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摘要: 研究了丙烯在金属铁作用下还原NO的特性。采用陶瓷管流动反应器在300-1100℃研究了不同条件下的NO还原效率，考察了SO2的影响，采用XRD、SEM和EDS分析了反应后金属铁表面的组分和微观结构特征。结果表明，丙烯在金属铁作用下具有良好的NO还原效果。在N2气氛，温度超过800℃后，金属铁作用下丙烯还原NO的效率达到了95%以上。在模拟烟气、富燃料条件下，温度高于900℃时，丙烯与金属铁还原NO的效率超过了90%。SO2对丙烯在金属铁作用下还原NO的效率影响很小。机理分析表明，当丙烯与金属铁共同还原NO时，一方面，NO被金属铁直接还原，同时丙烯还原氧化铁为金属铁；另一方面，丙烯通过再燃机理还原NO，同时再燃中间产物被氧化铁氧化为N2。Abstract: NO reduction by propene with iron was experimentally studied. NO reduction efficiency at different conditions was tested in a flow-type ceramic tube reactor at 300-1100℃. The effect of SO2 was also investigated. XRD, SEM and EDS techniques were used to analyze the composition and surface microstructure of the iron sample after reaction. Results showed that propene was effective to reduce NO with iron. More than 95% of NO was reduced above 800℃ in N2 atmosphere and more than 90% of NO was reduced above 900℃ at fuel-rich conditions in simulated flue gas atmosphere by propene with iron respectively. SO2 had minor effect on NO reduction. The analysis on reaction mechanism showed that when propene was used to reduce NO with iron, on one hand, NO was directly reduced by iron while propene reduced the iron oxides to iron; on the other hand, propene reduced NO via reburning reaction while the re-burning intermediates were oxidized by iron.
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Key words:
- combustion emission control /
- flue gas deNOx /
- C3H6 /
- iron
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图 2 在N2氛围中C3H6-Fe还原NO时生成的CO含量
Figure 2 Exit CO when propene reducing NO over iron in N2 atmosphere
(flow rate 2 L/min, φNO=0.05%,φC3H6=0.1%-0.3%, in N2 base) ■: φC3H6=0.1%; ●: φC3H6=0.2%; ▲: φC3H6=0.3%; □: φC3H8=0.1%; ○: φC3H8=0.2%
图 3 在N2氛围中0.2% C3H6还原NO后铁样品的SEM照片和XRD谱图
Figure 3 SEM image (a) and XRD pattern (b) of the iron after reducing NO with 0.2% C3H6 in N2 atmosphere
(flow rate 2 L/min, φNO=0.05%, φC3H6=0.2%, in N2 base)
图 4 在N2氛围中0.1%C3H6还原NO后铁样品的SEM照片和XRD谱图
Figure 4 SEM image (a) and XRD pattern (b) of the iron after reducing NO with 0.1% C3H6 in N2 atmosphere
(flow rate 2 L/min, φNO=0.05%, φC3H6=0.1%, in N2 base)
图 5 N2氛围下φC3H6为0.2%作用下铁还原NO后铁样品EDS检测照片
Figure 5 Detection image of EDS over iron surface after reducing NO with φC3H6=0.2% in N2 atmosphere
(flow rate 2 L/min, φNO=0.05%, φC3H6=0.2%, in N2 base)
图 6 模拟烟气条件下C3H6-Fe还原NO的效率
Figure 6 NO reduction by propene over metallic iron in simulated flue gas atmosphere
(flow rate 2 L/min, φO2=2.0%,φCO2=17.0%, φNO=0.05%, in N2 base)
■: SR1=SR2=0.7; □: SR1=0.7, SR2=1.2;●: SR1=SR2=0.8; ○: SR1=0.8, SR2=1.2;
▲: SR1=SR2=0.9; △: SR1=0.9, SR2=1.2;
▼: SR1=SR2=1.0; ∇: SR1=1.0, SR2=1.2;
◀: SR1=SR2=1.1; ◁: SR1=1.1, SR2=1.2;▶: SR1=SR2=1.2
图 7 模拟烟气条件下有、无铁时C3H6还原NO的效率对比
Figure 7 Comparison of NO reduction by propene with and without iron in simulated flue gas atmosphere
(flow rate 2 L/min, φO2=2.0%, φCO2=17.0%, φNO=0.05%, in N2 base)
■: with iron, SR1=0.7, SR2=1.2;
□: without iron, SR1=0.7, SR2=1.2;
●: with iron, SR1=0.9, SR2=1.2;
○: without iron, SR1=0.9, SR2=1.2;
▲: with iron, SR1=1.0, SR2=1.2;
△: without iron, SR1=1.0, SR2=1.2;
▼: with iron, SR1=1.2, SR2=1.2;
∇: without iron, SR1=1.2, SR2=1.2
图 8 模拟烟气条件下金属铁作用下C3H6与C3H8还原NO的效率对比
Figure 8 Comparison of NO reduction by propene and propane with iron in simulated flue gas atmosphere
(flow rate 2 L/min, φO2=2.0%, φCO2=17.0%, φNO=0.05%, in N2 base)
■: C3H6, SR1=0.7, SR2=1.2;
□: C3H8, SR1=0.7, SR2=1.2;
●: C3H6, SR1=0.9, SR2=1.2;
○: C3H8, SR1=0.9, SR2=1.2;
▲: C3H6, SR1=1.0, SR2=1.2;
△: C3H8, SR1=1.0, SR2=1.2;
▼: C3H6, SR1=1.2, SR2=1.2;
∇: C3H8, SR1=1.2, SR2=1.2
图 9 模拟烟气条件下SO2对金属铁作用下C3H6还原NO效率的影响 (SR1=0.9)
Figure 9 Effect of SO2 on the reduction of NO by propene over iron in simulated flue gas atmosphere
(flow rate 2 L/min, φO2=2.0%, φCO2=17.0%, φNO=0.05%, φSO2=0-0.04%, in N2 base)
■: φSO2=0, SR2=1.2;
□: φSO2=0, SR2=0.9;
●: φSO2=0.01%, SR2=1.2;
○: φSO2=0.01%, SR2=0.9;
▲: φSO2=0.02%, SR2=1.2;
△: φSO2=0.02%, SR2=0.9;
▼: φSO2=0.04%, SR2=1.2;
∇: φSO2=0.04%, SR2=0.9表 1 N2氛围中φC3H6为0.2%作用下铁还原NO后铁样品EDS表征
Table 1 EDS results over iron surface after reducing NO with φC3H6=0.2% in N2 atmosphere
Image 1 Image 2 element w/% atomic percent watom/% element w/% atomic percent watom/% C 2.60 9.08 C 3.86 12.38 O 9.65 25.22 O 12.36 29.78 Fe 87.75 65.71 Fe 83.78 57.84 Total 100.00 100.00 Total 100.00 100.00 
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