Abstract:

Currently, industrial kilns mainly use vanadium-titanium-based SCR catalysts to control nitrogen oxides (NO _x ) in flue gas. However, the flue gas generated from industrial kilns contains high oxygen content, and the mechanism in the effect of high O₂ content on the SCR reaction process over vanadium-titanium catalyst is still unclear. Therefore, the denitration activity of vanadium-titanium catalysts under different O₂ contents was experimentally studied. The effects of different O₂ contents on the physical and chemical structure of vanadium-titanium catalysts were systematically analyzed by various characterization methods. At the same time, combined with the in-situ infrared technology, the mechanism of SCR denitration reaction of vanadium-titanium catalysts with different O₂ contents was further revealed. The results show that high O₂ content can improve the low-temperature denitration efficiency of vanadium-titanium catalysts to a certain extent at the reaction temperature of 150—400℃. The increase of the vanadium loading can make the denitration activity temperature window expanding and moving to the low temperature region. After the catalyst undergoes NH₃-SCR denitration reaction under different O₂ content conditions, its physical structure almost unchanged. Higher O₂ content during the reaction can accelerate the SCR denitration reaction by promoting the acid cycle and redox cycle on the catalyst surface. The active intermediates NH₃ (L) and \mathrm{N}{\mathrm{H}}_{\mathrm{4}}^{+}^{(B) are consumed faster in the SCR reaction process at higher O₂ content, and high O₂ content can promote the formation of nitrate species and activate the bridge nitrates, thereby enhancing SCR denitration activity of the vanadium-titanium catalyst.}

Key words: industrial kiln, high oxygen concentration, NH₃-SCR reaction, V₂O₅/TiO₂ catalyst, load

摘要：

目前，工业窑炉主要采用钒钛系SCR催化剂对烟气中氮氧化物（NO _x ）进行控制，然而工业窑炉部分工序烟气O₂含量高，且高O₂含量对SCR反应过程的机理影响尚不明确。因此，实验研究了烟气中不同O₂含量下钒钛催化剂的脱硝活性，并采用多种表征方法系统分析了O₂含量对催化剂物理化学结构的影响；同时结合原位红外技术，进一步揭示了不同O₂含量下钒钛催化剂SCR脱硝反应机理。研究表明：在150~400℃的反应温度下，较高O₂含量可一定程度提高催化剂的低温脱硝效率，钒负载量增加可使催化剂脱硝活性温度窗口扩展且向低温区移动；催化剂在不同O₂含量条件下经过NH₃-SCR脱硝反应后，其物理结构变化不明显，反应过程中较高的O₂含量可促进催化剂表面酸循环和氧化还原循环，加速SCR脱硝反应；较高O₂含量使得SCR反应过程活性中间体 NH₃（L）和\mathrm{N}{\mathrm{H}}_{\mathrm{4}}^{+}（B）消耗加快，促进桥型硝酸盐物种的形成，从而提高其SCR脱硝活性。

关键词: 工业窑炉, 高O₂含量, NH₃-SCR反应, 钒钛催化剂, 负载量