Sintering/Pellet Gas Ozone Oxidation Combined With SDA Method Sulfur Nitrate Synergistic Control Technology

With the release of ultra-low emission limits in the steel industry,studying the technology for removing SO₂ and NO_x in sintering/pellet flue is very significant for the green development of iron and steel.The technology of O₃ oxidation combined with SDA?spray dryer absorption?is one of the efficient methods for simultaneously removal of SO₂ and NO_x.In this paper,the effects of different parameters on the denitrification efficiency was firstly carried out,including O₃ site,O₃/NO molar ratio,the tower temperature,Ca/?S+2N?molar ratio and slurry flow rate.The reaction mechanism of this technology was put forward by the experimental results and XRD characterization.Subsequently,the effect of Ca SO₃ on the absorption of SO₂ and NO_xunder industrial back mixing was simulated.In order to further improve the removal efficiency of SO₂,the experiment of using calcium-based additives and magnesium-based additives were studied respectively.This paper mainly draws the following conclusions:?1?The yield of N₂O₅ can be increased obviously by selecting O₃ site inside of the tower.It is found that when the O₃/NO molar ratio?1,the oxidation product of NO is NO₂,which promotes the absorption of SO₂,while the generation of N₂O₅ can reduce the desulfurization efficiency as the O₃/NO molar ratio>1.?2?The increase of the tower temperature accelerates the evaporation rate of the absorbent liquid film,which leads to the shortening the reaction time of gas-liquid phase and decreases the desulfurization efficiency.Both the increase of Ca/?S+2N?molar ratio and the slurry flow rate can improve desulfurization efficiency.No matter how high the Ca/?S+2N?molar ratio or slurry flow rate is,the NO₂ cannot be completely removed because the NO₂ in the gas phase cannot be completely dissolved in the slurry.?3?In the experiment of using Ca?OH?₂/Ca SO₃ mixture with different compositions as the absorbent,the addition of Ca SO₃ leads to the decrease of desulfurization efficiency.This is mainly due to a decrease in the Ca?OH?₂ as the effective absorbent.?4?In the experiments of sodium-based and magnesium-based additives,it is found that the alkalinity and solubility are the main factors affecting the desulfurization efficiency.However,these two effects have almost no influence on the denitrification efficiency.This is because when the O₃/NO molar ratio is 1.8,the oxidation product of NO is mainly N₂O₅.Compared with H₂SO₃(Ka₁=1.23×10^-2),H⁺ionized by HNO₃binds OH^-preferentially in the liquid film,which makes HNO₃ dominate in competing OH^-compared with the absorption of SO₂.