Performance And Mechanism Of Simultaneous Purification Of NOx And VOCs By Wet Oxidation Method

NO_xand VOCs are important precursors for the formation of haze and ozone.Biomass boiler flue gas is an important source of NO_xand VOCs.The absorption oxidation technology has the advantages of high purification rate and low secondary pollution,in which,as a clean oxidizer,H₂O₂has strong oxidation ability and low cost.In this study,the purification performances of H₂O₂solution and H₂O₂activated Na HCO₃solution system for single NO gas and single acetone gas were investigated,respectively.The response surface method was used to verify and optimize the process parameters determined under single factor conditions.By analyzing gas-liquid two-phase products and other means,the absorption and oxidization reaction mechanisms of liquid-phase H₂O₂for NO and acetone gas were respectively investigated.On this basis,the simultaneous purification performance and mechanism of NO/acetone by liquid-phase H₂O₂were systematically studied,and the thermodynamic process was analyzed.The results are as follows.1)Purification performance and mechanism of liquid-phase H₂O₂for NO gas:when the concentration of H₂O₂solution was 0.7%,p H was 8,solution temperature was 50℃,and gas residence time was 160 s,the highest removal rate of NO was 48.2%.The addition of Na HCO₃promoted the production of·O₂^-and the removal rate of NO increased by 11%.The oxidation of NO by H₂O₂was the combined action of·OH and·O₂^-,in which·O₂^-played the main role.Based on the product analysis results,the reaction mechanism model for H₂O₂oxidation of NO was proposed.2)Purification performance and mechanism of liquid-phase H₂O₂for acetone gas:under acidic conditions,when the concentration of H₂O₂was 0.7%,p H was 4,temperature was 20℃,and gas residence time was 160 s,the highest removal rate of acetone was94.7%.Under alkaline conditions,when p H was 8,the highest removal rate of acetone was 86.2%,when activator Na HCO₃was added,the removal rate of acetone only increased by 2%.Under acidic conditions,the main free radical of acetone oxidation by H₂O₂was·OH.Acetone and acetic acid were detected in liquid-phase products.The mechanism model for H₂O₂oxidation of acetone gas was proposed.3)Simultaneous purification performance and mechanism of liquid-phase H₂O₂for NO/acetone mixture gas:under the optimal conditions（the concentration of H₂O₂was0.7%,temperature was 50℃,p H=8,gas residence time was 160 s）,compared with a single component of NO,the removal rate of NO in the gas mixture was increased by8%-11%,while the removal rate of acetone in the gas mixture was decreased by 2%-8%compared with that of a single component of acetone.In the H₂O₂activated Na HCO₃solution system,the removal rate of NO in the gas mixture increased to 67.4%,however the removal rate of acetone only increased by 3%.The results showed that acetone had a synergistic effect on the removal of NO,and the mechanism model of the synergistic oxidation process was proposed.4)Thermodynamic analysis showed that the simultaneous removal of NO and acetone by H₂O₂was an exothermic reaction,and the oxidation removal reaction is feasible,and the limit of reaction was very deep.Compared with NO,acetone was more easily and thoroughly oxidized by H₂O₂.