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Simultaneous removal of elemental mercury and NO from simulated flue gas at low temperatures over Mn-V-W/TiO2 catalysts Jialin Meng, Yufeng Duan, Peng Hu, Yifan Xu, Xinze Geng, Ting Yao, Shaojun Ren, and Hongqi Wei Energy Fuels, Just Accepted Manuscript • DOI: 10.1021/acs.energyfuels.9b01503 • Publication Date (Web): 18 Aug 2019 Downloaded from pubs.acs.org on August 23, 2019
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Energy & Fuels
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Simultaneous removal of elemental mercury and NO from simulated flue gas at low temperatures over Mn-V-W/TiO2 catalysts
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Jialin Meng, Yufeng Duan*, Peng Hu, Yifan Xu, Xinze Geng, Ting Yao, Shaojun Ren, Hongqi
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Wei
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Key Laboratory of Energy Thermal Conversion and Control of Ministry of Education, School
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of Energy and Environment, Southeast University, Nanjing, 210096, China.
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KEYWORDS: Simultaneous removal; Elemental mercury; NO; Catalytic activity; Mn-V-
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W/TiO2
1 2
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ABSTRACT A series of Mn-V-W/TiO2 (Mn-VWT) catalysts were synthesized by
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impregnation method, and calcinated at different temperature (300-600oC). To explore the
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effect of reaction temperature, SO2, and H2O on the simultaneous removal performance of
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elemental mercury (Hg0) and NO, Mn-VWT were investigated by fixed-bed reaction system.
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Various techniques (SEM, BET, XRD, H2-TPR, NH3-TPD and XPS) were utilized to
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characterize the samples. The results showed that the catalytic activity of Mn-VWT increased
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first and then decreased with the increasing calcination temperature. The removal efficiency of
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Hg0 and NO still had good performance even in low reaction temperature (200oC), reached to
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100% and 82%, respectively. Mn-VWT-400 had the best simultaneous removal performance,
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due to the highest content of the Mn4+, V4+ and chemisorbed oxygen Oα, and the best reductive
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activity at low temperature. Furthermore, SO2 irreversibly inhibited Hg0 and NO removal
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ability due to the sulfate and sulfite generation on the surface of Mn-VWT-400. Especially, the
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inhibition effect was more serious in the case of SO2 and H2O coexisted, because of the rate of
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sulfate/sulfite was higher than that of former. In addition, with the reaction temperature
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increased, the effect of SO2 and H2O on the removal of Hg0 and NO over Mn-VWT was
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gradually reduced.
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1. INTRODUCTION
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Mercury and its compounds are considered as the hazardous substances due to the
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hazardous impact on human health and environment.1-3 On August 16, 2017, the Minamata
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Convention, the first legally binding international treaty to prevent mercury emissions, came
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into force, aiming at reducing anthropogenic mercury emission.4 Mercury emission from coal
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combustion is one of the most significant emission source, accounting for about 30% of the
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total mercury emission. Mercury in coal-fired flue gas mainly exists in three forms5: oxidized
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mercury (Hg2+), elemental mercury (Hg0) and particulate mercury (Hgp). Hgp can be trapped
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by particle control device, such as electrostatic precipitator (ESP) or fabric filter (FF). Hg2+ is
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water soluble and can be removed by wet flue gas desulfurization (WFGD) unit. The Hg0
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emission control is difficult due to its inertia physical and chemical property and insoluble in
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water.6 NOx emission can be effectively reduced by the selective catalytic reduction (SCR)
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technology, which is widely used at present.7 Previous studies showed that,8-10 mercury in coal-
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fired flue gas can be co-beneficially captured by the catalytic oxidation removed downstream
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of and further removed downstream of the conventional air pollution control devices (APCDs)
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of ESP/FF, WFGD or wet ESP. Compared with the activated carbon injection (ACI), the co-
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beneficial removal of mercury by the APCDs is much more cost-effective and environmentally
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friendly.11 Therefore, developing the dual-effective SCR catalyst for both NO and Hg co-
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Energy & Fuels
removal is one of the most promising technology applied in coal fired power plant.
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The most commercialized SCR catalyst of V2O5-WO3-TiO2 (V-W/TiO2) has been found
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its widely utilization.12 However, the active temperature window of the V-W/TiO2 catalyst is
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narrowed to 300-400oC, which is limited in lots of process where the flue gas temperature is
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lower beyond it, for example, in case of the boiler load declined or the condition of the sintering
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machine in iron and steel works. Furthermore, the expensive catalysts exposed to high
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concentrations of fly ash and acid gases could reduce its service life.13 Meanwhile, this
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temperature window is far from the optimal oxidation temperature of Hg0, thus limiting its
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utility application for NO and Hg co-removal both in coal-fired power plants and in the non-
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power production industries.14 Accordingly, it is essential to develop new type SCR catalyst
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with good simultaneous removal effect of both NO and mercury at low temperature (
