Effect Of Ozone Concentration In NTP On DPF Regeneration And Particulate Matter Oxidation Removal

Diesel particulate matter（PM）is one of the main air pollutants,and excessive emissions can seriously affect traffic and travel,and even damage human health.Using non-thermal plasma（NTP）technology can oxidize and remove PM at a low temperature（<200℃）,which has the advantages of clean,high efficiency and no secondary pollution.NTP has become a hot research topic in diesel exhaust treatment.Ozone plays an important role in the oxidation and removal of PM in NTP.Therefore,it is important to study the kinetic parameters of the thermal decomposition reaction of ozone itself.To find the self-consistent temperature of the reaction can inhibit the thermal decomposition of ozone and promote the oxidation of PM removal by ozone,which is important to control the emission of diesel exhaust pollutants and protect the environment.The effect of different ambient temperature control strategies on the rate,internal temperature and product concentration of NTP regenerated DPF was further investigated based on the study of ozone properties.The discharge voltage and frequency of the NTP generator were varied to oxidize PM samples in a temperature-controlled reaction chamber with different ozone concentrations of NTP active gas within a certain reaction time.The reaction was carried out using fourier transform infrared spectroscopy（FT-IR）,gas chromatography-mass spectrometry（GC-MS）and thermogravimetric analysis（TGA）.The effect of ozone concentration on the oxidative removal of PM surface functional groups and soluble organic fraction（SOF）was investigated by means of TGA.The evolution of ozone concentration on the oxidative removal of PM by NTP was investigated in depth.The work and main results of the thesis are as follows.（1）An online test system was built to detect the time variation of ozone concentration at different temperatures,and the thermal decomposition of ozone was analyzed.The activation energy of ozone thermal decomposition reaction,the parameters of reaction kinetic equation and the relationship between the concentration and time variation of ozone decomposition were investigated.The reaction rate and kinetic equation of ozone decomposition were derived from the ozone thermal decomposition equation and Arrhenius equation.It is shown that the activation energy of ozone thermal decomposition reaction Ea=2.80755104 J/mol,the reaction rate constant is k=190.76×e^{（-2.80755×104）/RT},and the relationship of ozone concentration with temperature and time is:c=(1-(190.76×e^{（-2.80755×104）/RT})·t)·c₀.（2）By changing the environmental temperature control strategy of ozone regenerated DPF,the changes of regeneration time,product concentration and internal temperature of ozone regenerated DPF under constant temperature and non constant temperature conditions were explored.Combined with the thermal decomposition law of ozone,the macro influence of environmental temperature on ozone regenerated DPF was analyzed,and a better temperature control strategy for ozone oxidation to remove PM was needed.The results show that the peak values ofΔT at all internal measuring points during the regeneration of DPF with ozone under constant temperature are lower than those under constant temperature,and the decomposition loss of ozone under non constant temperature is lower than that under constant temperature.The strategy of regenerating DPF with ozone can be selected as follows:maintain the environment of80℃～100℃at the initial stage of regeneration to ensure the rapid start of reaction;when the internal temperature of DPF exceeds 130℃,start to cool the DPF to speed up the heat emission and ensure the efficient utilization of ozone.（3）In order to study the effect of ozone concentration on the removal of PM by NTP,a self-made NTP generator was used to produce NTP active gas with different ozone concentration by changing the discharge conditions with O₂ as the gas source.FTIR,TGA and GC-MS were used to analyze the PM samples before and after NTP reaction.The removal and oxidation effects of volatile fraction（VF）,soot and SOF of PM were studied,and the oxidation mechanism of different concentration of ozone NTP gas on PM was explored.The results show that C=C in PM is broken and O atom is inserted into the carbon chain to form C-OH group.With the increase of ozone concentration in NTP,C-OH group was gradually oxidized to C=O group.The removal efficiency of NTP on PM is obvious.More than 38%of PM can be removed by oxidation at low ozone concentration（20 g/m³）,and with the increase of concentration,the removal rate also increases,reaching 51.7%（50 g/m³）.With the increase of ozone concentration in NTP gas,the alkane content of sof in PM gradually decreases,and the content of components with oxygen-containing functional groups increases.The number of oxygen atoms in the carbon chain also increases with the increase of ozone concentration.After NTP,the VF volatilization onset temperature,VF maximum weight loss rate temperature,and soot maximum weight loss rate temperature of PM samples all decrease.VF volatility and soot oxidation activity are all enhanced.The increase of ozone concentration enhanced the oxidation effect of NTP on different components in PM.The law of ozone decomposition was explored,and the temperature control strategy of NTP regeneration DPF was designed and optimized according to the change law of ozone concentration in the thermal environment.On this basis,the ozone utilization rate in the process of NTP regeneration of DPF was improved,and the PM in DPF was promoted.The removal efficiency.In-depth exploration of the changes in the composition of VF and SOF during the oxidation and removal of PM with different concentrations of ozone in NTP,the study found that high concentrations of ozone can remove more PM,and break the longer components of the molecular chain in PM,type O atom,forming an oxidation product with a shorter molecular chain.These oxygen-containing reaction products have high volatility and oxidation activity.This study explained the mechanism of ozone concentration on the promotion of PM removal by NTP oxidation and revealed the evolution process of PM removal by NTP oxidation.