| Separation of hydrogen isotope with palladium alloy membranes has been regarded as one of the promising methods for hydrogen isotope separation. It has several advantages, such as high separation efficiency, smaller tritium inventory, simple separation device, ect. Limited by the manufacture of membrane and cost of gas transportation pump, this method is still at the stage of conceptual study. The relationship between separation factors and temperatures, feed gas components, split ratios have not been researched in detail, and the calculated results of cascade separation have not been validated with experimental data. In this thesis, a palladium alloy membrane separator was designed to further study its separation performance between H2 and D2. Based on the experiment results, the model of cascade system was also set up.The permeation flux of H2 and D2 through the separator, as one of the decisive factors affecting the separator's scale, was investigated at the temperature from 573K to 873 K and pressure from 0.05 MPa to 0.40 MPa . The permeation flux of H2 and D2 was a half power relationship to the pressure approximately, and the permeability to temperature could be described with an Arrhenius-type relationship in which where ΦH=3.847×10-6 exp(-595.4/T) mol/m.s.Pa0.5,ΦD=3.870×10-6 exp(-937.0/T)mol/m.s.Pa0.5.The separation factor of the single stage was affected by the temperature, the feed gas component, the split ratio and the gas flow rate, etc. The experimental results showed that the H2-D2 separation factor decreased with the increasing of temperature. On the temperature from 573K to 773 K, when the feed rate was 5L/min, the separation factor of 66.2%H2 -33.8%D2 decreased from 2.09 to 1.85 when the split ratio was 0.1 and from 1.74 to 1.52 when the split ratio was 0.2.The separation factor also decreased with the increasing of split ratio. At 573K and the feed rate of 5L/min, the separation factor of 15.0%H2 and 85.0%D2 decreased from 2.43 to 1.35 with the increasing of split ratio from 0.050 to 0.534,and for 66.2%H2-33.8%D2, the separation factor decreased from 2.87 to 1.30 with the increasing of split ratio from 0.050 to 0.688.When the separation factor was the biggest, the flow rate of feed gas was in a perfect value. To gain a best separation performance, perfect flow rate, lower temperature and reflux ratio should be chosen.The ideal model and approximate model were set up to predict the separation efficiency of cascade separation system. The ideal model, not considering of the gases back from the next stages, showed that the number of separator was associated with the separation factor of the single stage: the bigger the separation factors, the less number of separators were needed.For example, to get the product with 0.05% H2-99.5%D2 from 10%H2-90%D2, the stage number was 8 when the separation factor was 2.5, and it was 14 when the separation factor was 1.47.However, the approximate model, considering the gases back from the next stage, showed that the gaseous hydrogen isotopes with 0.065% (V/V) tritium would be split into a product gas with 1.5% tritium and a waste gas with 0.0005% tritium after 3 enrichment stages and 4 stripping stages when the split ratio was 0.2 with a separation factor of 2.5 in all separation stages. The scale of the cascade separation system changes with the split ratio of each of the separators, the smaller the split ratio, the smaller the scale of the hydrogen isotope separation system.The results of the separation experiments on the single separator and the calculations of cascade separators indicate that the palladium alloy membrane separator cascade method is both reasonable and practicable for a large-scale hydrogen isotope separation. |
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