Effect of potassium compounds in sintering flue gas on the removal of NO and dioxin performance over V2O5–WO3/TiO2 catalyst
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摘要: 采用釩鎢鈦催化劑可有效減排燒結煙氣中NO和二噁英，而煙氣中含有的鉀鹽會造成催化劑活性降低。在實驗室采用濕式浸漬法對新鮮釩鎢鈦催化劑進行強制失活，研究了三種鉀鹽（K2SO4、K2O和KCl）負載于催化劑表面對其脫硝和脫二噁英活性的影響，并采用水洗和酸洗手段考察了失活催化劑的再生性能。結果表明，不同形態鉀鹽會造成催化劑的脫硝和脫二噁英活性降低，催化劑對兩種污染物的活性降低順序遵循相同的規律，即KCl> K2O> K2SO4。催化劑的失活機理主要包括物理失活和化學失活。物理失活主要是指鉀鹽在催化劑表面沉積并堵塞其孔道；化學失活主要是指鉀鹽與催化劑表面的活性組分產生相互作用，鈍化表面活性位點，降低表面酸性，減弱氧化和還原性能，進而降低催化劑的脫硝和脫二噁英活性。再生實驗結果表明，水洗可以一定程度上恢復催化劑的脫硝活性，酸洗會導致催化劑表面活性物質流失，但水洗和酸洗均無法有效恢復催化劑的脫二噁英活性。最后，提出了不同形態鉀鹽對釩鎢鈦催化劑的中毒機理。
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關鍵詞:
- 燒結煙氣 /
- 脫硝 /
- 脫二噁英 /
- V2O5?WO3/TiO2催化劑 /
- K中毒
Abstract: Sintering is one of the most important processes in iron and steel production, which provides stable sinter for the blast furnace. However, it also produces pollutants, such as sulfur dioxide (SO2), nitrogen oxide (NOx), and dioxins, which cause serious environmental problems. With the increasing pressure of environmental protection, pollutant reduction has become one of the bottlenecks restricting the development of iron and steel enterprises. Using a vanadium–tungsten–titanium catalyst can effectively reduce NO and dioxin in the sintering flue gas, while the potassium salt contained in the flue gas will reduce the activity of the catalyst. In this study, the fresh vanadium–tungsten–titanium catalyst was deactivated by the wet impregnation method in the laboratory. Effects of three potassium salts (K2SO4, K2O, and KCl) loaded on the surface of the catalyst on its denitration and dioxin removal activities were investigated. The regeneration performance of the deactivated catalyst was studied by the water washing and acid pickling process. Results confirmed that activities of denitration and dioxin removal were reduced by different potassium salts, and the order of reduction follows the sequence: KCl>K2O>K2SO4. The deactivation mechanism of the catalyst mainly includes physical deactivation and chemical deactivation. Physical deactivation is mainly caused by the deposition of potassium salts on the surface of the catalyst, blocking its pores. Chemical deactivation mainly refers to the interaction between the potassium salts and the active component on the catalyst’s surface, which inactivates the surface’s active site, weakens its oxidation reducibility, and reduces the number of acid sites on the surface, thereby decreasing the denitration and dioxin removal activities of the catalyst. Regeneration experiment results showed that water washing could restore the denitration activity of the catalyst. Acid pickling would lead to the loss of active substances on the surface of the catalyst. However, neither water washing nor acid pickling could effectively restore the dioxin removal activity of the catalyst. Finally, the poisoning mechanism of different potassium salts on the vanadium–tungsten–titanium catalyst was proposed.-
