吸附温度低于273K的Pd/k柱TCAP全回流实验研究

TCAP Total Reflux of Hydrogen Isotopes in Pd/k Column With Absorption Temperature Below 273 K

为满足实验室规模的氢同位素分离需求,对少量氚(小于3.7×1013 Bq)的高效氢同位素分离方法进行了研究。采用TCAP全回流工艺,将钯/硅藻土(Pd/k)填充色谱柱(长2m,外径6mm)吸附H-D混合气体(D丰度为50%)的温度控制在273K以下,经多次加热-冷却循环后,从分离柱前、后两端加热各提取15%样品气,利用低温色谱法对样品气进行氢同位素丰度分析,对色谱柱的分离性能进行评价。研究结果发现,原料气进入填充柱后(全回流之前)尾端提取气的氘丰度约为98.5%,经5个全回流循环(循环总时间为1.25h)后,尾端提取气的氘丰度达99.9%。经15个全回流循环后,前端提取气的氘丰度由50%(原料气氘丰度)降至13.6%。通过实验数据对柱中氘分布进行了理论模拟,发现进样速率过快可能是导致前端提取气氘丰度过高的主要原因,柱中氘丰度最低点可能出现在色谱柱的中部。

For high efficient hydrogen isotope separation in lab-scale application,a palladium/kieselguhr（Pd/k） column（2 m in length） was made.Ethanol was applied as liquid heat transfer medium to cool the Pd/k column below 273 K.TCAP total reflux experiments with different cycles were carried out to test the separation efficiency of the column.Hydrogen isotope mixtures（15% of total column content） were withdrawn both from the bottom and top end after each test.D concentration of the mixtures was tested by cryogenic chromatography.Results show that D concentration in the bottom section rises from 50% to 98.5% at the initial charge before reflux cycling.High purity（99.9%） deuterium is obtained after only five cycles（1.25 h）.D concentration in the top section drops from 50% to 13.6% after 15 cycles.Through a simulated D distribution model,fast flow rate through the top section may obviously reduce separation efficiency.The lowest D concentration is found near the middle of the column,and the raffinate with high H concentration will be achieved in the middle position.