| In order to achieve the strategic goal of carbon peaking and carbon neutrality,it is urgent to reduce the use of fossil energy,promote the energy transition and the development and utilization of clean energy.Among them,hydrogen isotope as a raw material for fusion reaction to produce fusion energy is one of the key fields of energy research at present,and the separation and storage of hydrogen isotope is an important step in tail gas treatment and hydrogen isotope recycling after fusion reaction.Due to its good ability to absorb and release hydrogen isotopes,palladium has important application value in the storage,purification and separation of hydrogen isotopes.Therefore,this article took the hydrogen-deuterium exchange process in the palladium bed as the research object to study the coupling mechanism among the diffusion of hydrogen isotopes in the palladium particles,the concentration changes of hydrogen isotope gases in the palladium bed,and the surface adsorption reaction process during the hydrogen-deuterium exchange process.And a multi-scale coupling modle of adsorption,diffusion,and gas flow was established based on COMSOL Multiphysics to analyze the influence of temperature,palladium sphere size and other process conditions on the exchange process.Based on the above-mentioned research,we hope to provide theoretical support for the storage,separation and purification of hydrogen isotopes.The research content and conclusions of this article are as follows:(1)According to the established coupled surface reaction-particle diffusion model,a numerical simulation study of the diffusion and reaction in the hydrogen-deuterium exchange process in the palladium sphere was carried out,and the change rules of hydrogen and deuterium concentration in palladium sphere with time under different temperature,surface activation energy and particle radius were obtained.Numerical simulation results show that within the parameters of the study,when the temperature is 10?,20?and 40?,the corresponding exchange time is 2 s,0.5 s,0.2 s;when the surface activation energy is-22.59k J·(mol H)-1?-26 k J·(mol H)-1,the corresponding exchange time is 0.5 s,1 s;when the palladium sphere radius is 0.5?m,1?m and 5?m,the corresponding exchange time is 0.2 s,0.5 s,10 s.That is,with the increase of temperature,the decrease of surface activation energy and the decrease of the radius,the rate of exchange reaction increases.And the influence of diffusion on the exchange reaction increases with the increase of temperature,the decrease of surface activation energy and the increase of the radius of the palladium sphere.(2)According to the established coupled surface reaction-gas flow model,the numerical simulation of the reaction and gas flow in the hydrogen-deuterium exchange process on the palladium bed was carried out,and the change rules of hydrogen isotope gas concentration with time at different positions of the palladium bed under different temperature,length of palladium bed and inlet pressure were obtained.Numerical simulation results show that during the exchange reaction,a reaction front marked by the peak of HD abundance is formed and moves along the bed,and the exchange reaction is completed when the pressure of the palladium bed reaches equilibrium.Within the parameters of the study,when the temperature is 20??30??40?and 50?,the completion time of exchange reaction is in the range of 55 s to 65 s,and the final deuterium purity in the gas collecting tank is 70.0%,74.0%,78.5%,83.0%;when the length of the palladium bed is 2 cm?2.4 cm?2.6 cm and 2.8 cm,the completion time of exchange reaction is 55 s,60 s,65 s and 80 s,the final deuterium purity in the gas collecting tank is 70.0%?73.2%?88.9%?94.4%;when the pressure at the inlet of the bed is 369 k Pa?379.21 k Pa?387 k Pa and 400 k Pa,the completion time of exchange reaction is 42 s,40 s,38 s,36 s,and the final deuterium purity in the gas collecting tank is 74.9%,70.0%,66.7%and 61.8%.That is,the exchange reaction rate increases with the decrease of the length of the palladium bed and the increase of the inlet pressure,and with the increase of the temperature,the length of the palladium bed and the decrease of the inlet pressure,the purity of deuterium obtained in the gas collecting tank at the outlet of the bed is higher.Finally,the recommended process parameters obtained by simulation calculation under the given conditions in this paper are given as follows:temperature of 40?,palladium bed length of 2.6 cm,and palladium bed inlet pressure at the range of 369 k Pa?379.21 k Pa.(3)Given the same process parameters as the previous hydrogen-deuterium exchange experiments in the coupled surface reaction-gas flow model,the deuterium abundance outflow curve at the outlet of the bed in the hydrogen-deuterium exchange under this condition was obtained and compared with the experimental outflow curve.The results show that the simulation curve is in good agreement with the experimental curve,and the accuracy of the model has been verified. |
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