Effect of Selective Catalytic Reduction System on Fine Particle Emission Characteristics

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• 作者：Jingjing Bao ; Lin Mao ; Yuhua Zhang ; Hongmei Fang ; Yajuan Shi ; Linjun Yang ; Hongmin Yang
• 刊名：Energy & Fuels
• 出版年：2016
• 出版时间：February 18, 2016
• 年：2016
• 卷：30
• 期：2
• 页码：1325-1334
• 全文大小：575K
• ISSN：1520-5029

文摘

Based on commercial catalysts (V₂O₅–WO₃/TiO₂), the effects of a selective catalytic reduction (SCR) system on the emission characteristics of fine particles were investigated. The size distribution, morphology, element compositions, and chemical compositions of fine particles at the outlet of the SCR system were measured by an electrical low pressure impactor (ELPI), particulate matter (PM₁₀/PM_2.5) samplers, field emission scanning electron microscopy/energy dispersive spectrometry (FSEM–EDS), X-ray diffraction (XRD), etc. The influences of reaction conditions and flue gas components on fine particle formation were also studied. The results reveal that a large number of fine particles can be generated during the SCR process. These fine particles are mostly in the submicrometer size range and appear to be nonuniform. The main components of these fine particles are ammonium sulfate or ammonium bisulfate. There is a good correlation between the formation of fine particles and the SO₂ oxidation rate. Fine particle number concentration at the outlet of the SCR system increases obviously with the reaction temperature and molar ratio of NH₃ to NO (NSR, normalized stoichiometric ratio). Moreover, the enhancement of SO₂, H₂O, and O₂ concentrations in the inlet flue gas would increase the number concentration of the formed fine particles. The effects of the SCR process on the PM_2.5 emission characteristics consist of two aspects. On the one hand, some SO₂ can be oxidized to SO₃ during the SCR process at the function of the catalyst. Then SO₃ would react with NH₃ and H₂O to form ammonium sulfate and ammonium bisulfate particles, which is a reversible process simultaneous with the deNOx reactions. On the other hand, SO₃ can also react with the escaped NH₃ and H₂O to form ammonium sulfate and ammonium bisulfate particles after the SCR system.