Abstract:

Selective catalytic reduction (SCR) can effectively remove pollutant NO _x from flue gas, but it also catalyzes the generation of SO₃, endangering equipment safety and atmospheric environment. In this study, the effects of temperature, flue gas atmosphere and catalyst components on the catalytic production of SO₃ by SCR catalyst were investigated on a simulated SCR equipment. The changes of the catalyst before and after reaction were analyzed by X-ray fluorescence spectroscopy (XRF) and X-ray photoelectron spectroscopy (XPS). The results showed that the yield of SO₃ increased with temperature and O₂ content could affect the SO₃ production, but the effect was minimal with O₂ content over 2%. Increasing SO₂ concentration decreased SO₃ production rate, but total SO₃ amounts still increased. At a certain concentration of NH₃, the formation of SO₃ was significantly inhibited, and a large amount of sulfur and ammonium salt deposition was produced. However, the oxidizing gas NO₂ in NO _x could increase the proportion of V⁵⁺ in the catalyst and promote the formation of SO₃. In the actual reaction process, denitrification competes with SO₂ oxidation. Reducing the NO₂ concentration in flue gas could improve the denitrification efficiency and reduce the generation of SO₃. The vanadium and titanium in the catalyst could increase the formation rate of SO₃, while the silicon could inhibit the formation of SO₃. This study provides a theoretical basis and reference for the operation optimization of actual SCR.

Key words: selective catalytic reduction (SCR) catalyst, catalytic oxidation, SO₃ generation, flue gas atmosphere, active component

摘要：

选择性催化还原（SCR）设备可以有效脱除烟气污染物NO _x，但也会催化生成SO₃，从而危害设备安全和大气环境。本研究在模拟SCR实验台基础上考察了温度、烟气气氛和催化剂组分对SCR催化剂催化生成SO₃的影响，并采用X射线荧光光谱（XRF）和X射线光电子能谱（XPS）分析了催化剂在反应前后的变化。结果表明：温度升高会提高SO₃的生成率；O₂含量对SO₃的生成产生影响，但是O₂含量超过2%后影响微小；增大SO₂浓度会降低SO₃生成率，但SO₃总量仍不断提升；一定浓度的NH₃显著抑制了SO₃的生成，同时产生大量硫铵盐沉积物，而NO _x 中的氧化性气体NO₂会提高催化剂中V⁵⁺的比例，促进SO₃生成；实际反应过程中脱硝与SO₂氧化存在竞争，降低烟气中NO₂浓度会提升脱硝效率且减少SO₃生成；催化剂中的钒和钛会提高SO₃生成率，而硅对SO₃的生成有抑制作用。本研究为SCR的实际运行优化提供了一定的理论基础和参考。

关键词: 选择性催化还原催化剂, 催化氧化, SO₃生成, 烟气气氛, 活性组分