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 NO_x 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 NO_x removal by ClO₂ is suggested. DeNO_x 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. NO_x removal mechanism changed when medium of solution changed from acidic to alkaline. A constant NO_x removal efficiency of about 60% has been achieved in the wide pH range of 3–11 under optimized conditions.