removal. The analysis results demonstrated the Hg0 adsorption on the catalysts was a necessary process for the Hg0 removal, though the SCR catalysts removed Hg0 mainly through catalytic oxidation and the amount of the adsorbed mercury contributed only a little to the Hg0 removal efficiency. And the essential adsorption process was mainly in the way of chemisorption. HgO was the prime species that was identified to form in the catalysts, and a little amount of adsorbed HgCl2, Hg(NO3)2 and Hg-OM was detected as well in the samples spent in the simulated coal-fired flue gases. O2, HCl, NO and high concentration of CO2 in the flue gas all promoted the adsorption capacity and the generation of related Hg compounds so that they were conductive to Hg0 removal efficiency, while similar phenomenon was not emerged in the presence of SO2, NH3 and H2O and meanwhile the amount of adsorbed HgO was decreased so that the efficiency was inhibited. The mobility testing by sequential extraction procedure indicated most of the retained Hg belonged to the mobile fraction, which was in accordance with the identification results of the Hg-TPD analysis. The consequences of this research would create a better understanding of the Hg0 removal mechanism over the Mn-based SCR catalysts and provide additional information on the disposal of the retired catalysts in the environment.
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| Format: | artículo biblioteca |
| Language: | English |
| Published: |
2019
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| Subjects: | SCR catalyst, Hg-TPD, mercury species, mobility, mechanism, |
| Online Access: | http://hdl.handle.net/10261/216506 |
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| Summary: | Using SCR catalyst to oxidize and remove elemental mercury (Hg0) synergistically is a promising method for mercury emission control in coal combustion power plants and is currently attracting widespread interest. In this study, a developed mercury thermal desorption (Hg-TPD) approach, combined with other associated methods, was employed for identification of the mercury species in the Mn-based SCR catalysts that have been used for synergistic Hg0 removal. The analysis results demonstrated the Hg0 adsorption on the catalysts was a necessary process for the Hg0 removal, though the SCR catalysts removed Hg0 mainly through catalytic oxidation and the amount of the adsorbed mercury contributed only a little to the Hg0 removal efficiency. And the essential adsorption process was mainly in the way of chemisorption. HgO was the prime species that was identified to form in the catalysts, and a little amount of adsorbed HgCl2, Hg(NO3)2 and Hg-OM was detected as well in the samples spent in the simulated coal-fired flue gases. O2, HCl, NO and high concentration of CO2 in the flue gas all promoted the adsorption capacity and the generation of related Hg compounds so that they were conductive to Hg0 removal efficiency, while similar phenomenon was not emerged in the presence of SO2, NH3 and H2O and meanwhile the amount of adsorbed HgO was decreased so that the efficiency was inhibited. The mobility testing by sequential extraction procedure indicated most of the retained Hg belonged to the mobile fraction, which was in accordance with the identification results of the Hg-TPD analysis. The consequences of this research would create a better understanding of the Hg0 removal mechanism over the Mn-based SCR catalysts and provide additional information on the disposal of the retired catalysts in the environment. |
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