Wet oxidation and absorption procedure for NOx removal

The removal of NO x with low oxidation degree, low temperature, and high vapor content from small coal-fired boiler emission through selective catalytic reduction is difficult. This study investigated liquid oxidation and absorption to remove NO x systematically. Thermodynamic calculation showed that the equilibrium constants of the NO oxidation and NO x absorption reaction are high; thus, NO x treatment by liquid oxidation and absorption is feasible. Four oxidants (NaClO 2 , NaClO, H 2 O 2 , and KMnO 4 ) and four absorbents (Ca(OH) 2 , CaCO 3 , NaOH, and Na 2 CO 3 ) were used to study the reaction mechanism of the oxidation and absorption processes. Results show that NaClO 2 solution is the best oxidant, and the optimum pH value of the oxidation reaction is 5–6. The oxidation degree reaches 100% when the concentration of the NaClO 2 solution is 1.0%, and the oxidation degree can still reach approximately 50% when the concentration is 0.1%. Ca(OH) 2 slurry has the best absorption performance among the four kinds of absorbents. The NO x removal efficiency of Ca(OH) 2 slurry can reach approximately 70% when the oxidation degree is 50%. The removal efficiency is up to 80% when the oxidation degree is 100%.