Construction Of Photochemical Spray System In Pilot Scale And Study On Simultaneous Desulfurization And Denitrification

NO and SO₂ are the major pollutants emitted from coal-fired boiler flue gas,which have caused environmental pollution and acid rain,posing a great threat to ecosystems and human health.At present,the combination of wet flue gas desulphurization and selective catalytic denitrification have been widely used to control emissions at home and abroad.However,this type of grading treatment has disadvantages of complex systems,large land occupation,high investment and operating costs.Duing to technical and economic problems,it is difficult for small and medium-sized boilers to adopt a adesulfurization and denitrification device as large-scale boiler.The integrated desulfurization and denitrification technology can overcome these shortcomings,becoming one of the hotspots in the field of current combustion pollution control.In this paper,a pilot-scale photochemical spray tower is designed and built on basis of a lab-scale UV-bubble column reactor.In the spray tower,the main influencing factors and reaction mechanism on integrated desulfurization and denitrification by VUV?vacuum ultraviolet?/H₂O₂ advanced oxidation process are studied.On this basis,the additives of NO and SO₂ absorption are screened.The main contents and results are as follows:The main influencing factors of NO removal process by VUV/H₂O₂ advanced oxidation process are studied.The results show that Initial NO concentration and flue gas flow rate are two factors that are detrimental to NO removal,NO removal efficiency will have a significant reduction with the increase of initial NO concentration and flue gas flow rate.Solution temperature has a slight influence in NO removal,which will cause a slight decrease of NO removal efficiency by increasing solution temperature.Increasing UV radiation light intensity and H₂O₂ concentration is beneficial to removal NO,and the NO removal efficiency will increase rapidly at first and then gradually become stable.With the increase of liquid-gas ratio,the NO removal efficiency increasesfirstly and then decreases,there is an optimal liquid-gas ratio.The main influencing factors of NO and SO₂ removal process by VUV/H₂O₂advanced oxidation process are studiedand the removal mechanism is analyzed.The results show that SO₂ can be completely removed under different influencing factors.with the increase of flue gas flow rate and initial NO concentration,the removal efficiency of NO will decrease significantly.The removal efficiency of NO will increase rapidly at first and then gradually become stable with the increase of UV radiation intensity and H₂O₂ concentration.With the increase of liquid-gas ratio,the NO removal efficiency increases firstly and then decreases.The presence of SO₂ has an effect on NO removal,the removal efficiency of NO will slightly decrease with the increase of SO₂ concentration.Sulfuric acid and nitric acid as reaction products,have an effect on the removal of NO.They have a slight inhibitory effect on the NO removal process in a low concentration,while having a certain strengthening effect at a high concentration.The VUV/H₂O₂ advanced oxidation process achieves integrated removal by the oxidative removal of H₂O₂ solution itself and OH radical which generated by ultraviolet light irradiation and the effect of the reaction products on simultaneous removal.The effects of three additives including calcium oxide,urea and ammonium persulfate on simultaneous removal of NO and SO₂ by VUV/H₂O₂ advanced oxidation process were investigated.The results show that SO₂ can be completely removed under different additives.And with the increase of additive concentration,it spends less time to reach equilibrium.The addition of calcium oxide,urea,and ammonium persulfate all enhance the NO removal efficiency.With increase of calcium oxide concentration and urea concentration,NO removal efficiency will increase firstly and then stay stable.With the increase of ammonium persulfate,NO removal efficiency will increase rapidly at first and then grow slowly.The time for NO to reach equilibrium will be shorter while increasing the concentration of the three additives.By comparing and analyzing the three additives,the best additive is ammonium persulfate.