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

Excessive ClO 2 tends to be produced and escape, causing secondary pollution when wet oxidation of NO with NaClO 2 is conducted under acidic conditions. NaClO 2 alkaline oxidation has accordingly received a wide attention. In this work, NaClO 2 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 CO 2 , HCl and SO 2 . ClO 2 and HClO 2 are considered more effective for NO oxidation, which tend to be produced in an acidic environment. HCO 3 − has a relatively higher hydrolysis coefficient than ClO 2 − , leading to more HClO 2 formation. Similarity is found with HCl although the effect is not as significant as CO 2 due to its low concentration in flue gas. SO 2 exhibits a negative effect on NO removal since HClO 2 can be consumed by SO 2 . 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, SO 2 exhibits a negative effect on NO removal due to the competition with NO in the consumption of NaClO 2 . Additives such as NaClO and CTAC were also used to enhance NaClO 2 alkaline oxidation performance. Interesting to note that CTAC can nearly eliminate the time delay by intensifying the gas-liquid mass transfer.