Wet oxidation and absorption procedure for NOx removal

The removal of NOx 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 NOx systematically. Thermodynamic calculation showed that the equilibrium constants of the NO oxidation and NOx absorption reaction are high; thus, NOx treatment by liquid oxidation and absorption is feasible. Four oxidants (NaClO2, NaClO, H2O2, and KMnO4) and four absorbents (Ca(OH)(2), CaCO3, NaOH, and Na2CO3) were used to study the reaction mechanism of the oxidation and absorption processes. Results show that NaClO2 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 NaClO2 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 lands of absorbents. The NOx 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%. (C) 2018 Elsevier B.V. All rights reserved.