Research On The Technology And Key Indicators Of Auto Exhaust Gas Self Collection And Filtration

Air governance has always been a key and difficult aspect of the environmental governance system.Automobile exhaust is a major source of air pollution,and the2021 China Mobile Source Environmental Management Annual Report showed that the four main detection indicators accounted for over 90%of the total pollution in the country.Currently,the treatment method for photocatalytic degradation of automotive exhaust gas is mainly surface coating.The photocatalyst is made into a coating and applied to the surface of the road or transportation infrastructure to form a passive method for degradation of automotive exhaust gas.Although the degradation of exhaust gas has achieved initial results,most of the exhaust pollutants are suspended in the air,unable to effectively contact the photocatalytic coating,and the effect is still not very ideal.Currently,most of the exhaust gas degradation efficiency testing tests focus on static gas state testing,that is,introducing quantitative automotive exhaust gas in a closed environment,using nano-TiO₂as a photocatalyst to conduct static degradation research.However,the actual road scene environment is complex,and the photocatalytic degradation of exhaust gas is mostly in open spaces,with relative air circulation.Static tests limit the flow of automotive exhaust gas,and the tests cannot simulate the natural factors in real scenes.A vehicle exhaust gas filtration technology needs to be improved,and an air filtration application device capable of actively absorbing exhaust gas and degrading exhaust gas pollutants within itself needs to be developed and designed.In addition,this paper conducts research on the corresponding theoretical research deficiencies of self collecting exhaust gas degradation rate.（1）According to the characteristics of road use,this paper proposes a vehicle exhaust gas filtration technology,and designs a vehicle exhaust gas filtration device with self collection function for road use.In response to the current passive degradation mode of road coated coatings,an exhaust system is installed in this device,which relies on active air exchange to collect air inside the device and cooperate with nano TiO₂photocatalysts to degrade exhaust pollutants in the air and filter the air.Use the COMSOL Multiphysics platform to simulate and explore the stratification law of internal air velocity.Use Matlab to fit the inlet flow rate and internal maximum flow rate of the device,verify the relationship through SPSS analysis,and determine a one-dimensional quadratic relationship,where x represents the inlet flow rate,y represents the maximum flow rate,and y=-3.77x ²+8.52x+0.057.（2）In order to determine the specific impact indicators of the self collecting filtration and digestion device on the degradation rate of exhaust gas,an indoor test model was designed and a dynamic degradation efficiency detection mode was established.Using flowing automotive exhaust as the test source,instead of static degradation,the flow of automotive exhaust throughout the test process was maintained.Concentration detection devices were installed at both ends of the reaction chamber,using NO as the indicator gas.Based on the average value of light intensity within a year in major regions in China,the test light intensity was determined to be 20.03W/m².The dynamic degradation test was conducted using anatase nano titanium dioxide with high photocatalytic efficiency at this stage as a catalyst.（3）Establish evaluation indicators for dynamic degradation tests.The dynamic degradation test is different from the static test,and using the original static test evaluation indicators cannot accurately evaluate the degradation effect.In response to the above issues,this test was optimized based on the original indicators,adopting a segmented approach,dividing the overall test time into equal intervals,with each interval being considered as a unit time and serving as a benchmark for the evaluation system.The evaluation indicators were optimized,and the dispersion of degradation efficiency per unit time was verified using standard deviation indicators.This method can effectively avoid errors and accurately reflect the changes in tail gas degradation rate.（4）In this experiment,two test variables,namely,the flow rate of exhaust gas and the concentration of photocatalyst,were controlled simultaneously.Through analyzing the test results of different flow rates of exhaust gas,and combining the impact of the concentration of nano-TiO₂photocatalyst on the degradation rate,the role of nano-TiO₂photocatalyst on the degradation rate was jointly explored.It was found that the degradation efficiency of automotive exhaust gas is the most ideal when the coating concentration of nano TiO₂photocatalyst is 40g/m²and the exhaust gas flow rate is 2.5m/s.It provides theoretical basis and data support for the application of automotive exhaust gas self collection and filtration devices and research on self collection and filtration technology,and clarifies the key indicators of automotive exhaust gas self collection and filtration technology.