微波辐射强化焦炭还原NO的反应机制

Study of microwave enhancement on char reducing NO

摘要:

为探索高效、廉价的燃煤工业锅炉脱硝技术,以适宜工业应用的苹果木热解焦炭和热解兰炭作为NO还原剂,在微波反应系统中研究微波辐射对两种样品还原NO能力的影响,并结合红外测温实验,以及两种样品的孔隙结构、热重反应性等理化性质,对还原实验结果进行分析. 研究结果表明: 和热解兰炭相比,苹果木热解焦炭的孔隙结构更加发达,BET比表面积和孔容积更大,易于着火,燃烧反应速度较早达到最大值,并最先燃尽；但其燃烧剧烈强度、前期反应能力、可燃性以及燃烧性能偏弱. 未施加微波时,苹果木热解焦炭对NO的还原能力强于热解兰炭；施加微波后,两种样品还原NO的能力较未施加微波时均有所增强；微波辐射有效促进了焦炭对NO的还原,且这种促进效果和微波功率成正比关系；微波辐射对热解兰炭的NO还原的促进效果较苹果木热解焦炭明显. 红外测温实验结果表明,经过不同功率的微波辐射后,两种样品表面温度均有不同程度的提高,说明微波具有明显的热效应,促进了焦炭对NO的还原.

Abstract:

To explore a NO reduction technology of coal-fired industrial boilers with high efficiency and low cost, the applewood pyrolysis char and pyrolytic semi-char which are suitable for industrial applications were used as reducing agents, and the effect of microwave on the two samples reducing NO was studied in a microwave reaction system. For explaining the NO reduction experiment results, the infrared temperature measurement experiment, and the physical and chemical properties such as pore structure and TG reactivity was studied. The results show that, compared with the pyrolytic semi-char, the pore structure of applewood pyrolysis char is more developed with higher BET specific surface area and pore volume, it also ignites earlier, the combustion reaction rate reaches its maximum earlier and burns out first. However, its combustion intensity, reaction ability of earlier stage, flammability and combustion performance are weak. When the microwave is not applied, the NO reduction ability of applewood pyrolysis char is stronger than that of pyrolytic semi-char. Both the two samples have better NO reduction ability with microwave applying, and with the increase of microwave power, the NO reduction rate increases. The effect of microwave on pyrolytic semi-char reducing NO is stronger than that of applewood pyrolysis char. Meanwhile, infrared temperature measurement that the surface temperature of two samples both increases confirms that the microwave has an obvious thermal effect which could promote the NO reduction by char.