Speciation of As, Cr, Se and Hg under coal fired power station conditions

Shah, Pushan; Strezov, Vladimir; Prince, Kathryn; Nelson, Peter F.

doi:10.1016/j.fuel.2007.12.001

Cited by 155 publications

(104 citation statements)

References 36 publications

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“…Whether it occurs in pyrite or is organically associated, such weak bonding allows Se to be easily released and almost completely volatilised during combustion. Irrespective of its mode of occurrence in the coal matrix, Se might react with Ca and form stable compounds such as CaSeO 3 (Shah et al, 2008) condensing on the surface of ash particles. Moreover, the selenate oxyanion resembles sulphate in structure and charge, and forms a partial solid solution (CaSeO 4 -CaSO 4 )·2H 2 O (Freyer and Voigt, 2003).…”

Section: Seleniummentioning

confidence: 99%

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Leaching behaviour of elements from coal combustion fly ash: An overview

Izquierdo

Querol

2012

International Journal of Coal Geology

633

379

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Coal-based power generation produces over 750 Mt of coal ash per year globally, but under 50% of world production is utilised. Large amounts of fly ash are either stored temporarily in stockpiles, disposed of in ash landfills or lagooned. Coal ash is viewed as a major potential source of release of many environmentally sensitive elements to the environment. This paper encompasses over 90 publications on coal fly ash and demonstrates that a large number of elements are tightly bound to fly ash and may not be easily released to the environment, regardless of the nature of the ash. This review provides an extensive look at the extent to which major and trace elements are leached from coal fly ash. It also gives an insight into the factors underlying the leachability of elements and addresses the causes of the mobility. The mode of occurrence of a given element in the parent coal was found to play an important role in the leaching behaviour of fly ash. The amount of calcium in fly ash exerts a dominant influence on the pH of the ash-water system. The mobility of most elements contained in ash is markedly pH sensitive. The alkalinity of fly ash attenuates the release of a large number of elements of concern such as Cd, Co, Cu, Hg, Ni, Pb, Sn or Zn among others, but at the same time, it enhances the release of oxyanionic species such as As, B, Cr, Mo, Sb, Se, V and W. The precipitation of secondary phases such as ettringite may capture and bind several pollutants such ash As, B, Cr, Sb, Se and V.

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Section: Seleniummentioning

confidence: 99%

“…Se 4+ appears to be the dominant species in fly ash and its leachates (Cornelis et al, 2008;Iwashita et al, 2005;Shah et al, 2008;van der Hoek et al, 1994). Selenite and selenate compounds are relatively mobile, and display a higher solubility compared to other metalates (Cornelis et al, 2008).…”

Section: Seleniummentioning

confidence: 99%

Leaching behaviour of elements from coal combustion fly ash: An overview

Izquierdo

Querol

2012

International Journal of Coal Geology

633

379

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“…FF is increasingly applied in coal-fired power plants and industrial boilers in the need of fine particle (PM 2.5 or PM 1 ) control. FF has mercury removal efficiencies of 9-92 % with an average of 67 % (Chen et al, 2007;Shah et al, 2008;Wang et al, 2009;ICR, 2010). Besides Hg p , FF can also remove over 50 % of Hg 2+ .…”

Section: Mercury Transformation In Fabric Filter (Ff)mentioning

confidence: 99%

“…Mercury speciation profiles in the flue gas from coal combustion are summarized in Table 1, which considers the transformation of mercury species across different types of APCDs (Goodarzi, 2004;Guo et al, 2004;Kellie et al, 2004;Tang, 2004;Duan et al, 2005;Lee et al, 2006;Zhou et al, 2006;Chen et al, 2007;Yang et al, 2007;Chen et al, 2008;Shah et al, 2008Shah et al, , 2010Wang et al, 2008;Zhou et al, 2008;Kim et al, 2010b;Wang et al, 2010a;Zhang, 2012;Zhang et al, 2012a;L. Zhang et al, 2013b).…”

Section: Mercury Speciation Profile For Coal-fired Boilersmentioning

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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“…The observed neutralization of the high pH in the control sample to the AMC sample suggests that more calcium will be available as Ca 2+ to react with either CO 2 or SO 2 . Extensive studies on mercury [13,[54][55][56][57][58][59][60] have suggested that the majority of Hg in post desulfurization flue gas is typically in elemental form, which can be oxidized by soluble inorganic oxides (i.e., CaO) or chlorine [60], and potentially adsorb to unburned carbon in the fly ash. However, since fly ash from JBPP has low or insignificant unburned carbon content, this mechanism might not explain the increase in mercury content of the fly ash.…”

Section: Carbonatesmentioning

confidence: 99%

Field Application of Accelerated Mineral Carbonation

2014

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Globally, coal-fired power plants are the largest industrial source of carbon dioxide (CO 2 ). CO 2 emissions from flue gas have potential for direct mineralization with electrostatic precipitator fly ash particles in the field. Demonstration scale accelerated mineral carbonation (AMC) studies were conducted at the Jim Bridger Power Plant, a large coal fired power plant located in Wyoming, USA. AMC produces kinetically rapid conditions for increased rates of mineralization of CO 2 , sulfur dioxide (SO 2 ) and mercury (Hg) on fly ash particles. Control and AMC reacted fly ash particles were investigated for: change in carbon (expressed as CaCO 3 ), sulfur (expressed as SO 4 2− ), and mercury (Hg) contents; topology and surface chemical composition by scanning electron microscope/energy dispersive X-ray spectroscopy analysis; chemical distribution of trace elements; and aqueous mineral solubility by the toxicity characteristic leaching procedure. Results of the AMC process show an increase in C, S, and Hg on AMC fly ash particles suggesting that multiple pollutants from flue gas can be removed through this direct mineral carbonation process. Results also suggest that the AMC process shifts soluble trace elements in fly ash to less leachable mineral fractions. The results of this study can provide insight into potential successful field implementation of AMC.

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Speciation of As, Cr, Se and Hg under coal fired power station conditions

Cited by 155 publications

References 36 publications

Leaching behaviour of elements from coal combustion fly ash: An overview

Leaching behaviour of elements from coal combustion fly ash: An overview

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

Field Application of Accelerated Mineral Carbonation

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