| Nitrogen tetroxide(N2O4)has been widely used in the aerospace field because of its strong oxidizing property and good combustion-supporting ability.The launch site w ill inevitably leak during the daily use of nitrous oxide,producing a large amount of highly toxic reddish-brown gas(mainly nitrogen dioxide NO2).If the NO2 waste gas leaked from the space launch site is discharged directly without treatment,there will be a significant threat to the ecological environment around the launch site and to the health of those on site.The NO2 waste gas chemical absorption treatment devices currently used in my country’s space launch sites generally have problems such as low treatment efficiency,large equipment investment,and poor mobility.Supergravity equipment has the advantages of high mass transfer efficiency,strong mobility,and easy operation and maintenance.Therefore,this subject combines high-gravity equipment with chemical absorption to enhance the liquid propellant NO2 exhaust gas removal process.In this paper,a mixed solution of Na2S/NaOH and H2O2/NaOH is selected as the absorbent,and the high-concentration NO2 cylinder gas purchased in the laboratory is used to simulate the propellant NO2 waste gas,and the NO2 removal experiment is carried out in a rotating packed bed(RPB),Explore the influence of key process conditions on NO2 removal efficiency and gas-phase mass transfer coefficient in the removal process,and conduct liquid phase analysis of its absorption products to verify the reaction mechanism of the experimental system.The main research results are as follows:(1)When using Na2S/NaOH mixed solution to remove NO2 waste gas,the results of the study showed that as the RPB speed,absorbent concentration,and absorbent pH increased,the NO2 removal efficiency and mass transfer coefficient increase correspondingly.The change of absorbent temperature has little effect on NO2 removal rate and mass transfer coefficient.When the gasliquid ratio and gas flux increase,the NO2 removal rate decreases obviously,but the gas mass transfer coefficient increases first and then decreases,showing the best mass transfer performance at G/L=200 and G=1.5 m3/h,respectively.In addition,after liquid phase analysis of the absorption products of the system,it was found that most of the absorbed NO2 gas was reduced to N2 and then discharged from the system,while the rest of the absorbed NO2 gas was converted to NO2-and NO3-in the liquid phase,so that a certain amount of nitrite and nitrate wastewater would be generated in the absorption process.(2)When H2O2/NaOH mixed solution was used to remove NO2 from the exhaust gas,the results showed that the NO2 removal rate and gas-mass transfer coefficient first increased and then remained at a fixed level with the increase of RPB rotating speed,absorbent concentration and absorbent pH.When the gas liquid ratio and gas flux increase,the NO2 removal rate decreases significantly,while the gas mass transfer coefficient increases accordingly.In addition,no NO2-was detected in the liquid phase ionic analysis of the absorbed products of this system,indicating that the strong oxidation property of H2O2/NaOH can oxidize all the absorbed NO2 gas into NO3-in the liquid phase,avoiding the generation of nitrite wastewater and thus reducing the cost of subsequent wastewater treatment. |
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