CO脱硝的双氛围解耦重组及其温度/反应域场协同机制

During NO reduction by CO, the preference for reaction conditions is contradicting among the different reaction steps. NOx adsorption prefers lower temperature and higher oxygen concentration, while NOx reduction by CO prefers higher temperature and lower oxygen concentration. We proposed a novel process to solve this problem. In this project, the reaction conditions of both temperature and oxygen concentration are reset into the decoupled adsorption-reduction process. This process also integrates air preheating process and is achieved in a rotary reactor. It works like this: in the adsorption zone cold catalysts adsorbs NOx from the oxygen-excess flue gas; the heated catalysts then catalyze the NO+CO reaction in the reduction zone, where excess CO and no oxygen in present; the catalyst are finally cooled down in the air zone with the heat transferred to the air. In this reactor, adsorption is set to the flue gas zone with lower temperature and higher oxygen concentration, while reduction is set to the reduction zone with higher temperature and lower oxygen concentration. Thus the conversion efficiency of CO+NO reaction could be guaranteed. Heat transfer could also be achieved at the same time. In this project we propose to the dynamic process of NOx adsorption-reduction and the reaction mechanism on the catalyst surface, indicating how adsorption, desorption, oxidation and reduction compete with each other during the changing of both temperature and oxygen conditions. The temperature and reaction field also interact with each other. We propose to develop some parameter to characterize this synergetic process. It could also help to further develop other novel NO reduction technologies.

以CO为还原剂的脱硝过程中不同反应步骤对氛围的倾向性相反，NOx吸附倾向于低温高氧的氛围，CO还原NOx则需要高温低氧的氛围。本项目针对温度和氧气双氛围进行吸附和还原的解耦重组，同时耦合空气预热过程，在回转式反应器内实现了蓄热/脱硝的协同过程：吸附区，冷催化剂吸附含氧烟气中的NOx并被烟气加热；还原区，高温CO进一步加热催化剂并还原所吸附的NOx；空气区，空气冷却催化剂并回收热量。将吸附设置于低温高氧的烟气区，还原设置于高温低氧的还原区，可提高整体脱硝效率，且兼顾了烟气的热量回收。本项目拟研究NOx吸附还原的解耦特性及催化剂表面的动态反应机制，阐释温度/氧气等氛围瞬变下吸附、脱附、氧化还原反应之间的共存竞争机制和平衡关系。基于变温/变氛围解耦脱硝过程中温度场和反应域的相互影响，通过对特征参数的剥离和重组，建立温度场和反应域耦合的域场协同机制，为协同脱硝技术奠定理论基础。

以CO为还原剂的脱硝过程中不同反应步骤对氛围的倾向性相反，NOx吸附倾向于低温高氧的氛围，CO还原NOx则需要高温低氧的氛围。本项目针对温度和氧气双氛围进行吸附和还原的解耦重组，同时耦合空气预热过程，在回转式反应器内实现了蓄热/脱硝的协同过程：吸附区，冷催化剂吸附含氧烟气中的NOx并被烟气加热；还原区，高温CO进一步加热催化剂并还原所吸附的NOx；空气区，空气冷却催化剂并回收热量。将吸附设置于低温高氧的烟气区，还原设置于高温低氧的还原区，可提高整体脱硝效率，且兼顾了烟气的热量回收。本项目设计旋转式NOx脱除和空气预热综合反应器（INA），提出一种新的脱硝工艺。本项目对电厂旋转式空气预热器进行温度模拟，在模型基础上得到INA反应器的传热模型，探究蓄热过程。搭建了空气预热器协同低温CO解耦脱硝试验台，实现INA反应器的实际模型，制备催化剂在该试验台上测试NOx脱除活性，探究反应过程。最后对效率好的CuO2 / Fe2O3-CeO2催化剂，利用傅里叶原位红外光谱完成对整个INA反应器蓄热-反应过程的机理探究。探究发现，优选慢速旋转以保持不同区域之间的温度差异，这有利于NOx吸附-还原过程。对于还原性气体，优选向下的流动方向，较高的温度和较大的流速。传热性能对区域分布不敏感，但各区域停留时间对温度分布更加重要。本项目通过加热炉温度控制装置使试验台反应器内温度变化与INA反应器模拟温度一致，，NOx脱除效率超过90%。通过傅里叶原位红外光谱仪的探究，NOx以硝酸盐的形式存储在吸附区，在还原区可以通过高温和CO迅速分解，从而使催化剂容易且深度再生。温度升高以及CO的脱附还原作用对于催化剂再生过程至关重要，并且是NOx脱除性能的关键。本项目应对一氧化碳脱硝中对气氛与温度的矛盾需求，提出并设计了INA反应器，实现了NOx吸附与NOx还原的高效分布进行，也对烟气余热进行利用。研究了系统的传热/反应耦合协同效应，对蓄热/脱硝的工艺过程打下理论基础。