Abstract:

Selective catalytic reduction (SCR) technology is widely used in flue gas nitrogen oxide emission control due to its high denitration efficiency and good selectivity; however, currently widely used vanadium titanium SCR catalyst can oxidize SO₂ in flue gas into SO₃, and excessive SO₃ in flue gas will cause serious impact on the safe operation of power plant and also cause environmental pollution. Taking commercial V₂O₅-WO₃/TiO₂ catalyst as the research object, the effects of flue gas flowrate, temperature, O₂ concentration and SO₂ concentration on the formation of SO₃ on the catalyst during SCR denitrification were systematically studied, and the reaction kinetics of SO₃ formation was further discussed. The results show that the reaction order of SO₂ is 0.59. When the concentration of O₂ is more than 3%, the reaction order of O₂ is 0, and the activation energy of SO₃ formation on catalyst is 70.39 kJ/mol. The increase of SO₂ concentration will increase the reaction rate of SO₃ formation; O₂ concentration has no significant effect on the formation of SO₃ on the catalyst. The temperature of flue gas has a significant effect on the formation of SO₃, and high temperature can promote the formation of SO₃.

Key words: SCR catalyst, coal fired flue gas, SO₂, SO₃, reaction kinetics

摘要：

选择性催化还原（SCR）技术由于脱硝效率高、选择性好而被广泛应用于烟气氮氧化物排放控制；然而，目前广泛采用的钒钛系SCR脱硝催化剂会使烟气中SO₂氧化成SO₃，烟气中过高的SO₃对电厂安全运行会造成严重影响，也会对环境造成污染。以典型V₂O₅-WO₃/TiO₂催化剂为研究对象，系统研究了SCR脱硝过程中烟气流量、温度、O₂浓度、SO₂浓度等对催化剂表面SO₃生成特性的影响，并进一步对SO₃生成的反应动力学特性进行了分析。研究表明：催化剂表面SO₃生成反应中SO₂的反应级数为0.59，当O₂浓度大于3%时，O₂的反应级数为0，该反应的表观活化能为70.39 kJ/mol；实验条件下，烟气中SO₂浓度增加会使SO₃生成的反应速率提高；O₂浓度对催化剂表面SO₃生成影响并不显著；烟气温度对催化剂表面SO₃生成具有显著影响，高温会促进SO₃的生成。

关键词: SCR催化剂, 燃煤烟气, SO₂, SO₃, 反应动力学