Experimental Study On Carbon Dioxide Conversion By Gliding Arc Discharge

As the main greenhouse gas,CO₂ plays an important role in the global climate change.Therefore,the capture and utilization of CO₂ has become the focus of many researches.In recent years,increasing attention has been paid on atmospheric gliding arc non-thermal plasma for CO₂ conversion and utilization,because it shows the merits of high energy density like thermal plasma and of low energy consumption and good selectivity like non-thermal plasmas,besides,its electron energy level is most suitable for the vibrational activation of CO₂.However,the current researches are not systematic and the conversion of CO₂ is still low.The structure of gliding arc discharge plasma reactor can be greatly optimized.In this regard,this thesis mainly studies the influence of different structure of the gliding arc discharge plasma reactor on CO₂ conversion through the structure optimization of gliding arc reactor and the development of a new type of reactor.Besides,CO₂ is converted by plasma-catalysis with gliding arc discharge reactor first time in this work.In addition,a plasmatron reactor which can form a long plasma jet is further developed and used for the study of CO₂ conversion and the exploration experiments for the co-conversion of CO₂ and biochar.A summary of these results is given as follows:?1?The performance of the reactor is improved by optimizing the design of the gliding arc discharge reactor,and the cubic quartz cover is designed innovatively.The effects of gas flow rate,nozzle structure and quartz cover structure on CO₂ conversion and energy efficiency are studied.The results show that the nozzle diameter of 1.0 mm is better than 1.5 mm for CO₂ conversion;the distance between nozzle and electrode of10 mm shows a better performance,the cubic quartz cover can increase the treated fraction of CO₂ than the traditional cylindrical cover.in addition,it is proved that high temperature can inhibit CO₂ decomposition.?2?A novel magnetically enhanced gliding arc discharge?MEGAD?reactor is developed and investigated for CO₂ conversion.The gliding arc motion and the electrical characteristics?such as discharge waveform,voltage,current,discharge power,etc.?are studied by using high-speed photography and oscilloscope.And systematically studies the effects of magnetic field on arc motion,electrical characteristics and CO₂ decomposition under different flow rates.It is found that there are two modes of arc motion with or without magnetic field under low gas flow,a regular‘ignition–elongation–extinguishment'pattern of a motional gliding arc with a magnetic field and a short-circuiting pattern of a“motionless”gliding arc without a magnetic field.It is proved that the magnetic field can significantly improve the CO₂conversion performance by increasing the plasma area,such as the conversion rate from8.2%to 11.5%.In addition,MEGAD reactor can increase the adaptability of the gas flow range.?3?The work demonstrates the synergistic effect from the combination of a gliding arc discharge plasma with photocatalyst TiO₂ for CO₂ conversion.Particular attention has been paid to the performance of different combination modes of plasma with catalysis,i.e.,in-plasma catalysis and post-plasma catalysis,with emphasis on the analysis of potential mechanisms.A significant synergistic effect of plasma and TiO₂catalyst is clearly evidenced in the in-plasma catalysis mode.In some cases,the CO₂conversion can be improved by 138%?from 4.6%to 10.8%?with the presence of catalyst.The formation of electron-hole pairs on the catalyst surface,which is excited by the high energy electrons in plasmas,should be responsible for the plasma-catalysis synergistic effect.?4?A plasmatron reactor is further developed in order to form a long plasma jet?up to 12cm in length?,which can separate the plasma generation area and the chemical reaction area.In addition,it is the first time to investigate the renewable biochar a reductant for CO₂ reduction.The results show that the addition of biochar significantly increased the CO₂ conversion?up to 21.3%?.Meanwhile,this work demonstrates the feasibility of a simultaneous conversion of CO₂ and biochar in the plasmatron reactor at atmospheric pressure.