Study On Catalytic Oxidation Of NO_x And SO₂ In Flue Gas By Micro-nano Bubble Coupled Iron Catalyst

As a result of our country's industrial developments,SO₂ and nitrogen oxides?NO_x?emissions are also gradually increased,so our country started to put more restricted rules for the emission limitations regarding the toxic gases limits.Meanwhile,as a results of the imperfect technology and huge industrial base,which result in keeping the level of the toxic gases emission at increasing rate continuously.As the flue gases traditional technologies such as desulfurization and denitration which include,wet methods,dry methods and so on.Which have many drawbacks.It is urgent to develop integrated NO_x and SO₂ removal methods,especially simple and integrated NO_x and SO₂ removal methods while using the available natural resources?such as air and water?.One of the promising technologies that has started to attract many attentions in China and worldwide is micro-nano bubble,which has many advantages include the long stagnation time,large specific area,high mass transfer rate and also strong oxidant.China is among the top counties that has started early to explore this research area and even getting many good results in it.The research group has used micro-nano bubble for the desulfurization and denitration and they have got impressive removal results for both.Starting with SO₂ we have got 100%removal rate,on the other hand for the NO_x removal rate it was acceptable level,they also found that for NO_x removal adding appropriate amount of the transition metals such as Fe²⁺and Mn²⁺in the micro-nano bubble system can promote NO removal rate.But the main drawback is its difficult to remove later which will result in polluted water.So the simultaneous removal of SO₂ and NO_x was studied by using recyclable solid-phase iron catalyst coupled with micro-nano bubble in this research?simulating NO_x with NO bottled gas on the market?.Meanwhile the effects of catalyst dosage,particle size,NaCl concentration,pH and air intake on NO removal were investigated.At the same time the catalysts were characterized by X-ray diffraction?XRD?,scanning electron microscope?SEM?,energy dispersive spectrometer?EDS?and X-ray photoelectron spectroscopy?XPS?,and the mechanism of NO absorption by catalyst was investigated.The deduction were as the following:?1?The addition of iron catalyst in the micro-nano gas-liquid system can promote the generation of hydroxyl radical in the micro-nano bubbles,which will improve the desulfurization and denitrification rate.?2?XRD results indicated that the catalyst surface did not change significantly before and after use.Meanwhile the SEM and EDS results for FeS_x has showed that the surface morphology has become rough after use,but for the Fe₃O₄ surface morphology did not change.After using the two kinds of iron catalysts,the iron content on the surface decreased and the oxygen content increased.Also the XPS test for the characterization indicate that both catalysts contained Fe²⁺and Fe³⁺at the valence states.?3?In the FeS_x coupled simulated flue gas-air-water micro-nano gas-liquid dispersion system,the removal rate of SO₂ reached 100%,and for the NO catalytic oxidation absorption it was affected by many factors,and the best experimental conditions were:particle size of FeS_x was 300-400 mesh,dosage was 5 g,NaCl concentration was 0.3 g/L,and pH was 5.When the intake amount of SO₂ and NO gas was 200 mL/min,the removal rate of NO reached 95.3%.?4?For the FeS_x coupled air-water micro-nano gas-liquid dispersion system,the removal rate of SO₂ reached 100%.While for the NO catalytic oxidation absorption the main factors that can affect were tested,and the best experimental conditions were:particle size of FeS_x was 300-400 mesh,dosage was 5 g,NaCl concentration was 0.9g/L,and pH was 5.When both SO₂ and NO gas were injected at 200 mL/min,the removal rate of NO reached 89.5%.?5?In the Fe₃O₄ coupled simulated flue gas-air-water micro-nano gas-liquid dispersion system,the removal rate of SO₂ reached 100%.While testing best experimental variables that affecting the catalytic oxidation absorption of NO we found the best conditions were:Fe₃O₄ dosage was 5 g,NaCl concentration was 0.9g/L,pH was 3.When the air intake of SO₂ and NO was 200 mL/min,the removal rate of NO reached 94.7%.