Characteristics of reducing NO using urea and alkaline additives

The reduction of nitric oxide using urea solution combined with alkali salt additives has been studied in a flow tube. The inlet concentration of NO was 500 ppm, with airflow rates of 3 and 5 L/min. Reduction of NO was studied from 650 to 1050 °C with urea solutions of 0.3 to 1 mol/L. The efficiency of reduction of NO increased by 44% in the presence of urea alone. A further increase in efficiency was observed in the presence of NaOH as additive; in fact, efficiency increased by more than 25 and 75% when 0.5 and 1 mol/L NaOH, respectively, were added with the urea solution. The efficiency of reduction of NO increased with all additives, but descended in the order NaOH, Na2CO3, NaNO3, HCOONa, and CHCOONa. The maximum efficiencies of NaOH and NaNO3 are 74 and 73%, respectively.