Oxidation and absorption of nitric oxide in a packed tower with sodium hypochlorite aqueous solutions

AbstractThe oxidation and absorption of nitric oxide (NO) with sodium hypochlorite aqueous (NaClO) solutions were studied to develop a two‐stage chemical scrubbing system for NOx control. In the second stage, the most practical medium for NO2 absorption is sodium sulfite aqueous solution. Although a few two‐stage systems have been installed, there are major gaps in developing NaClO aqueous solutions for NO oxidation in the first stage. Of particular importance is the lack of reliable information on rates of the chemical oxidation. A pilot‐scale research program is initiated to evaluate the oxidation rate of NO with NaClO aqueous solutions in a packed tower. The research is directed toward obtaining the height of a transfer unit (HTU) for NO oxidation and acquiring reasonable operating conditions for the packed‐bed scrubbing system. At pH 5.3, NaClO is an excellent scrubbing medium. The results are consistent with hypochlorous acid (HClO) being the oxidizing agent in the solution. The results also indicate that the liquid mass flow rate is a minor parameter that affects the NO oxidation and absorption in the scrubber. A NaClO concentration of >0.8% is crucial for high NO oxidation. © 2005 American Institute of Chemical Engineers Environ Prog, 2005