Research On Methane Conversion Through Non-equilibrium Plasma

Methane is a principal component of natural gas.With the lack of crude oil resources in the world,the development of methane utilization as the feedstock, instead of crude oil,for the production of chemical has been extensively studied.The application of plasma technology is continuously growing in chemistry,metallurgy, microelectronics,and environmental protection.Generally,two very different kinds of plasma are used for research and industrial applications:hot quasi-equilibrium plasmas and cold non-equilibrium plasmas.One of the challengens of modern plasma chemistry is to unite the advances of these two very different plasma systems. Most of the large-scale plasma chemical applications require high power and high pressure for high reactor productivity.It is also important to have a high degree of non-equilibrium with high electron temperature and density to support selective chemical processes.Therefore,it is necessary to have a powerful dscharge that generates non-equilibrium plasma for chemical applications with both high efficiency and selectivity.In this study,the non-thermal equilibrium arc discharge and DBD experiments were investigated through the measurements.The methane coupling reaction and carbon dioxide reforming methane reaction were performed.The results of the methane conversion in those two plasmas showed that non-thermal equilibrium plasma from the gliding arc and DBD could convert methane to goal product efficiently.And promising composition of C₂ hydrocarbon / syngas outputs were obtained.Here lists the main work:The new type of non-thermal equilibrium arc discharges driven by magnetism experimental setup(including high voltage power supply,electromagnetic filed generator and other correlated parts) was established.(Magnetic field intensity B≈0～1.4T,alterable power supply voltage:2000～7500V).The high speed CCD and Photomultiplier Tube(PMT) were used to measure the velocity and diameter of arc and to observe the arc motion.Simultaneously the key parameter,electric field intensity was measured directly.And then we deduced the current intensity,and analyzed the phenomena of non-circular-symmetrical arc section.According to the electric field intensity,arc current,combining bidimensional heat transfer model,the neutral particle temprature,arc section area and non-equilibrium degree of plasma were calculated and compared with our work. And the arc in our work has higher velocity,electric field density and non-equilibrium degree.The methane conversion to acetylene in magnetic driving gliding arc discharge reactor was performed.Gas chromatogram was used to analyze the product.The results showed that the flux of material gas affected the conversion rate and selectivity of the material.Increased SE(specific energy) and magnetism intensity could enhance the selectivity and yield of the products.DBD discharge was performed in the co-axial quartz cube by using the high frequency power supply.Different dielectrics(Al₂O₃ grains and ceramic fibers) were filled in the discharge space and the experiments were compared.The current, voltage,electricity and discharge power were measured and calculated along with the changed experimental condition.The results indicated that the DBD produced by our discharge device was corona induced DBD.The carbon dioxide reforming methane reaction was performed in the DBD reactor.The results were analyzed.At last the reaction process of methane and carbon dioxide coreaction was investigated.