Speciation of mercury in fly ashes by temperature programmed decomposition

López-Antón, M. Antonia; Perry, Ron; Abad-Valle, Patricia; Dı́az-Somoano, Mercedes; Martı́nez-Tarazona, M. Rosa; Maroto‐Valer, M. Mercedes

doi:10.1016/j.fuproc.2010.12.002

Cited by 91 publications

(51 citation statements)

References 27 publications

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“…Additives, usually gypsum, are then mixed with clinker and milled to produce cement. The temperature of the final cement production is usually under 100 • C. Results from temperature programmed decomposition (TPD) experiments indicate that mercury is not released from gypsum at such temperatures (Rallo et al, 2010;López-Antón et al, 2011;Liu et al, 2013). Therefore, we only consider the clinker production process that includes shaft kilns, wet rotary kilns, dry rotary kilns, and precalciner processes.…”

Section: Cement Clinker Production Processesmentioning

confidence: 99%

Mercury transformation and speciation in flue gases from anthropogenic emission sources: a critical review

et al. 2016

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Abstract. Mercury transformation mechanisms and speciation profiles are reviewed for mercury formed in and released from flue gases of coal-fired boilers, non-ferrous metal smelters, cement plants, iron and steel plants, waste incinerators, biomass burning and so on. Mercury in coal, ores, and other raw materials is released to flue gases in the form of Hg 0 during combustion or smelting in boilers, kilns or furnaces. Decreasing temperature from over 800 • C to below 300 • C in flue gases leaving boilers, kilns or furnaces promotes homogeneous and heterogeneous oxidation of Hg 0 to gaseous divalent mercury (Hg 2+ ), with a portion of Hg 2+ adsorbed onto fly ash to form particulate-bound mercury (Hg p ). Halogen is the primary oxidizer for Hg 0 in flue gases, and active components (e.g., TiO 2 , Fe 2 O 3 , etc.) on fly ash promote heterogeneous oxidation and adsorption processes. In addition to mercury removal, mercury transformation also occurs when passing through air pollution control devices (APCDs), affecting the mercury speciation in flue gases. In coal-fired power plants, selective catalytic reduction (SCR) system promotes mercury oxidation by 34-85 %, electrostatic precipitator (ESP) and fabric filter (FF) remove over 99 % of Hg p , and wet flue gas desulfurization system (WFGD) captures 60-95 % of Hg 2+ . In non-ferrous metal smelters, most Hg 0 is converted to Hg 2+ and removed in acid plants (APs). For cement clinker production, mercury cycling and operational conditions promote heterogeneous mercury oxidation and adsorption. The mercury speciation profiles in flue gases emitted to the atmosphere are determined by transformation mechanisms and mercury removal efficiencies by various APCDs. For all the sectors reviewed in this study, Hg p accounts for less than 5 % in flue gases. In China, mercury emission has a higher Hg 0 fraction (66-82 % of total mercury) in flue gases from coal combustion, in contrast to a greater Hg 2+ fraction (29-90 %) from non-ferrous metal smelting, cement and iron and/or steel production. The higher Hg 2+ fractions shown here than previous estimates may imply stronger local environmental impacts than previously thought, caused by mercury emissions in East Asia. Future research should focus on determining mercury speciation in flue gases from iron and steel plants, waste incineration and biomass burning, and on elucidating the mechanisms of mercury oxidation and adsorption in flue gases.

