Experimental Study On Simultaneous Desulfurization And Denitrification By NO Oxidation Combining Liquid Phase Absorption

SO2 and NOx produced by coal combustion are one of the most important sources of air pollution in China.As the traditional and single-function flue gas pollution control method is applied,the flue gas pollution control chain is becoming longer and longer,leading to complex process system,large area,high investment and high operation cost.So the new integration technology of desulfurization and denitrification is still the research hotspot in the field of coal-fired flue gas control.The wet integration technology of desulfurization and denitrification is one of the most promising technology solutions.In this paper,potassium permanganate and plasma were used to realize the oxidation of NO respectively.And the reactive process and mechanism of simultaneous desulfurization and denitrification by NO oxidation combining NaOH liquid phase absorption were explored,which provided the theoretical basis and technical support for the application of the integration removal technology of multiple pollutants in flue gas.The content of this paper was divided into three parts:(1)Simultaneous liquid phase absorption of SO2 and NO2 by NaOH solution.The reaction process and interaction mechanism of SO2 and NO2 in the absorption process were focused;(2)Simultaneous removal of SO2 and NO by KMnO4 oxidation combined with NaOH liquid phase absorption,the key influencing factors of simultaneous desulfurization and denitrification and the interaction mechanism of NO and SO2 absorption were studied.(3)Simultaneous desulfurization and denitration by NaOH liquid phase absorption coupled with plasma oxidation.The process of simultaneous desulfurization and denitration by corona discharge coupled with wet absorption was studied emphatically.The reaction mechanism was analyzed and the synergistic effect of corona discharge coupled with wet absorption was explored.The main results were as follows:The NO absorption effect by NaOH alone was very poor,and the removal rate of NO was only about 5%.The NO2 absorption effect by NaOH alone was better than that of NO,and the removal rate of NO2 was more than 30%.When NaOH was used to absorb SO2 and NO2 simultaneously,the reaction products of Na2SO3 and NaHSO3 can promoted the absorption of NO2.In this case,the removal efficiency of SO2 reached 100%and NO2 removal rate was about 60%.The increase of NO2 initial concentration had little effect on the desulfurization,while the removal rate of NO2 increased with the initial concentration of SO2.When SO2 concentration rose from 400 ppm to 1000 ppm,the removal rate of NO2 increased from 28%to 60%.(2)In the process of simultaneous desulfurization and denitrification by KMnO4/NaOH,the KMnO4 concentration had a great influence on the removal of NOx while the effect on the removal of SO2 was less.The moderate amount of SO2 concentration could promote the removal of NOx,and thus the SO2 played a synergistic role.However,when the SO2 concentration was too high,the absorption of SO2 and NO2 had a competitive reaction,and increasing the SO2 concentration would decrease the NOx removal rate.For SO2,its removal mainly depended on the neutralization reaction of NaOH,increasing the initial concentration of NO would not have an obvious impact on the removal of SO2.But the increase of the initial concentration of NO could decrease the removal rate of NOx gradually.The effect of increasing flue gas flow rate on SO2 removal was small,but the removal rate of NOx would be reduced significantly,and the NOx removal rate would decrease from 60%to 35%.Increasing oxygen content,the removal of SO2 was not affected,but it contributed to the oxidation of NO and the NOx removal rate increased slightly.The increase of flue gas temperature was not conducive to the removal of SO2 and NOx.And the temperature had a bigger effect on the solubility of S02.Meanwhile,the absorption of SO2 was exothermic reaction,the temperature increase was unfavorable to the reaction;The increase of dust concentration was unhelpful to the absorption of SO2 NOx,especially to the SO2,which was mainly because of that the soot hindered the contact of SO2 and desulfurizer to some extent.(3)In the process of simultaneous desulfurization and denitration by wet absorption coupled with corona discharge,the addition of the absorbent increased the energy injection level of corona discharge.At the discharge voltage of 15 kV,the absorbent of 0.2 L/min could increase the input energy to 4.8 W.The removal rate of NOx in single corona discharge was 14.3%while the removal rate of NOx in the individual absorption was 7.7%.The removal rate of NOx in the corona coupling wet absorption process reached 58.2%.The transformation of NOx in the process of corona coupled wet absorption mainly relied on the synergy of corona discharge and wet absorption.The increase of liquid-gas ratio would significantly improve the removal rate of S02,but it had less effect on NOx removal.NOx removal was mainly affected by corona discharge,and the removal rate of NOx increased obviously with the increase of discharge voltage.This indicates that the removal of NOx was the result of the combination of low temperature plasma oxidation and chemical absorption,and the removal of SO2 was more dependent on chemical absorption.The NaOH concentration had little effect on the removal of S02.However,for the removal of NOx,the removal rate of NOx under 5kV voltage was not obvious.But at high discharge voltage,because NO was effectively oxidized to N02 and then N02 reacted with NaOH and Na2SO3,the NOx removal rate significantly affected by the change of NaOH concentration.