Were mercury emission factors for Chinese non-ferrous metal smelters overestimated? Evidence from onsite measurements in six smelters

Zhang, Lei; Wu, Qingru; Meng, Yonggang; Yang, Hai; Wang, Yafei; Hao, Jiming

doi:10.1016/j.envpol.2012.07.036

Cited by 58 publications

(86 citation statements)

References 14 publications

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“…ESP plays the most important role in mercury removal for roasting and/or smelting flue gas. Zhang et al (2012b) found an average mercury removal rate of 12 %, which is much lower than the efficiency of ESPs in coal-fired power plants, because of two reasons. Firstly, higher temperature of ESPs in smelters (300-350 • C compared to more or less 150 • C in coal-fired power plants) would restrain the Hg 0 condensation and Hg 2+ absorption processes (Meij and Winkel, 2006).…”

Section: Mercury Transformation In the Dust Collectorsmentioning

confidence: 99%

“…Hg p proportion after dust collectors is less than 5 % (Zhang et al, 2012b;Wu et al, 2015). Hg 0 can be homogeneously or heterogeneously oxidized in the flue gas, while the charging anode in the ESP can reduce Hg 2+ to Hg 0 .…”

Section: Mercury Transformation In the Dust Collectorsmentioning

confidence: 99%

“…Therefore, the resulting mercury speciation profile after the dust collectors depends on the competition between Hg 2+ reduction and Hg 0 oxidation. The proportion of Hg 2+ after dust collectors varies a lot (4-85 %) among different tested smelters (Zhang et al, 2012b;Wu et al, 2015). The total mercury removal efficiency of dust collectors is usually less than 20 %.…”

Section: Mercury Transformation In the Dust Collectorsmentioning

confidence: 99%

“…To minimize heavy metal emissions, the roasting and/or smelting flue gas could also require additional mercury removal after the purification system (UNECE, 2013). Since the roasting and/or smelting stage releases the most mercury, previous studies focus on mercury transformation and removal inside APCDs for the roasting/smelting flue gas (Zhang et al, 2012b;Wu et al, 2015). Figure 3 shows the mercury speciation after APCDs for non-ferrous metal smelters.…”

Section: Mercury Transformation Across Apcds For the Roasting And/or mentioning

confidence: 99%

“…Usually, mercury is released from concentrates to flue gases during the pyrometallurgical processes of non-ferrous metals. A typical pyrometallurgical process requires four stages, including dehydration, smelting and/or roasting, extraction, and refining (Wang et al, 2010b;Zhang et al, 2012b;Wu et al, 2015). Approximately 1 % of mercury in concentrates is released to flue gas in the dehydration kiln, where the temperature varies from 150 to 700 • C (Song, 2010).…”

Section: Mercury Speciation In the Roasting And/or Smelting Furnacesmentioning

confidence: 99%

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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: Mercury Transformation In the Dust Collectorsmentioning

confidence: 99%

Section: Mercury Transformation In the Dust Collectorsmentioning

confidence: 99%

Section: Mercury Transformation In the Dust Collectorsmentioning

confidence: 99%

Section: Mercury Transformation Across Apcds For the Roasting And/or mentioning

confidence: 99%

Section: Mercury Speciation In the Roasting And/or Smelting Furnacesmentioning

confidence: 99%

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