Deep oxidation of NO via catalytic ozonation
Creators: name: Ko, Li Si
name: Pan, Kuan Lun
name: Chang, Moo Been
Publisher: name: Taylor & Francis
Year: 2024
Subjects: Space Science
Medicine
Environmental Sciences not elsewhere classified
Chemical Sciences not elsewhere classified
Biological Sciences not elsewhere classified

description: In addition to selective catalytic reduction (SCR) and selective non-catalytic reduction (SNCR) which are available to remove NO<sub>x</sub> from flue gas, oxidation method is receiving more and more attention because this method makes it possible to remove NO<sub>x</sub> and SO<sub>2</sub> from flue gas simultaneously by wet scrubbing. O<sub>3</sub> as a strong oxidant has a high oxidation capacity and it can oxide NO to N<sub>2</sub>O<sub>5</sub> which has a higher water solubility compared with NO<sub>2</sub>. However, it needs a long reaction time and the escape of unreacted ozone may cause secondary pollution. In this study, FeMnCo/Al<sub>2</sub>O<sub>3</sub> catalyst and FeMnCe/Al<sub>2</sub>O<sub>3</sub> catalyst were prepared and applied to enhance the deep oxidation of NO<sub>x</sub> with ozone and reduce O<sub>3</sub> slip. Effects of various operating parameters such as O<sub>3</sub>/NO ratio, gas residence time, and operating temperature were evaluated, and the results demonstrate that N<sub>2</sub>O<sub>5</sub> began to generate when O<sub>3</sub>/NO ratio was higher than 1.0 and increased with increasing O<sub>3</sub>/NO ratio. Little residual O<sub>3</sub> was formed in the presence of catalyst, while 350 ppm O<sub>3</sub> was measured at the outlet gas when O<sub>3</sub>/NO ratio was controlled at 2.0. The N<sub>2</sub>O<sub>5</sub> conversion efficiency increased with increasing gas residence time and operating temperature, and the highest N<sub>2</sub>O<sub>5</sub> conversion efficiency was achieved at 100°C. Furthermore, the conversion efficiency remained around 90% during 20 h operation over FeMnCe/Al<sub>2</sub>O<sub>3</sub> catalyst with an O<sub>3</sub>/NO ratio of 1.73, a gas residence time of 1.2 s, and a temperature of 100°C. On the other hand, the N<sub>2</sub>O<sub>5</sub> conversion efficiency remained around 80% during 3 h operation over FeMnCo/Al<sub>2</sub>O<sub>3</sub> catalyst. Overall, FeMnCe/Al<sub>2</sub>O<sub>3</sub> catalyst reveals good potential for deep oxidation of NO by O<sub>3</sub> and can be further developed as a viable catalyst for reducing NO emission from industries. <i>Implications</i>: In this study, FeMnCo/Al<sub>2</sub>O<sub>3</sub> catalyst and FeMnCe/Al<sub>2</sub>O<sub>3</sub> catalyst were applied to enhance the deep oxidation of NO into N<sub>2</sub>O<sub>5</sub> with O<sub>3</sub>. The catalysts can improve the conversion of NO into N<sub>2</sub>O<sub>5</sub>, shorten the reaction time and reduce the unreacted O<sub>3</sub> slip, which are beneficial to reduce the size of the reactor required and cost of APCDs (air pollution control devices) in practical application. This method can make it possible to simultaneously remove NO<sub>x</sub> and SO<sub>2</sub> from flue gas by wet scrubbing for reducing NO emissions from industries, especially small and medium scaled industries, to meet increasingly stringent emission standards.