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Section: Cement Clinker Production Processesmentioning

confidence: 99%

Mercury transformation and speciation in flue gases from anthropogenic emission sources: a critical review

et al. 2016

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“…Lopez-Anton et al [31] stated that the thermal decomposition temperature of HgCl 2 was 70 °C. There were two different forms of crystal structure, black cube HgS and red six party HgS, respectively.…”

Section: Sample Heatingmentioning

confidence: 99%

“…(4a) shows the release curves of Hg compounds in different ash samples at the temperature of 80 °C. According to Lopez-Anton et al [31], the HgCl 2 captured by fly ash begins to release at 70 °C. Thus, the capture of HgCl 2 by ashes would be detected in the decrease in mercury concentrations when the ashes were heated at 80 °C.…”

Section: Chemical Composition and Adsorption Of Mercurymentioning

confidence: 99%

Thermal Stability and Adsorption of Mercury Compounds in Fly Ash

Zhong¹,

Li²,

Jiang³

2016

TOEFJ

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Fly ashes were collected from five power plants under two loads in China. The ashes were heated at four different temperatures, and mercury speciation was determined based on the release regular pattern of mercury with temperature. The mercury concentration, unburned carbon content and mean ash particle sizes were measured. The correlation of mercury capture and unburned carbon content, mean ash particle sizes were analyzed. Results indicate that the amount of unburned carbon and mercury adsorb is significantly positively correlated in fly ash; the smaller the mean ash particle size, the more mercury particles are captured. There was little HgO and HgSO 4 , and the main form of mercury compounds in fly ash were HgCl 2 and HgS. The high element Cl content can result in high HgCl 2 ratio in particular mercury and element S play an important role in adsorbing mercury.

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“…FA can also be employed as a mercury adsorbent for removing gaseous mercury from flue gas (Hassett and Eylands, 1999;Serre and Silcox, 2000;Hutson, 2008 (Galbreath and Zygarlicke, 2000;Lopez-Anton et al, 2011). The present form of Hg 2+ was found to be HgCl 2 and HgO primarily, which could be adsorbed on the residual carbon surface in FA (Galbreath and Zygarlicke, 2000;Lopez-Anton et al, 2011).…”

Section: Introductionmentioning

confidence: 99%

Emission and Species Distribution of Mercury during Thermal Treatment of Coal Fly Ash

Wang

Shi

Chiang

et al. 2016

Aerosol Air Qual. Res.

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The thermal treatment of coal fly ash (FA) utilized by industries will inevitably lead to the emission of mercury, potentially causing atmospheric pollution. The present study is aimed at understanding the emission amount and species distribution of mercury during FA thermal treatment, and attempts were made to further provide basic data of mercury emission for environmental utilization of the FA by industries as raw materials. The physio-chemical properties of FA were analyzed and FA samples were heated at 200-1200°C in a tubular furnace in an oxidizing atmosphere. Thermogravimetric analysis (TGA) was carried out to determine the content of residual carbon in FA. The mercury species distribution was determined using United States EPA method 3200. The results indicated that semi-mobile mercury was the main mercury species in FA. Owing to the adsorption of residual carbon on Hg 0 , more residual carbon which lead to higher proportion of semi-mobile obtained in coarser size grades. 20% of total mercury emitted at 206°C, followed by a rapid growth of the emission rate of mercury at above 206°C, and the emission of total mercury achieved to be 50% and 90% corresponding to 291°C and 515°C, respectively. A distinct transformation from semi-mobile mercury to extractable mercury occurred at 200°C due to catalytic oxidation of Hg 0 and enhance the mobility and potential toxicity of mercury. Both extractable and semi-mobile mercury decreased sharply at 300-400°C. Finally, the non-mobile mercury was emitted with combustion of residual carbon in FA at 600-800°C. It was thus concluded that measures would be taken to control emission of mercury for environmentally friendly utilization of coal FA by industries when the FA was heated higher than 300°C.

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Speciation of mercury in fly ashes by temperature programmed decomposition

Cited by 91 publications

References 27 publications

Mercury transformation and speciation in flue gases from anthropogenic emission sources: a critical review

Mercury transformation and speciation in flue gases from anthropogenic emission sources: a critical review

Thermal Stability and Adsorption of Mercury Compounds in Fly Ash

Emission and Species Distribution of Mercury during Thermal Treatment of Coal Fly Ash

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