Exhaust flue gas from fossil fuel combustion usually contains a large quantity of SO2 and NO. In this paper, a process of simultaneous removal of NO and SO2 by ozone oxidation combined with NaOH absorption was chosen. The main investigations involved O3 decomposition, factors affecting NO oxidation (O3 dosage, reaction temperature, NO initial concentration, and presence of SO2), and NaOH absorption. The results indicated O3 decomposition rate increased as temperature rose and was less affected by initial concentration of O3. The optimal temperature for NO oxidation was 150 °C. NO oxidation efficiency increased with the increase of O3 dosage at a fixed temperature. NO initial concentration and the presence of SO2 had a slight effect on NO oxidation. The NO oxidation efficiency remained above 90% when n O3 /n NO was 1. Absorption by NaOH solution resulted in the final removal of above 99% NO, 90% NO2, and nearly 100% SO2 at pH above 11.

The kinetics of sulfite oxidation in the magnesium-based wet flue gas desulfurization (FGD) process were investigated in a stirred bubbling reactor by varying the concentrations of MgSO 3 and MgSO 4 , pH, air flow and temperature. The reaction was found to be 0.88 order with respect to magnesium sulfite and the oxidation could reach the maximum rate when the pH value was close to 6.5. The mechanism of the oxidation was discussed, and it was concluded that the oxidation is controlled by diffusion of oxygen. These results would be useful for the design or process optimization of the magnesium-based wet FGD system.

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Article Highlights• Simultaneous removal of SO 2 and NO x was achieved by oxidation of NO with O 3 and ammonia absorption • The appearance of SO 2 in fuel gas has little impact on the oxidation of NO • The O 3 /NO molar ratio is the most important factor in the ozone oxidation process • Increasing of O 3 /NO mole ratio and SO 2 concentration are favorable to recycling the byproducts Abstract A process for simultaneous desulfurization and denitrification is proposed, consisting of ozone as the oxidizing agent for NO and ammonia solution as the absorbent. The results showed that the presence of SO 2 and the concentration changes of NO and SO 2 have little impact on the oxidation of NO, the oxidation efficiency of NO can achieve over 90% when the molar ratio of O 3 /NO is 1.0. The presence of NO x had little effect on the absorption of SO 2 , while an appropriate increase of SO 2 concentration favorably affected NO x absorption. The removal efficiency of SO 2 and NO x reached 99.34 and 90.01% at pH 10, flow rate 0.95 Nm 3 /h, n[O 3 ]/n[NO] 1.0, initial SO 2 concentration 2000 mg/Nm 3 , initial NO concentration 200 mg/Nm 3 , ammonia concentration 0.3%, oxygen content of the simulated flue gas 12%, oxidation reaction temperature 423 K and absorption reaction temperature 298 K in the experimental system.