Dielectric Barrier Discharge Reactor Optimization And Enhanced Hydrogen Isotope Exchange Application Study

The separation of hydrogen,deuterium and tritium by cryogenic distillation technology is mainly based on the concentration of hydrogen isotopes in different regions within the reaction column with small differences in their physical or chemical properties.During the hydrogen isotope exchange reaction,without external electromagnetic excitation or chemical catalysis,the reaction kinetics of the exchange reaction would take tens or even hundreds of years to reach reaction equilibrium.Currently,the performance of catalysts,the core materials required for hydrogen isotope exchange in thermocatalytic processes,determines the catalytic exchange efficiency.Although some noble metal-based catalysts exhibit high catalytic activity and can enhance the catalytic exchange efficiency,the increase in catalytic activity brings about problems such as instability of surface active metal atoms and complication of preparation process,which not only reduces the catalyst lifetime but also increases the difficulty of mass production and its expensive cost is not conducive to commercial applications.Therefore,there is an urgent need to introduce new technological approaches to solve the current bottleneck problems.Low-temperature plasma catalysis is currently receiving a lot of attention worldwide.In low-temperature plasmas,electric field-induced ionization dominates the thermal process and can generate highly reactive particles and free radicals that can break most chemical bonds,allowing thermodynamically unfavorable reactions to occur at low temperatures.Dielectric barrier discharge(DBD),as one of the main ways to generate low-temperature plasma in industry,generates high density of electrons during the discharge process that can easily break molecular chemical bonds.However,usually DBD discharge is mainly in filamentary discharge mode,and the spatial non-uniformity of filamentary discharge inhibits the practical application effect of DBD.In this paper,we first analyze the electrical characteristics of DBD to study the influence of external parameters on its discharge performance,and improve the uniform stability of the discharge by optimizing the reactor,and then reduce the energy loss.On this basis,DBD is used to generate low-temperature plasma for experimental study of hydrogen isotope exchange and to compare and analyze with the conventional thermal catalytic conversion process.The main research of this paper is as follows:(1)An experimental system of coaxial dielectric blocking discharge was built.The influence of electrode material on the discharge characteristics of DBD is investigated,and it is pointed out that the screen electrode can influence the electric field to produce local enhancement effect,and the discharge spot depends on the aperture of the screen electrode,which is formed at the grid node of the screen electrode,and the aperture diameter of the screen electrode can significantly influence the discharge characteristics of DBD,and the reduction of its aperture diameter makes the electric field distribution relatively uniform.In addition,it is pointed out that the foil electrode can reduce the abnormal air breakdown outside the reactor tube and the gap between the electrode and dielectric and thus improve the energy efficiency,and there are various forms of energy conversion in the discharge process of DBD reactor,resulting in different foil electrode materials to make the electron emission requires different energy.(2)The discharge characteristics of a multi-stage DBD reactor were investigated,and it was pointed out that changes in electrode structure can cause changes in the electric and flow fields,and the equivalent capacitance and transferred charge during the discharge of a multistage DBD reactor increase approximately linearly with the increase in the number of discharge stages.In addition,the variation of discharge characteristics was explored by using different internal and external electrodes in the DBD system.The use of copper foil as a highvoltage electrode expands the effectiveness of the discharge region compared to a mesh electrode,while the single-layer dielectric DBD discharge favors secondary electron emission,causing enhanced discharge intensity.Both effects contribute to the uniform stability and energy efficiency of the plasma discharge.(3)The effect of electrode structure on the electric field distribution in the DBD reactor was investigated using COMSOL multi-physics field simulation software.It is pointed out that the average electric field is the initial factor to determine the discharge ignition,but too high average electric field will lead to channel separation or even flow injection,and the differential electric field generated by multi-stage structure is beneficial to the diffusion of discharge channels,which in turn reduces the discharge channel separation or even flow injection.(4)Hydrogen isotope exchange experiments were carried out using conventional thermal catalysis,and the catalytic exchange reaction was able to reach reaction equilibrium relatively quickly at room temperature,but the catalyst activity was affected at low temperature,which made it difficult to break the intermolecular potential barriers and thus affected the catalytic reaction.In contrast,the low-temperature plasma-catalyzed reaction reaches reaction equilibrium almost instantaneously under ambient conditions,and the low-temperature plasma technology achieves efficient catalytic conversion under low-temperature conditions.