Using excess O3 to facilitate the NO2 absorption in a sulfite solution: Process conditions and mechanism

Excess O 3 is invariably used to ensure the effective oxidation of NO in the industrial simultaneous desulfurization and denitration through combined ozone oxidation and absorbent scrubbing. O 3 is difficult to fully react with NO considering the short residence time of flue gas , remaining O 3 transport into the subsequent absorption device, and even its escape into the atmosphere. To study the influence of excess O 3 on NO 2 absorption in sulfite solution, we simulated an integrative process of pre-oxidation and post-absorption. NO 2 removal efficiency was improved from 36.1% to 66.5% as the mole ratio of O 3 /NO increased from 1.0 to 1.6. Additionally, the effects of temperature, pH, and reactant concentration with the remaining O 3 on NO 2 removal were evaluated. After 5 h of steady absorption, the concentration of total N species in the adsorbent was 82.8 mmol/L at a O 3 /NO mole ratio = 1.6. However, this concentration was only 51.4 mmol/L at a O 3 /NO mole ratio = 1.0, indicating that more NO 2 was absorbed, and the gas-liquid transfer of NO 2 was enhanced by the excess O 3 via oxidizing NO 2 − into NO 3 − . This work contributes to re-utilizing remaining O 3 and reducing O 3 escape in simultaneous desulfurization and denitration technology.