一种典型钒钛系SCR催化剂SO3生成特性研究

doi:10.11949/0438-1157.20201429

摘要/Abstract

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

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 SO₃formation; O₂concentration has no significant effect on the formation of SO₃on 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

中图分类号:

X 511

尹子骏, 苏胜, 卿梦霞, 赵志刚, 王中辉, 王乐乐, 江龙, 汪一, 胡松, 向军. 一种典型钒钛系SCR催化剂SO₃生成特性研究[J]. 化工学报, 2021, 72(5): 2596-2603.

YIN Zijun, SU Sheng, QING Mengxia, ZHAO Zhigang, WANG Zhonghui, WANG Lele, JIANG Long, WANG Yi, HU Song, XIANG Jun. Study on SO₃ formation characteristics of a typical vanadium titanium SCR catalyst[J]. CIESC Journal, 2021, 72(5): 2596-2603.

图/表 15

表1 催化剂化学成分的检测结果（质量分数）

Table 1 Test results of XRF of catalyst

Ti	W	V	S	Si	Al	Fe	Ca	其他
83.88%	6.48%	1.51%	1.42%	2.56%	1.06%	0.09%	0.93%	2.07%

表2 催化剂比表面积检测结果

Table 2 Test results of BET of catalyst

比表面积/(m²/g)	孔容/(cm³/g)	平均孔径/nm
65.38	0.32	19.17

图1 实验系统装置图

Fig.1 Schematic diagram of experimental setup

表3 SO3生成实验的实验工况参数

Table 3 Experimental condition parameters of SO3 generation experiment

温度/℃	流量/(L/min)	气体成分
360	0.5~1.5	600×10^-6 SO₂、3% O₂、N₂平衡
280~400	1	600×10^-6 SO₂、3% O₂、N₂平衡
360	1	(400~1200)×10^-6 SO₂、3% O₂、N₂平衡
360	1	600×10^-6 SO₂、1.5%~10% O₂、N₂平衡

表4 不同SO2浓度下反应系统SOx收集率

Table 4 SOx collection rate of reaction system under different SO2 concentration

SO₂体积

分数

系统入口SO₂总量/mmol

冷凝管中SO₃生成量/mmol

吸收液中SO₂含量/mmol

SO_x收集

率/%

图2 SO2转化率随流量的变化规律

Fig.2 Variation of SO2 conversion with flowrate

图3 SO2转化率随温度的变化规律

Fig.3 Variation of SO2 conversion with temperature

图4 SO2转化率随SO2浓度的变化规律

Fig.4 Variation of SO2 conversion with SO2 concentration

图5 SO2转化率随O2浓度的变化规律

Fig.5 Variation of SO2 conversion with O2 concentration

图6 SO2浓度对SO2氧化速率的影响

Fig.6 Dependence of SO2 conversion rate on SO2 concentration

图7 不同温度下lnrSO2与lnCSO2的关系

Fig.7 lnrSO2–lnCSO2 at various temperatures

图8 O2浓度对SO2氧化速率的影响

Fig.8 Dependence of SO2 conversion rate on O2 concentration

图9 不同温度下lnrSO2与lnCO2的关系

Fig.9 lnrSO2–lnCO2 at various temperatures

表5 表观速率常数与反应温度的关系

Table 5 Relationship between rate constant and reaction temperature

反应温度/℃	表观速率常数×10⁷/ (L/(g?min))
280	4.80
320	8.42
360	27.74
400	68.47

图10 SO2氧化的lnkabs与1/T关系曲线

Fig.10 Curve of lnkabs–1/T for SO2 oxidation

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一种典型钒钛系SCR催化剂SO₃生成特性研究

Study on SO₃ formation characteristics of a typical vanadium titanium SCR catalyst

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