Experimental Research Of Desulfurization And Denitrification By Liquid Phase Oxidation With Fenton-like Agent

NOxand SO₂produced from coal combustion are the main atmosphericpollutants of our country, which will have a noticeably negative impact onenvironment if could not be handle properly. Nowadays, the most popular technologyin flue gas desulfurization and denitrification is wet lime/limestone gypsum flue gasdesulfurization （FGD） combining selective catalytic reduction method （SCR）.However, this method need two technologies and devices, in addition, high cost.Therefore, simultaneous desulfurization and denitrification technology has moreadvantages and broader application prospects.Fenton reaction as a kind of advanced oxidation processes （AOPs） has beenprevalent in the control of atmospheric pollutants. Nevertheless, it is rarely reportedin literatures about Fenton-like reagent (Fe³⁺/H₂O₂). The present work was devoted topurify coal-fired flue gas containing SO₂and NO using Fenton-like reagent. Thereaction process of Fenton-like reaction was summarized. Fenton-like reaction andaqueous catalytic oxidation of Fe（III） in desulfurization and denitrification werediscussed. The relationship between Fenton-like reaction and aqueous catalyticoxidation was also investigated. The experiments of separate denitrification andsimultaneous desulfurization and denitrification were conducted in a self-made bubblecolumn reactor. Separate denitrification experiments were carried out by changingH₂O₂concentration, Fe³⁺dosage, initial pH value, gas flow, different light conditions,H₂O₂dosing way and NO inlet concentration. Simultaneous desulfurization anddenitrification experiments were conducted by different SO₂inlet concentration, H₂O₂concentration, Fe³⁺concentration, initial pH value, gas flow, and light conditions.Finally, the best reaction conditions of single factor were obtained for separatedenitrification and simultaneous desulfurization and denitrification.In separate denitrification experiments, an increase on H₂O₂concentration wouldincrease NO removal efficiency; when H₂O₂concentration was0.5mol/L, more Fe³⁺presented was favor for NO removal, the best denitrification efficiency was obtainedat [H₂O₂]/[Fe³⁺]=6; The optimum initial pH value was3; NO removal efficiencydecreased with increasing gas flow; Employing UV irradiation could raise NOremoval efficiency; Adding H₂O₂for three times was benefit for NO removal, whichcould make separate denitrification efficiency maintained at about80%. The denitration efficiency decreased with the increase of NO inlet concentration.In the simultaneous desulfurization and denitrification experiments, the influenceof different factors on simultaneous desulfurization and denitrification are describedas following: SO₂inlet concentration had great impact on NO removal efficiency. Themore H₂O₂existed, the better efficiency of denitrification and desulfurization. WhenH₂O₂concentration was over0.5mol/L, the efficiency of denitrification anddesulfurization changed indistinctively with the increase of H₂O₂concentration. WhenH₂O₂concentration was0.5mol/L, the increase of Fe³⁺dosage could improve theefficiency of denitrification, and have little effect on desulfurization. The bestdenitrification obtained when initial pH was3, while the initial pH had relativelyweak effect on the removal of SO₂. Desulfurization and denitrification efficiencydropped significantly with the increase of gas flow. Adding two UV lamps couldsignificantly improve the efficiency of denitrification, but it had no significant effecton the desulfurization efficiency.SO₂in water is more soluble than NO, which makes SO₂easier to be removed.SO₂will consume a large amount of absorbent. Sulfate generated by SO₂was notconducive for Fenton-like reaction. As a result, NO removal efficiency decreasedsignificantly with SO₂presented. Fenton-like reaction and the liquid phase catalyticoxidation of Fe（III） had a synergistic effect on desulfurization and denitrification.The capability of Fenton-like reagent in individual denitrification andsimultaneous desulfurization and denitrification was studied, which was preliminaryresearch for practical application and provided a basis for subsequent related research.