Simultaneous Removal of NO_xand SO₂through the Combination of Sodium Chlorite Powder and Carbon-based Catalyst at Low Temperature

Abstract

NO oxidation is an important prerequisite step to assist the selective catalytic reduction (SCR) at low temperatures (<200°C). Therefore, we conducted the lab-and bench-scales experiments appling the sodium chlorite powder (NaClO2(s)) for the oxidation of NO to NO2 and the carbon-based catalyst for the reduction of NOx and SO2; the lab-and bench-scales experiments were conducted in laboratory and iron-ore sintering plant, respectively. In the lab-scale experiment, known concentrations of NOx (200 ppm), SO2 (75 ppm), H2O (10%) and NH3 (400 ppm) in 2.6 L/min were introduced into a packed-bed reactor containing NaClO2(s), then gases produced by the reaction with NaClO2(s) were fed into the carbon-based catalyst (space velocity = 2,000 hr-1) at 130°C. In the bench-scale experiment, flue gases of 50 Nm 3 /hr containing 120 ppm NO and 150 ppm SO2 were taken out from the duct of iron-ore sintering plant, then introduced into the flow reactor; NaClO2(s) were injected into the flow reactor using a screw feeder. Gases produced by the reaction with NaClO2(s) were introduced into the carbon-based catalyst (space velocity = 1,000 hr-1). Results have shown that, in both lab-and bench-scales experiments, NO was oxidized to NO2 by NaClO2(s). In addition, above 90% of NOx and SO2 removal were obtained at the carbon-based catalyst. These results lead us to suggest that the combination of NaClO2(s) with the carbon-based catalyst has the potential to achieve the simultaneous removal of NOx and SO2 at low temperature (<200°C).