Investigation of NO Removal with Ozone Deep Oxidation in Na2CO3 Solution

Wet flue gas desulfurization (WFGD) provides highly efficient SO2 removal in industrial flue gas treatment. Although NO and NO2 are not readily absorbed in the traditional desulfurization wash tower, deep oxidation with ozone can promote the formation of N2O5 that is absorbed in the washing fluid, making possible simultaneous denitration and desulfurization in the WGFD unit. This paper presents a survey of operating parameters for NOx removal after ozone deep oxidation using a Na2CO3-based WFGD. The effects of preoxidation time, Na2CO3 aqueous solution concentration, spray liquid/gas ratio, gas residence time in wash tower, and SO2 concentration on NOx removal efficiency were investigated systematically in a variable-configuration experimental setup. The results demonstrate that preoxidation time was the most sensitive factor in N2O5 formation, although oxidation continued in the wash tower. Thus, one strategy for a system where physical constraints limit the volume of the oxidation chamber is to extend the flue gas residence time in the wash tower. Increasing the liquid/gas ratio and Na2CO3 solution concentration gave some enhancement on the wet absorption process. Under optimal laboratory conditions, 95% NOx removal efficiency was achieved. Addition of SO2 yielded a slight inhibition for NOx removal, and under industrial relevant operating conditions, 98% SO2 and 62% NOx removal was achieved during 50 min experimental runs.