Mechanisms and roles of fly ash compositions on the adsorption and oxidation of mercury in flue gas from coal combustion

Wang, Yafei; Meng, Yonggang; Zhang, Lei; Hao, Jiming

doi:10.1016/j.fuel.2015.09.065

Cited by 66 publications

(33 citation statements)

References 46 publications

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“…The same commercially pure mercury compounds will be desorbed at different temperatures in the TPDD process because of different solid diluents, such as activated carbon, silica flour and fly ash . Therefore, this study selected the pretreated fly ash which was first heated at 650 °C for 4 h as the solid diluent, and the relevant characteristic temperature parameters are shown in Table . It can been seen that the decomposition temperatures of mercury compounds are in the following order: HgBr 2 < HgCl 2 < HgS(black) < HgO < HgS(red) < HgSO 4 .…”

Section: Resultsmentioning

confidence: 99%

“…Among these flue gas components, Cl is considered to be the most important . Apart from this, partial metal oxides and unburnt carbon in fly ash has positive effects on Hg 0 heterogeneous oxidation . However, because of the low chorine content in coal, only a small part of Hg 0 is transformed into Hg 2+ and Hg p , so that Hg 0 is the main mercury form in the flue gas.…”

Section: Resultsmentioning

confidence: 99%

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Effects of NH₄Br additive on mercury transformation and removal during CFB coal combustion

Zhao

Duan

Zhou

et al. 2016

J of Chemical Tech & Biotech

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BACKGROUND: Mercury emission from coal-fired power plants has caused widespread concern. Halogen is considered to be a good mercury oxidant and many researchers have added it into the coal for mercury removal. However, the mechanism of mercury transformation is still not clear. Effects of NH 4 Br additive on mercury transformation and removal were studied on a 6 kW th circulating fluidized bed (CFB) coal combustor. The main goal of this work is to explore in detail the mercury transformation mechanism in the presence of bromine.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Effects of NH₄Br additive on mercury transformation and removal during CFB coal combustion

Zhao

Duan

Zhou

et al. 2016

J of Chemical Tech & Biotech

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“…Therefore, NO 2 is easily adsorbed by a basic functional group, thereby releasing a large amount of NO adsorption sites. This process promotes the continuous adsorption of NO on the sludge surface, and the denitration rate is significantly improved [33]. …”

Section: Characterizationmentioning

confidence: 99%

Application of Plasma Treatment in Preparation of Soybean Oil Factory Sludge Catalyst and Its Application in Selective Catalytic Oxidation (SCO) Denitration

Zhang

Yang

et al. 2018

Materials

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At present, the most commonly used denitration process is the selective catalytic reduction (SCR) method. However, in the SCR method, the service life of the catalyst is short, and the industrial operation cost is high. The selective catalytic oxidation absorption (SCO) method can be used in a low temperature environment, which greatly reduces energy consumption and cost. The C/N ratio of the sludge produced in the wastewater treatment process of the soybean oil plant used in this paper is 9.64, while the C/N ratio of the sludge produced by an urban sewage treatment plant is 10–20. This study shows that the smaller the C/N ratio, the better the denitration efficiency of the catalyst. Therefore, dried oil sludge is used as a catalyst carrier. The influence of different activation times, and LiOH concentrations, on catalyst activity were investigated in this paper. The denitration performance of catalysts prepared by different activation sequences was compared. The catalyst was characterized by Fourier Transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and scanning electron microscope (SEM). The experimental results showed that: (1) When the concentration of the LiOH solution used for activation is 15%, and the activation time is four hours, the denitration effect of the catalyst is the best; (2) the catalyst prepared by activation before plasma roasting has the best catalytic activity.

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“…The properties of fly ash have the most significant impact on Hg 2+ adsorption. The dust cake layer can also facilitate the oxidation of Hg 0 (Wang et al, 2016a). Some plants apply ESP-FF hybrid precipitator to improve the fine particle removal efficiency.…”

Section: Mercury Transformation In Fabric Filter (Ff)mentioning

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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Mechanisms and roles of fly ash compositions on the adsorption and oxidation of mercury in flue gas from coal combustion

Cited by 66 publications

References 46 publications

Effects of NH₄Br additive on mercury transformation and removal during CFB coal combustion

Effects of NH₄Br additive on mercury transformation and removal during CFB coal combustion

Application of Plasma Treatment in Preparation of Soybean Oil Factory Sludge Catalyst and Its Application in Selective Catalytic Oxidation (SCO) Denitration

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

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Mechanisms and roles of fly ash compositions on the adsorption and oxidation of mercury in flue gas from coal combustion

Cited by 66 publications

References 46 publications

Effects of NH4Br additive on mercury transformation and removal during CFB coal combustion

Effects of NH4Br additive on mercury transformation and removal during CFB coal combustion

Application of Plasma Treatment in Preparation of Soybean Oil Factory Sludge Catalyst and Its Application in Selective Catalytic Oxidation (SCO) Denitration

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

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Effects of NH₄Br additive on mercury transformation and removal during CFB coal combustion

Effects of NH₄Br additive on mercury transformation and removal during CFB coal combustion