Simultaneous Removal Of SO₂ And NO_x By Fenton Oxidation

Coal-fired power plant has been proven to be a major anthropogenic source of various air pollutants emissions.SO₂ and NO_x in coal-fired flue gas are the main pollutants in the atmosphere of our country,which will have a noticeably negative impact on environment and human body if could not be handled properly.Nowadays,the most popular technology in flue gas desulfurization and denitrification is wet lime/limestone gypsum desulfurization technology（WFGD）combined selective catalytic reduction（SCR）.However,this method needs two technologies and devices,which caused the cost of investment and operation is relatively large.Therefore,it is of great theoretical and practical significance to develop an integrated technology of desulfurization and denitrification at the same time.Based on the researches in the field of pollutants of advanced oxidation technology（AOPs）at home and abroad,this paper proposed Fenton oxidation method to remove SO₂and NO_x in coal-fired flue gas simultaneously.The hydroxyl radical（·OH）produced by Fenton has extremely high oxidization,which has the characteristics of low selectivity,low cost and no secondary pollution,showing good potential for application.Firstly,the effect of flue gas temperature(T_gas),Fenton reagent temperature(T_liq),initial pH value,NO initial concentration(C⁰_NO),gas flow and[Fe²⁺]/[H₂O₂]on the oxidation efficiency of NO were investigated in a self-designed reactor.Secondly,explored the effects of various flue gas components（O₂,CO₂ and SO₂）on NO oxidation efficiency under different concentrations,and explored the efficiency and mechanism of Fenton simultaneous desulfurization and denitrification.Thirdly,the prediction model was established by the response surface methodology,and the interaction between various factors and the influence on NO oxidation efficiency were analyzed,and the optimal reaction conditions were simulated.Finally,because of high content of component in coal-fired flue gas mixed in Fenton system was studied and analyzed the influence of anions(SO₄^2-,Cl^-,NO₃^-)and cation(Ca²⁺,Mg²⁺and Na⁺)on NO oxidation efficiency.The results showed that the optimum removal conditions were obtained as T_gas=70 ^oC,T_liq=25 ^oC,Gas flow=600 mL/min,C⁰_NO=982 mg/m³（800 ppm）,initial pH=3,[Fe²⁺]/[H₂O₂]=0.05:1,respectively.And the oxidation efficiency of NO was 62.69%under this conditions.The oxidation efficiency of NO was the highest when the volume fraction of O₂ is 5%.CO₂ had obvious inhibitory effect on the oxidation efficiency of NO.There was competition of oxidant between SO₂ and NO.When simultaneous desulfurization and denitrification with Fenton system,with the increasing of SO₂ concentration,NO oxidation efficiency decreased slightly,and kept in the 50⁶0%.The second-order polynomial model established by the response surface method had high fitting degree,which can simulate and predict the response value effectively.The optimal conditions were in accordance with the experimental results.The oxidation efficiency of NO under the optimized condition was74.16%,which is about 12%higher than the experimental value.With the increasing of the concentration of anion and cation,the oxidation efficiency of NO decreased.When the concentration is 0.01 mol/L,NO₃^-and Mg²⁺can promote the improvement of NO oxidation efficiency obviously.The research results of this paper have a certain theoretical guiding effect on desulfurization and denitrification by Fenton oxidation process in industrial application.