Nitric oxide removal by combined urea and FeEDTA reaction systems.

(NH)CO as well as FeEDTA is an absorbent for simultaneous desulfurization and denitrification. However, they have their own drawbacks, like the oxidation of FeEDTA and the low solubility of NO in urea solution. To overcome these defects, A mixed absorbent containing both (NH)CO and FeEDTA was employed. The effects of various operating parameters (urea and FeEDTA concentration, temperature, inlet oxygen concentration, pH value) on NO removal were examined in the packed tower. The results indicated that the NO removal efficiency increased with the decrease of oxygen concentration as well as the increase of FeEDTA concentration. The NO removal efficiency had little change with a range of 25-45 °C, and sharply decreased at the temperature of above 55 °C. The NO removal efficiency initially increases up to the maximum value and then decreases with the increase of pH value as well as the raise of urea concentration. In addition, the synergistic mechanism of (NH)CO and FeEDTA on NO removal was investigated. Results showed that urea could react with FeEDTA-NO to produce FeEDTA, N, and CO, and hinder oxidation of FeEDTA. Finally, to evaluate the effect of SO on NO removal, a mixed absorbent containing FeEDTA, urea, and NaSO was employed to absorb NO. The mixed absorbent could maintain more than 78% for 80 min at 25 °C, pH = 7.0, (NH)CO concentration of 5 wt%, FeEDTA concentration of 0.02 M, O concentration of 7% (v/v), and NaSO concentration of 0.2 M.