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

Area of Science:

• Environmental Engineering
• Chemical Engineering
• Materials Science

Background:

• Flue gas desulfurization (FGD) and denitrification (DeNOx) are critical for air pollution control.
• Simultaneous removal processes are sought for efficiency and cost-effectiveness.
• Steel slag, a waste material, offers potential as a reagent in environmental applications.

Purpose of the Study:

• To investigate the simultaneous removal of sulfur dioxide (SO2) and nitrogen oxides (NOx) using steel slag slurry and ozone (O3) oxidation.
• To evaluate the influence of key operational parameters on removal efficiencies.
• To elucidate the reaction mechanisms and product compositions.

Main Methods:

• Laboratory-scale wet flue gas desulfurization experiments.
• Variations in oxidation temperature, steel slag concentration, initial SO2 concentration, and pH.
• Analysis of aqueous solution and solid residue compositions, including nitrogen balance.

Main Results:

• Optimal NOx removal efficiency (~96%) achieved at 90°C oxidation temperature; higher temperatures decreased efficiency due to N2O5 decomposition.
• Denitrification efficiency was stable between pH 8.5 and 4.5.
• SO2 concentration had a complex effect: low concentrations (500 ppm) promoted NO2 absorption, while higher concentrations led to competitive absorption.

Conclusions:

• Steel slag slurry combined with ozone oxidation is a viable method for simultaneous SO2 and NOx removal.
• Nitrate (NO3-) and sulfate (SO42-) were identified as major products in the aqueous phase.
• The proposed reaction mechanism involves the transformation of nitrogen and sulfur compounds, with CaSO4 and FeO as primary solid residues.