Mercury Speciation and Distribution in a 660-Megawatt Utility Boiler in Taiwan Firing Bituminous Coals

Hsi, Hsing‐Cheng; Lee, Hsiu-Hsia; Hwang, J.Y.; Chen, Wang

doi:10.3155/1047-3289.60.5.514

Cited by 28 publications

(6 citation statements)

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“…Stack data, however, indicate a large variability of the mercury species ratios between CFPPs, depending on multiple parameters such as air pollution control devices (APCD) used and the mercury content of coal burned at a given time (Hsi et al, 2010). Such variations are not accounted for in inventories.…”

Section: Emission Uncertaintiesmentioning

confidence: 99%

Evaluation of discrepancy between measured and modelled oxidized mercury species

et al. 2013

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Abstract. L. Zhang et al. (2012), in a recent report, compared model estimates with new observations of oxidized and particulate mercury species (Hg2+ and Hgp) in the Great Lakes region and found that the sum of Hg2+ and Hgp varied between a factor of 2 to 10 between measurements and model. They suggested too high emission inputs as Hg2+ and too fast oxidative conversion of Hg0 to Hg2+ and Hgp as possible causes. This study quantitatively explores measurement uncertainties in detail. These include sampling efficiency, composition of sample, interfering species and calibration errors. Model (Global/Regional Atmospheric Heavy Metals Model – GRAHM) sensitivity experiments are used to examine the consistency between various Hg measurements and speciation of Hg near emission sources to better understand the discrepancies between modelled and measured concentrations of Hg2+ and Hgp. We find that the ratio of Hg0, Hg2+ and Hgp in the emission inventories, measurements of surface air concentrations of oxidized Hg and measurements of wet deposition are currently inconsistent with each other in the vicinity of emission sources. Current speciation of Hg emissions suggests higher concentrations of Hg2+ in air and in precipitation near emission sources; however, measured air concentrations of Hg2+ and measured concentrations of Hg in precipitation are not found to be significantly elevated near emission sources compared to the remote regions. The averaged unbiased root mean square error (RMSE) between simulated and observed concentrations of Hg2+ is found to be reduced by 42% and for Hgp reduced by 40% for 21 North American sites investigated, when a ratio for Hg0 : Hg2+ : Hgp in the emissions is changed from 50 : 40 : 10 (as specified in the original inventories) to 90 : 8 : 2. Unbiased RMSE reductions near emissions sources in the eastern United States and Canada are found to be reduced by up to 58% for Hg2+. Significant improvement in the model simulated spatial distribution of wet deposition of mercury in North America is noticed with the modified Hg emission speciation. Measurement-related uncertainties leading to lower estimation of Hg2+ concentrations are 86%. Uncertainties yielding either to higher or lower Hg2+ concentrations are found to be 36%. Finally, anthropogenic emission uncertainties are 106% for Hg2+. Thus it appears that the identified uncertainties for model estimates related to mercury speciation near sources, uncertainties in measurement methodology and uncertainties in emissions can close the gap between modelled and observed estimates of oxidized mercury found in L. Zhang et al. (2012). Model sensitivity simulations show that the measured concentrations of oxidized mercury, in general, are too low to be consistent with measured wet deposition fluxes in North America. Better emission inventories (with respect to speciation), better techniques for measurements of oxidized species and knowledge of mercury reduction reactions in different environments (including in-plume) in all phases are needed for improving the mercury models.

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Section: Emission Uncertaintiesmentioning

confidence: 99%

Evaluation of discrepancy between measured and modelled oxidized mercury species

et al. 2013

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“…Coal-fired power plants were reported as the largest single source in most countries in Hg emissions (Pacyna et al, 2010). Hg is present in the coal-combustion flue gases in three major forms, namely, particle-bound (Hg p ), oxidized (Hg 2+ ), and elemental (Hg 0 ) forms (Hsi et al, 2010;Wilcox et al, 2012). Hg p and Hg 2+ can be readily captured by traditional air pollution control devices, such as electrostatic precipitators and wet flue gas desulfurization.…”

Section: Introductionmentioning

confidence: 99%

Influences of Copper(II) Chloride Impregnation on Activated Carbon for Low-Concentration Elemental Mercury Adsorption from Simulated Coal Combustion Flue Gas

Tsai

Chiu

Chuang

et al. 2017

Aerosol Air Qual. Res.

