Oxidation Characteristics Of Carbon Black Particles Based On Thermogravimetric Analyzer

The commercial carbon black（Printex U）and ash particles（ZnO,MgO,Al₂O₃）are used to simulate diesel exhaust particulate and real ash deposited in diesel particulate filter Experiments are carried out on the influence of ash compositions,particle sizes,stacking modes and stacking amount on the oxidation characteristics of carbon black based on the thermogravimetric analyzer.Meanwhile,the comprehensive oxidation index（S）is introduced to perform the oxidation kinetics analysis.The results show that ZnO is able to promote the oxidation of carbon black significantly compared with Al₂O₃ and MgO.With increase of the addition of ZnO,the peak temperature T_P decreases and the comprehensive oxidation index S increases remarkablely.The value of S for the weight ratio of 1:9 of PU/ZnO mixtures reaches（2.15±0.01）*10^-7%²min^-2℃^-3,improved by 120%compared with pure PU.Compared to the large particle size of ZnO（200 nm）,the smaller ZnO（50 nm）enables PU to attain the larger comprehensive oxidation index,which increases by 45%.It is found that the tight contact stratification method is better than other stratification methods such as ash down and ash up,the comprehensive oxidation index of the tight-contact mixture grows by 122%and 138%compared with other methods,respectively,and the peak temperature decreases by 10%and9%,respectively.When the weight ratio of Pu/ZnO is 1:15,the maximum S is（2.21*10±0.10）*10^-7%²min^-2℃^-3,and the lowest peak temperature is（545±1）℃.The comprehensive oxidation index rises by 126%and the peak temperature is 12%lower than pure PU,respectively.It indicates that the existence of ash is conducive to the improvement of the oxidation performance of carbon black.The smaller particle size and tight contact stratification method is beneficial to expand the contact area between ash particles and carbon black particles,so as to make the oxidation more sufficient.However,the oxidation performance of carbon black is hindered by the excessive ash particles.Then,the experiments of the oxidation characteristics of carbon black under different catalyst types（CeO₂,TiO₂）and ash compositions（Al₂O₃,MgO,ZnO）with catalysts are also displayed.Compared with PU/TiO₂ mixtures,PU/CeO₂ mixtures possess the higher comprehensive oxidation index,resulting in prominent oxidation performance enhancement of PU.Because the CeO₂ has the better ability to conserve oxygen.With the increase of CeO₂proportion,the comprehensive oxidation index increases first and then decreases.When the weight ratio between PU and CeO₂ is 1:5,the comprehensive oxidation index increases from（0.98±0.02）*10^-7%²min^-2℃^-3 to（1.58±0.06）*10^-7%²min^-2℃^-3,which grows by 58%compared with pure PU.In the experiments with different ash content,Al₂O₃ and MgO have no positive effect on oxidizing carbon black in the presence of CeO₂ catalyst.While ZnO particles can make carbon black oxidize further,given that the comprehensive oxidation index of PU/CeO₂/ZnO mixture is higher than that of PU/CeO₂/Al₂O₃ and PU/CeO₂/MgO.With increase of the proportion of ZnO,the comprehensive oxidation index tends to grow first and then drop.The most significant impact of potential ash on PU/CeO₂ is observed with 1:5:5 weight ratio of PU/CeO₂/ZnO among soot,catalyst and ash,which has the maximum comprehensive oxidation index（2.41±0.16）*10^-7%²min^-2℃^-3.It shows that CeO₂ and ZnO have the ability to enhance the oxidization performance of carbon black,but excessive addition of catalyst and ash is counterproductive.Finally,the effects of different flow parameters（O₂concentration,inlet flow rate,heating rate）on catalytic oxidation properties of carbon black are conducted.According to the results,the comprehensive oxidation index increases with the increase of oxygen concentration.when oxygen concentration is 15%,the comprehensive oxidation index increases from（0.87±0.02）*10^-7%²min^-2℃^-3 to（1.47±0.07）*10^-7%²min^-2℃^-3,which increase by 69%.It indicates that oxidization behaviour of carbon black occurs more readily due to the more exposed area of the particles in oxygen.With the growth of inlet flow rate,the comprehensive oxidation index increases gradually until the flow rate reaches 100 m L·min^-1,in which the comprehensive oxidation index keeps stable.With the increase of heating rate,the comprehensive oxidation index increases.In general,the inlet flow rate has little effect on the oxidation performance of carbon black,while the increase of heating rate leads to more energy input per unit time,so as to make the particles oxidize rapidly and improve the oxidation speed.The oxidation performance of diesel particles is closely related to the regeneration performance of DPF.A lucubrate investigation on the oxidation performance of diesel particles is able to provide a solid theoretical basis for the improvement of the regeneration for DPF.Based on the experiments,the influence laws of the ash composition,particle size,stacking mode,stacking amount,catalyst type,ash composition in the presence of catalyst and flow parameters on the oxidation characteristics of carbon black particles are investigated by means of the thermogravimetric analyzer,which lays a theoretical foundation for deeper research on the oxidation characteristics of diesel exhaust particles.