The simultaneous removal of SO₂ and NO_x from sintering flue gas with hydrated lime under low-temperature

The elimination of sulfur oxides (SO₂) and nitrogen oxides (NO_x) from the sintering flue gas is a key chanllenge in pollutant treatment for the iron and steel industry. Using digested quicklime (Ca(OH)₂) as an adsorbent, this study systematically investigated the effects of temperature, relative humidity, SO₂ concentration, NO₂ concentration, CO₂ concentration, and O₂ concentration on the SO₂ and NO_x removal process under ultra-low emission conditions. The growth mechanisms of sulfate and nitrate, along with the phase evolution mechanism, were elucidated. Sulfate formed as a superficial layer on the adsorbent surface, gradually connecting to form a dense barrier. This led to a sharp decrease in BET surface area, pore volume, and pore size, ultimately causing adsorbent exhaustion. In contrast, the products of NO₂ removal exhibited an inward growth model, forming small holes and cracks on the adsorbent surface. The mechanism underlying the significant simultaneous increase in quicklime consumption and CaCO₃ formation in the products during the transition from low-emission to ultra-low emission standards for SO₂ and NOₓ reduction was clarified.