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In this study, the Hg 0 adsorption equilibrium and kinetics of a coconut-shell-based activated carbon impregnated with CuCl 2 were examined with respect to their resulting physical and chemical properties. Integrating the results from N 2 adsorption isotherm at 77 K, scanning electron microscopy, elemental analysis, X-ray photoelectron spectroscopy, and Hg 0 adsorption experiments under N 2 and simulated coal-combustion flue gases conditions, it was found that HCl pretreatment could enhance Hg 0 adsorption of crude activated carbon; the Hg 0 adsorption capacities of crude and HCl-pretreated activated carbon under N 2 condition were 95.8 and 225.4 µg g -1 , respectively. Additionally, CuCl 2 impregnation further increased the adsorption capacity of crude. The Hg 0 adsorption capacity of crude activated carbon with 8% CuCl 2 impregnation was 631.1 µg g -1 . However, the equilibrium Hg 0 adsorption capacity decreased when Cu loading exceeded 8 wt%, suggesting that adequate forms of surface Cu, O and Cl interacting with flue gas components and Hg 0 , as well as the presence of pores with specific size ranges allowing rapid transport of the Hg molecules into the interior of the activated carbon and as energy sinker govern the overall chemisorption process. Pseudo-second-order kinetic model could best describe the adsorption behaviors of tested samples under both test conditions, indicating that Hg 0 adsorbed on the activated carbon surface could be explained by bimolecular reaction mechanisms.

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“…Current emission inventories prescribe a fixed Hg 0 : Hg 2+ : Hg p emission ratio for any coal-fired power plant (CFPP), currently 50 % : 40 % : 10 % (Pacyna et al, 2010). Stack data, however, indicate a large variability of the mercury species ratios between CFPPs, depending on multiple parameters such as air pollution control devices (APCD) used and the mercury content of coal burned at a given time (Hsi et al, 2010). Such variations are not accounted for in inventories.…”

Section: Emission Uncertaintiesmentioning

confidence: 99%

Evaluation of discrepancy between measured and modeled oxidized mercury species

Kos¹,

Ryzhkov²,

Dastoor³

et al. 2012

Preprint

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Zhang et al. (2012a), in a recent report, compared model estimates and new observations of oxidised and particulate mercury species (Hg2+ and Hgp) in the Great Lakes region and found that the sum of Hg2+ and Hgp varied between a factor of 2 to 10 between measurements and model. They suggested too high emission inputs and too fast oxidative conversion of Hg0 to Hg2+ and Hgp, as possible causes. This study quantitatively explores in detail the uncertainties in measurements, in addition to the above concerns and speciation of mercury near emission sources in the model to better understand these discrepancies in the context of oxidized mercury, i.e. gaseous (Hg2+) and particulate (Hgp) mercury. These include sampling efficiency, composition of sample, interfering species and calibration errors for measurements and in-plume reduction processes. Sensitivity simulations using Global/Regional Atmospheric Heavy Metals Model (GRAHM) were performed to analyze the role of in-plume reduction on ambient concentrations and deposition of mercury in North America. The discrepancy between simulated and observed concentrations of Hg2+ and Hgp was found to be reduced when a ratio for Hg0:Hg2+:Hgp in the emissions was changed from 50:40:10 (as specified in the original inventories) to 90:8:2 to account for in-plume reduction of Hg0 processes. A significant reduction of the root mean square error (e.g., 19.22 to 11.3 pg m−3 for New Jersey site NJ54) and bias (67.8 to 19.3 pg m−3 for NJ54) for sampling sites in the Eastern United States and Canada, especially for sites near emission sources was found. Significant improvements in the spatial distribution of wet deposition of mercury in North America was noticed. Particularly, over-prediction of wet deposition near anthropogenic sources of mercury was reduced by 43%. On a regional scale, estimated wet deposition improved by a factor of 2 for areas with more than 12 μg m−2 yearly average wet deposition. Model sensitivity simulations show that the measured concentration of oxidized mercury is too low to be consistent with measured wet deposition fluxes in North America. This improvement by a factor of 2 and measurement uncertainties within a factor of 3 to 8 provides a reasonable rationale for the discrepancy of a factor of 2–10 determined by Zhang et al. (2012a)

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Mercury Speciation and Distribution in a 660-Megawatt Utility Boiler in Taiwan Firing Bituminous Coals

Cited by 28 publications

References 1 publication

Evaluation of discrepancy between measured and modelled oxidized mercury species

Evaluation of discrepancy between measured and modelled oxidized mercury species

Influences of Copper(II) Chloride Impregnation on Activated Carbon for Low-Concentration Elemental Mercury Adsorption from Simulated Coal Combustion Flue Gas

Evaluation of discrepancy between measured and modeled oxidized mercury species

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