Removal of NO from flue gas by aqueous chlorine-dioxide scrubbing solution in a lab-scale bubbling reactor

The present study attempts to clean up nitric oxide from the simulated flue gas using aqueous chlorine-dioxide solution in the bubbling reactor. Chlorine-dioxide is generated by chloride-chlorate process. Experiments are carried out to examine the effect of various operating variables like input NO concentration, presence of SO2, pH of the solution and NaCl feeding rate on the NOx removal efficiency at 45 °C. Complete oxidation of nitric oxide into nitrogen dioxide occurred on passing sufficient ClO2 gas into the scrubbing solution. NO is finally converted into nitrate and ClO2 is reduced into chloride ions. A plausible reaction mechanism concerning NOx removal by ClO2 is suggested. DeNOx efficiency increased slightly with the increasing input NO concentration. The presence of SO2 improved the NO2 absorption but pH of solution showed marginal effect on NO2 absorption. NOx removal mechanism changed when medium of solution changed from acidic to alkaline. A constant NOx removal efficiency of about 60% has been achieved in the wide pH range of 3-11 under optimized conditions.