Interpreting enhanced Hg oxidation with Br addition at Plant Miller

Niksa, Stephen; Naik, Chitralkumar V.; Berry, Mark; Monroe, Larry

doi:10.1016/j.fuproc.2009.05.022

Cited by 27 publications

(24 citation statements)

References 1 publication

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“…Niksa et al (2002) first suggested a three-step heterogeneous reaction mechanism for catalytic chlorination of mercury on the surface of unburned carbon particles which include a number of assumptions whereby the sticking coefficients for all the reactions were set to one. The heterogeneous mechanism has been extended to eight steps (Niksa et al, 2009) with analogy made to heterogeneous mercury bromination. A somewhat different approach for the study of the retention of mercury on ash particles is adsorption/desorption theory which has been conducted by Sable et al (2008) by using a Langmuir Hinshelwood model.…”

Section: Emission Of Mercurymentioning

confidence: 99%

Combustion modelling opportunities and challenges for oxy-coal carbon capture technology

Edge

Gharebaghi

Irons³

et al. 2011

Chemical Engineering Research and Design

163

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Section: Emission Of Mercurymentioning

confidence: 99%

Combustion modelling opportunities and challenges for oxy-coal carbon capture technology

Edge

Gharebaghi

Irons³

et al. 2011

Chemical Engineering Research and Design

163

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“…Another means of capture mercury involves the oxidation of Hg 0 by chlorine and bromine species present in the flue gases [19][20], as well as the use of FGD oxidation additives, such us potassium permanganate and Fenton reagents. The oxidation rates of potassium permanganate are very high [21].…”

Section: Introductionmentioning

confidence: 99%

Control of Hg0 re-emission from gypsum slurries by means of additives in typical wet scrubber conditions

Ochoa-González

Dı́az-Somoano

Martı́nez-Tarazona

2013

Fuel

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The effect of different additives on the re-emission of Hg 0 in wet limestone-based flue gas desulphurisation (WFGD) conditions is assessed. Because re-emission of elemental mercury from natural limestone is dependent on the pH of the gypsum slurry, re-emission of elemental mercury was evaluated for different additives using gypsum slurry with a constant pH value of 7. The additives investigated included oxidizing and reducing agents (Fenton reagents and sodium thiosulphate) and also chelating agents (2,4,6 trimercaptotriazine trisodium and sodium hydrosulfide). Fenton reagents were added to prevent the reduction of oxidized mercury species as H 2 O 2 was the precursor used to convert sulfite ions into sulphate or to oxidize Hg 0 . Thiosulphate were added so that mercury could be retained in the gypsum at low concentrations as insoluble HgS, while mercury is being stabilized in the liquid fraction at higher additive doses. The addition of 2,4,6 trimercaptotriazine trisodium (TMT) and NaHS in low doses prevented the reduction of oxidized mercury species as insoluble HgS and Hg 3 (TMT) precipitate onto the gypsum slurry. TMT was found to be most effective additive for Hg 2+ capture.

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“…HBr concentration plateaus at 973 K, Br 2 peaks at 573-773 K. When the temperature is lower than 573 K, the concentration of BrCl increases. Niksa [13] revealed that Hg oxidation begins as the flue gas temperature drops below 873 K, so the influence of O 3 on Hg 0 oxidation depends on the temperature zone into which the O 3 is injected. At about 1650 K, chlorine converts to Cl atom and HCl.…”

Section: Discussionmentioning

confidence: 99%

“…Considering that the rate constant of reaction (7) is close to that of reaction (10), the influence of O 3 on Hg 0 oxidation by BrCl is analogous to that of Hg 0 oxidation by the Br atom. Figure 12 compares the rate constants of reactions (2), (5), (8), (12) and (13). Reaction (13) is hindered by a very high energy barrier and the rate constant is comparatively low.…”

Section: Energy Variations In the Reaction Processesmentioning

confidence: 99%

“…Br species can oxidize Hg 0 effectively [10][11][12]. Niksa [13] described a detailed reaction mechanism for Hg oxidation by Br species in flue gas, which showed that Br species were much more effective than Cl species. O 3 can also oxidize Hg 0 [14], and ionization of O 2 in electrostatic precipitators (ESP) inevitably leads to generation of O 3 .…”

Section: Introductionmentioning

confidence: 99%

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Quantum chemistry investigation on the reaction mechanism of the elemental mercury, chlorine, bromine and ozone system

Gao

Yang

et al. 2015

J Mol Model

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Ab initio calculations were performed to study the quantum chemistry reactions mechanisms among Hg(0), elemental halogen and O3. The geometry of reactions, transition states (TS), intermediates (M) and products were optimized using the MP2 method at the SDD basis function level for Hg, and using 6-311++G (3df, 3pd) for other species. Molecular energies were calculated at QCISD (T) level with zero point energy. Activation energies were calculated along with pre-exponential factors . The reaction rate constants within 298-1800 K were calculated according to transition state theory (TST). The influences of O3 on the reaction of Hg(0) with halogen are discussed. Hg(0) can be oxidized to Hg(1+) by halogen and O3, and halogen and O3 can be arranged in decreasing order as: Br2 > BrO > O3 > Br > Cl, BrCl > HBr > HCl, Br2 > Cl2 according to reaction rate constants. When O3 is presented, Br2, HBr, BrCl, Cl2 and HCl react with O3 and are initially converted to BrO and ClO. O3 is unfavorable for oxidation of Hg(0) by Br2. The mixture of HBr and O3 has better oxidizing Hg(0) performance than HBr and O3. Cl is less effective than Br for oxidation of Hg(0).

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Interpreting enhanced Hg oxidation with Br addition at Plant Miller

Cited by 27 publications

References 1 publication

Combustion modelling opportunities and challenges for oxy-coal carbon capture technology

Combustion modelling opportunities and challenges for oxy-coal carbon capture technology

Control of Hg0 re-emission from gypsum slurries by means of additives in typical wet scrubber conditions

Quantum chemistry investigation on the reaction mechanism of the elemental mercury, chlorine, bromine and ozone system

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