Key words:
- sintering flue gas /
- denitration /
- dedioxin /
- V2O5?WO3/TiO2 catalyst /
- potassium poisoning
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圖 1 催化劑活性測試反應裝置
Figure 1. Schematic of the laboratory activity test of catalysts
1—Gas; 2—CB bubbler; 3—Pressure gauge; 4—Control panel; 5—Flow-control valve; 6—Inlet valve; 7—Gas mixture; 8—Preheating furnace; 9—Catalyst; 10—Heating furnace; 11—Quartz tube; 12—Gas analyzer; 13—Meteorological chromatograph
圖 2 不同形態鉀鹽中毒對催化劑活性的影響. (a) 脫硝活性; (b) CB降解活性
Figure 2. Catalytic activity of catalysts poisoned by different K+ species: (a) NO conversion; (b) CB conversion
圖 3 不同形態鉀鹽負載后催化劑的XRD圖譜
Figure 3. XRD patterns of catalysts poisoned by different K+ species
圖 4 不同形態鉀鹽負載后催化劑的H2-TPR圖譜
Figure 4. H2-TPR profiles of catalysts poisoned by different K+ species
圖 5 不同形態鉀鹽負載后催化劑的NH3-TPD圖譜
Figure 5. NH3-TPD profiles of catalysts poisoned by different K+ species
圖 6 不同形態鉀鹽負載后催化劑的XPS圖譜. (a) Ti 2p; (b) W 4f; (c) V 2p; (d) O 1s
Figure 6. XPS profiles of catalysts poisoned by different K+ species: (a) Ti 2p; (b) W 4f; (c) V 2p; (d) O 1s
圖 10 鉀鹽對VWTi催化劑的失活機理. (a) K2SO4; (b) K2O; (c) KCl
Figure 10. Deactivation mechanism of kali salts on the VWTi catalyst: (a) K2SO4 ; (b) K2O; (c) KCl
表 1 SCR催化劑化學成分（質量分數）
Table 1. Chemical composition of the SCR catalyst (mass fraction)
% TiO2 SiO2 Al2O3 WO3 V2O5 MgO S 69.12 13.07 3.77 2.55 1.80 0.97 1.26 
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表 2 新鮮和中毒催化劑樣品的物理吸附參數分析
Table 2. Physical adsorption parameters of fresh and poisoned catalysts
Samples BET surface
area/ (m2·g?1)Total pore volume/
(cm3·g?1)Average pore
diameter/ nmFresh 38.25 0.185 19.85 KS 31.80 0.169 21.31 KO 37.29 0.184 20.30 KC 35.36 0.181 21.45
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表 3 不同形態鉀鹽負載后催化劑樣品V元素XPS結果
Table 3. XPS results of V of fresh and poisoned catalyst samples
V 2p Fresh KS KO KC Ebv/eV ω/% Ebv/eV ω/% Ebv/eV ω/% Ebv/eV ω/% V3+ 515.2 12.79 515.2 14.03 515.2 14.42 515.2 15.62 V4+ 516.2 29.40 516.4 37.34 516.3 38.45 516.5 39.21 V5+ 517.2 57.81 517.3 48.62 517.2 47.13 517.3 45.16
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表 4 不同形態鉀鹽中毒的催化劑再生前后XRF分析結果
Table 4. XRF results of the poisoning catalysts before and after regeneration
Element Mass fraction of the corresponding element/% Fresh KC KC?W KC?A KO KO?W KO?A KS KS?W KS?A Ti 42.43 42.49 43.6 44.48 42.54 43.69 44.49 42.36 44.15 44.63 Si 6.11 5.60 6.14 6.06 5.77 6.11 6.05 5.69 5.91 6.03 Al 2.00 1.87 1.99 1.77 1.92 1.98 1.78 1.85 1.89 1.76 W 2.11 2.08 2.07 2.13 2.03 2.07 2.16 2.03 2.16 2.18 S 0.84 0.84 0.32 0.31 0.83 0.32 0.31 1.06 0.32 0.32 V 1.08 1.09 1.08 0.74 1.08 1.1 0.74 1.08 1.13 0.75 Ca 1.37 1.34 1.31 1.26 1.36 1.31 1.28 1.32 1.20 1.26 K 0.17 1.12 0.36 0.16 0.80 0.30 0.13 0.94 0.27 0.12
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