Investigation of Ultraviolet Light-Enhanced $H_2{O}_2$ Oxidation of ${\mathrm{NO}}_x$ Emissions

Injecting aqueous solutions of hydrogen peroxide $\left(H_2{O}_2\right)$ into hot flue gases can convert nitric oxide (NO) to higher oxidation states $({\mathrm{NO}}_2\text{,}$ ${\mathrm{HNO}}_2\text{,}$ and ${\mathrm{HNO}}_3)\text{,}$ which can then be removed in a wet scrubber. The optimum temperature for such conversion is 500°C (930°F), at which $H_2{O}_2$ is thermally “activated” (split into free radicals). At lower temperatures ultraviolet (UV) light can be used to activate the peroxide molecules. In this pilot plant study at Kennedy Space Center, experiments were done with none, one, or two UV lamps on, with and without ${\mathrm{SO}}_2$ present in the flue gases, at various temperatures, and with various injection rates of peroxide. Temperatures ranged from 117 to 350°C (243 to 660°F), and the molar ratios (peroxide to ${\mathrm{NO}}_x)$ ranged from 0.68 to 5.02. Conversions of NO varied from below 10 to above 70%, with the highest conversions occurring with higher temperatures, higher dosages of hydrogen peroxide, and with both UV lamps turned on. Conversions of ${\mathrm{NO}}_x$ $(\mathrm{NO}+{\mathrm{NO}}_2)$ varied from below 5 to above 40%. The presence of ${\mathrm{SO}}_2$ did not inhibit NO or ${\mathrm{NO}}_x$ conversion.