Simultaneous Removal of SO₂ and NO Using Steel Slag Slurry Combined with Ozone Oxidation

In this work, steel slag slurry was used in combination with O₃ oxidation for the simultaneous removal of SO₂ and NO in a laboratory-scale wet flue gas desulfurization process. The effects of the oxidation temperature, steel slag concentration, initial SO₂ concentration, and pH value on the desulfurization and denitrification efficiencies were studied. The results showed that the highest NO removal efficiency occurred at an oxidation temperature of 90 °C. With an increase of the oxidation temperature above 90 °C, the denitrification efficiency decreased due to the decomposition of N₂O₅. The effect of the SO₂ concentration on denitrification was complicated. When the concentration of SO₂ was 500 ppm, generation of SO₃ ^2- promoted the absorption of NO₂. However, higher SO₂ concentrations strengthened the competitive absorption of SO₂ and NO . In the pH range of 8.5-4.5, the denitrification efficiency was maintained at about 96%. The component analyses of the aqueous solution and the solid residue were conducted to investigate the compositions of the absorption products. The results showed that NO₃ ^- and SO₄ ^2- were the major anions in the aqueous solution. The nitrogen balance was analyzed to be 95.8%, clearly illustrating the migration and transformation path of nitrogen. In the solid residue, most alkaline substances were consumed, and the final products were mainly CaSO₄ and FeO. Accordingly, the reaction mechanism of simultaneous desulfurization and denitrification using steel slag combined with ozone oxidation was proposed.