Performance And Mechanism Of Fe~ⅡEDTA Denitrification Solution Regeneration By Iron-active Carbon Microelectrolysis

Nitrogen oxides（NO_x）is one of the main atmospheric pollutants,and it’s of great importance to control NO_x emissions effectively.Ferrous complex can absorb NO in flue gas by adding complexing agent,which can combine NO to form soluble complex,and has many advantages such as fast absorption rate,high absorption efficiency and the good compatibility with the existing wet desulphurization system.So it has broad application prospect in the field of flue gas denitration of coal-fired industrial boiler.For this technology,the efficient and selective regeneration of complexing denitration solution（Fe^ⅡEDTA（NO）and Fe^ⅢEDTA）is a key step.This paper adopts the cheap and easy-made iron/active carbon as the reducing agent to conduct experimental research about iron carbon reduction performance and mechanism in complex absorption denitration solution.The main research contents and conclusions are as following.（1）The performance and mechanism of Fe^ⅡEDTA（NO）reduction by Fe/AC were conduct.This article compared the NO removal in the activated carbon,iron powder and iron carbon system,respectively.Factors such as iron-carbon mass ratio,the initial solution pH and the initial concentration of Fe^ⅡEDTA（NO）were selected,and the composition of product under different pH values was analyzed.In addition,the reaction mechanism and kinetics of Fe^ⅡEDTA-NO reduction by iron-carbon were also discussed.Experimental results show that in the same conditions,the removal efficiency of Fe^ⅡEDTA-NO in iron carbon system is much better than that in iron powder system and activated carbon system.As iron-carbon mass ratio was 2,the removal efficiency of Fe^ⅡEDTA-NO is the best.The removal efficiency of Fe^ⅡEDTA-NO increased with pH decreased.The products of NO in Fe^ⅡEDTA-NO are NH₄⁺,N₂ and N₂ O,and pH had certain effects on reducing product selectivity.Furthermore,the reaction of Fe^ⅡEDTA-NO reduction by iron-carbon is first order reaction respect to Fe^ⅡEDTA-NO.（2）The performance of Fe^ⅢEDTA rection by Fe/AC was conduct.This paper compared the Fe^ⅢEDTA reduction by iron-carbon and iron under different stirring speed.The different parameters on Fe^ⅢEDTA reduction were investigated such as the mass ratio of Fe to AC,O₂ concentration,the molar ratio of Fe to Fe^ⅢEDTA,the pH value and the initial concentration of Fe^ⅢEDTA.And the NO removal efficiency was also investigated without and with Fe/AC.The experimental results showed Fe/AC can effectively reduce Fe^ⅢEDTA.The reduction rate of Fe^ⅢEDTA obviously decreased when the concentration of O₂ and pH increased,and when O₂ existed,the surface of Fe/AC was covered with γ-FeOOH;The reduction rate of Fe^ⅢEDTA increased as the stirring speed,the molar ratio of Fe in Fe/AC to Fe^ⅢEDTA and the initial concentration of Fe^ⅢEDTA were raised.Furthermore,the reaction rate constant of Fe^ⅢEDTA reduction by Fe/AC increased with the rise of the initial concentration of Fe^ⅢEDTA.（3）The performance of Fe^ⅡEDTA complexing absorption-Fe/AC reduction dentrification was carried out.The different parameters on regeneration of complexing liquid absorption of NO were investigated such as gaseous flow rate,the oxygen content and the molar ratio of Fe to Fe^ⅡEDTA.And the comparision of denitrification in the activated carbon,iron powder and iron carbon system,respectively.Results showed that the NO removal efficiency increased with the decrease of the content of O₂ and flue gas flow,and the molar ratio of Fe to Fe^ⅡEDTA.