Study On Separation Of Hydrogen Isotopes By Low-temperature Preparative Chromatography With Gradient Heating Method

The separation of large-scale hydrogen isotopes is a key technology to be solved in the process of nuclear fusion energy development and utilization.So far,there are few hydrogen isotope separation techniques suitable for industrial scale applications,and cryogenic preparative chromatographic separation technology has advantages in terms of simple equipment,reliable operation,large separation factor,high product purity,and low retention of tritium in fusion reactor fuels.In this paper,some shortages in the separation process of low temperature preparative chromatography are analyzed theoretically,such as the mass transfer heat transfer process and process conditions in the chromatographic column.The gradient temperature field is mainly used to promote the preparation of chromatographic separation.The mechanism of hydrogen isotope separation is explored and the adsorption-desorption experimentsare carried out.The main research contents and results are as follows:(1)Theoretical analysis of the mechanism and influence factors of separation of hydrogen isotopes by low temperature preparative chromatography.Cryogenic preparative chromatography utilizes the difference in adsorption selectivity of hydrogen isotopes on the adsorbent material to achieve separation,including the difference in static saturated adsorption capacity and the difference in dynamic adsorption capacity,and the latter is more critical to the separation effect.Under the same temperature and pressure conditions,the adsorption capacity,adsorption affinity,and adsorption rate of D2 over H2 on the molecular sieve were higher.The axial temperature gradient distribution of the separation column can promote the hydrogen isotope to undergo repeated adsorption and desorption processes.The local saturation,mass transfer,and desorption stages in the column are alternately changed,which greatly promotes the accumulation of hydrogen isotope separation effects.There are many factors affecting hydrogen isotope separation on cryogenic preparative columns.In addition to being influenced by conventional scrubbing chromatography factors,the separation system must be designed and operated in such a way that the hydrogen isotope adsorption thermal effect that can cause changes in the temperature field or column flow,and the column equivalent thermal conductivity,adsorption material filling porosity distribution,cyclic sampling methods and other factors were investigated.(2)An experimental research system for the separation and detection of hydrogen isotopes by low temperature preparative chromatography was designed.The adsorption properties of the packing material in the chromatographic column were characterized,and multiple cycles of saturated adsorption and desorption experiments were carried out.The experimental results show that the saturated adsorption capacity of the separation column is greatly affected by the carrier gas flow rate and the filling porosity in the column.A higher carrier gas flow rate will cause hydrogen isotopes to quickly penetrate the column,greatly reducing the adsorption capacity,and the porosity.A higher level will result in a much larger amount of actual adsorption than theoretically estimated adsorption capacity.The temperature gradient control during the desorption of the separation column can obtain better separation effect of hydrogen isotope.The hydrogen isotope desorption and elution curves show a trailing type distribution.The H2/HD enrichment stage is obvious,and the HD concentration effect is good.(3)A gradient isothermal separation hydrogen isotope experiment was conducted to investigate the effects of hydrogen isotope separation under different temperature gradients and carrier gas flow rates.The experimental results show that the use of gradient heating method to control the temperature change of the separation column can effectively promote the separation of hydrogen isotopes.The elution curve after isotope desorption shows a trailing peak distribution,and the degree of tailing of D2 is more serious than that of H2.1)The heating rate of the separation column has a great influence on the hydrogen desorption separation.The slower the heating rate,the longer the retention time of the hydrogen in the separation column and the longer the desorption process,and the longer the desorption time of the hydrogen peak,H2/D2 separation.The better the degree;2)The flow rate of the carrier gas has a certain influence on the hydrogen isotope desorption separation.The slower the flow rate,the longer the total retention time of the hydrogen isotope in the separation column and the longer the desorption process,and the longer the duration of the hydrogen desorption flow,The better the degree of separation of H2/D2 is;3)The method of gradient heating of the separation column along the direction of the gas flow is selected.The temperature increase step-by-step can achieve a gradient temperature field with a smaller temperature difference range than the entire temperature range,and the total length of the controlled desorption process can be obtained.Longer,but better to promote the separation of hydrogen isotopes.