Research On The Efficiency And Mechanism Of Treatment Of Gaseous Pollutants Including H₂S And Toluene By Vacuum Ultraviolet Radiation

Gaseous pollutants have caused serious harm to atmospheric environment and human health.UV photolysis is a relatively new treatment technology for the gaseous pollutants.However,there are several problems in the actual industrial applications: First,the low proportion of short-wave ultraviolet light intensity generated by UV lamps caused low energy efficiency.Second,much higher costs caused by the short life of UV lamp.Third,the need to add auxiliary oxidants and catalysts can easily lead to deactivation of catalyst and complex process.Forth,the by-product of O₃ in tail gas difficult to deal with.Fifth,pollutant degradation is not completely generated intermediate products.Therefore,for these problems,firstly,research and develop long-life new UV lamp which meet the industrial requirements of the high intensity and high proportion of UV₁₈₅ to solve the problems of low energy utilization and short life of UV lamp.Secondly,combined with O₃ produced by O₂ photolysis by UV₁₈₅ to synergistic degrades inorganic and organic gaseous pollutants without adding auxiliary oxidants and catalysts.Thirdly,the combined use of UV photolysis technology and other post-treatment technology will produce synergistic effect,remove the by-products such as O₃ and improve the removal effect of intermediate products of organic gaseous pollutants,achieve the purposes of no O₃ emission and improvement of the mineralization rate of organic gaseous pollutants.The above mentioned three research direction will have great significance in the practical application of UV degradation treatment in gaseous pollutants.This research developed a long-life high frequency electrodeless discharge vacuum ultraviolet?VUV?lamp independently,the UV₁₈₅ proportion is 10% of the total light intensity,the photoelectric conversion efficiency is 30% and theoretical life up to 50 thousand hours.And treatment of gaseous pollutants by high frequency electrodeless discharge VUV lamp,solve the existing problems of the using of conventional UV lamp and microwave electrodeless discharge lamp.Synergistic effect was carried out by the UV light and O₃ produced by UV₁₈₅ on the degradation of H₂ S on behalf of inorganic gaseous pollutants.The degradation rate of H₂ S decreased with increasing of initial concentration of H₂ S and increased with increasing of humidity and oxygen content.The UV-photolysis and ozone oxidation alone have limited capacity to treat H₂ S,and the synergistic degradation rate is 30%-66% higher than that of the photolysis and ozone oxidation alone,and the initial concentration of H₂ S is higher,the more obvious synergies.The reaction kinetics and synergetic mechanism by mathematical model were studied.And UV reactor model for degradation of H₂ S and flow field and radiation field of photochemical reactor were established.And the mathematical simulation and kinetic simulation of UV-photolysis and ozone oxidation alone were carried out.The simulated values of degradation rate are basically the same as the experimental values.The photolysis products are mainly H₂ and S,ozone oxidation products are mainly SO₂ and SO₃.The results of the simulation of the influence on degradation rate by the initial concentration of H₂ S,the inlet air flow and relative humidity is consistent with the trend of the experimental value,and the numerical deviation is small,thus proving the correctness and validity of the model.Degrading toluene on behalf of organic gaseous pollutants by synergy effect which adding the ozone catalytic oxidation process after the photolysis process as post treatment process.Adding Mn O₂/activated carbon as catalyst in the ozone catalytic oxidation process,it can not only solve the problem of residual ozone in the treatment of indoor organic gaseous pollutants by the air purifier which UV photolysis technology as the core,but also improve the removal effect of the degradation of organic gaseous pollutants,achieving the purpose of non-ozone emissions and improving the mineralization rate of organic gaseous pollutants.When degradation of toluene,the photodegradation reactor and the ozone catalytic oxidation reactor were optimized and designed,the influence factors of the degradation of toluene were studied,including the initial concentration of toluene,relative humidity and inlet air flow,the influence factors of the degradation of toluene by ozone catalytic oxidation alone were analyzed,including the initial toluene concentration,inlet flow rate and O₃ concentration.Under the synergistic effect of photolysis and ozone catalytic oxidation process,the mineralization rate of toluene is higher than the sum of the individual UV-photolysis and the ozone oxidation alone.The synergistic effect is due to the enhancement of the oxidation ability of ·OH and ·O by the presence of 185 nm vacuum ultraviolet light,which acidification and opening the benzene ring at the same time after generating benzyl alcohol and benzaldehyde,generating small molecules intermediate products such as formic acid and acetic acid directly.Compared with toluene,the intermediates of benzyl alcohol,benzaldehyde,formic acid and acetic acid are more likely to be completely mineralized by the O₃ catalytic oxidation system.