Study On Removal Of NO_x From Flue Gas By Indirect Electrochemical Oxidation

As flue gas nitrogen oxide（NO_x）emission standards become increasingly strict,economical and efficient nitrogen oxide control technologies are urgently needed in the chemical industry,steel and shipping industries.At present,the flue gas denitrification technology used in industrial applications is often difficult to balance economy,high efficiency and environmental protection.In recent years,indirect electrochemical oxidation denitrification technology by seawater electrolysis for preparing available chlorine had emerged.The low operating cost made it have a good application prospect,but it still has problems such as low NO_x removal efficiency and low oxidant utilization rate.To solve the above problems,this article systematically explored the indirect oxidation denitrification process of Na Cl O produced by anode cyclic electrolysis producing Na Cl O,and constructed a cathode and anode paired electrolysis synergistic oxidation denitrification process,that is,through paired electrolysis,the cathode and anode can simultaneously generate H₂O₂and available chlorine to NO_x.Synergistic oxidation removal.On this basis,the resource utilization process of denitrification waste liquid was explored.First,the electrolysis process and denitrification process of the anode cyclic electrolysis indirect oxidation process were optimized,so that the system reached a NO_x removal efficiency of 76.8%after 30 min of pre-electrolysis;the continuous denitrification performance of the system was studied,and the results showed that continuous electrolysis at an anode current density of 2 m A/cm² can maintain a NO_x removal efficiency of more than 76.4%within 60 min;the constructed acidic oxidation-alkaline absorption process increases the system’s NO_x removal efficiency to 82.2%.Secondly,based on the optimization of the cyclic electrolysis process,the anode and cathode paired electrolysis synergistic oxidation denitrification process was proposed.Paired electrolysis produces two oxidants at the cathode and anode at the same time,and its current efficiency can reach 148.3%.The two oxidants can synergistically oxidize NO_x,and obtain a higher NO_x removal efficiency than single anode electrolysis with lower energy consumption;The synergistic oxidation mechanism of NO_x originates from:NO is first oxidized to NO2 by HCl O in the anode absorption solution,the remaining part of NO and NO2 is oxidized by the H₂O₂ in the cathodic absorption solution,and part of the NO and NO2 is absorbed by the OH^-in the cathodic absorption solution The optimized paired electrolysis cooperative oxidation process was electrolysis for 60 min under the conditions of cathode current density of 1.5m A/cm²,cathode and anode area ratio of 1.5:1,anode Na Cl concentration of 10wt.%,and cathode air flow of 1 L/min.The NO concentration is 1000 mg/m3 and the flue gas with a flow rate of 0.5 L/min achieves a NO_x removal efficiency of 95.6%.Finally,in view of the resource utilization of cathode denitrification waste liquid produced by synergistic oxidation denitrification,a two-stage evaporation crystallization process was designed based on the principle of phase separation.The first-stage evaporation capacity was75 g,the first-stage crystallization temperature was 1°C,and the second-stage evaporation The amount is 6.5 g and the secondary crystallization temperature is 25°C.The purity of the Na NO3product is 98.16%,which meets the national standard GB/T4553-2002 industrial sodium nitrate qualified product.