Wet oxidation of NO with NaClO2 in alkaline conditions: effects of acidic components in flue gas.

Excessive ClO2 tends to be produced and escape, causing secondary pollution when wet oxidation of NO with NaClO2 is conducted under acidic conditions. NaClO2 alkaline oxidation has accordingly received a wide attention. In this work, NaClO2 alkaline oxidation of NO has been systematically studied in a self-built spray tower. Focus has been placed on the effects of acidic components contained in flue gas such as CO2, HCl and SO2. ClO2 and HClO2 are considered more effective for NO oxidation, which tend to be produced in an acidic environment. HCO3- has a relatively higher hydrolysis coefficient than ClO2-, leading to more HClO2 formation. Similarity is found with HCl although the effect is not as significant as CO2 due to its low concentration in flue gas. SO2 exhibits a negative effect on NO removal since HClO2 can be consumed by SO2. Nearly 100 % NO removal efficiency can be achieved although there is an initial time delay necessary for the neutralization of alkaline environment. A similar performance has been observed for HCl. On the contrary, SO2 exhibits a negative effect on NO removal due to the competition with NO in the consumption of NaClO2. Additives such as NaClO and CTAC were also used to enhance NaClO2 alkaline oxidation performance. Interesting to note that CTAC can nearly eliminate the time delay by intensifying the gas-liquid mass transfer.